Umbilical cord blood (UCB) provides a rich source of stem cells for transplantation after myeloablative therapy. One major disadvantage of UCB transplantation is delayed platelet engraftment. We propose to hasten platelet engraftment by expanding the number of megakaryocyte (MK) precursors (CD34/CD41 cells) through cytokine stimulation within a closed, pre-clinical liquid culture system. Clinical engraftment data suggest a 5- to 10-fold increase in MK precursors in a UCB unit can accelerate platelet engraftment, so this was our goal. Thirteen UCB samples from full-term births were Ficoll-separated and frozen for subsequent use. On thawing, the mononuclear cell population was positively selected for CD34(+) expression. The cells were cultured in gas-permeable Teflon-coated bags in serum-free medium containing the following cytokines: recombinant human interleukin-3, recombinant human Flt3 ligand, recombinant human stem cell factor, and recombinant human thrombopoietin. MK lineage cell expansion was assessed using mononuclear cell count and flow cytometry (CD34/41, CD41, CD34/61, and CD61 expression) on days 7, 11, and 14. Optimal expansion of CD34/41 and CD41 cells was observed at day 11, with a median 6-fold and 33-fold increase in the starting cell doses, respectively. CD34/61 and CD61 cell expansion at day 11 was 7-fold and 14-fold, respectively. MK precursors can be successfully expanded from CD34(+) UCB cells in a closed liquid culture system using interleukin-3, recombinant human Flt3 ligand, recombinant human stem cell factor, and recombinant human thrombopoietin to a level that should have a clinical impact in the transplantation setting. Our ex vivo expansion technique needs to be further optimized before it can be used in a pilot UCB transplantation trial.

The purpose of this study was to monitor platelet activation by following alpha IIb beta 3 integrin (GpIIb/IIIa complex or CD41/CD61) on the platelet surface by flow cytometry (FCM) analysis using workshop mAbs. The results obtained with the mAbs showed increased expression of the GpIIb/IIIa complex (about 40%) on the platelet membrane surface under thrombin stimulation.

The aim of this research was to evaluate the effect of polyethylene terephthalate (Woven Dacron) on the expression of endothelial integrins. Human umbilical vein endothelial cells were cultured on the material for 24 h. The integrins VLA-2 (alpha2beta1-CD49b/CD29), receptor for laminin and collagen, VLA-5 (alpha5beta1-CD49e/CD29), receptor for fibronectin, VLA-6 (alpha6beta1-CD49f/CD29), receptor for laminin, and alphaVbeta3-CD51/CD61 (receptor for vitronectin) were evaluated by flow cytometry. After contact with polyethylene terephthalate, a slight but significant decrease in the percentage of both CD29 and CD49e positive cells was observed, which suggests a lower number of cells expressing the fibronectin receptor alpha5beta1. Moreover, a significant increase in the mean channel for CD49b and for the vitronectin receptor CD51/CD61 was observed. The reduction in the fibronectin receptor could account for the poor endothelialization observed in vivo on polyethylene terephthalate. The increased expression of the vitronectin receptor, favoring the migration of smooth muscle cells, could give some information about the pathogenesis of intimal hyperplasia, which is a complication of vascular grafts.

Callithrix jacchus, the common marmoset, is particularly suitable for immunological studies in vivo and in vitro since many antibodies directed against epitopes of human cells do also react with their analogues from this non-human primate. We studied the reactivity of antibodies against human epitopes on primary cultures of thymic epithelial cells from marmosets and humans by flow-cytometry after different culture periods. The antibodies against integrins, including CD61, reacted with thymic epithelial cells from both humans and marmosets, as did anti-CD44 and anti-CD106. Antibodies specific for thymic epithelial cells (TE-3, TE-4, TE-8, TE-15, TE-16, TE-19) also bound to cells from marmosets but expression of all epitopes was not observed in all cultures studied. The expression of CD51, CD54, CD58 and CD106 on human cells declined after 4 weeks of culture. Our findings indicate that marmosets are a valuable model for immunological studies of effects of xenobiotics on the thymic epithelium.

BACKGROUND

The protein SNAP-23 is part of the secretory pathway in platelets. It is, however, not entirely clear to what extent this protein contributes to the secretory function of platelets. Therefore, we overexpressed a dominant negative mutant with a novel technology that allows the creation of intact transgene-expressing platetets.

RESULTS

Overexpression of a dominant negative SNAP-23 mutant that inhibited the binding of the native protein to the docking site within the secretory machinery resulted in significant suppression of the agonist-dependent surface recruitment of P-selectin and CD40L. Simultaneously, release from dense granules was clearly suppressed in the presence of this construct. Also agonist-dependent surface expression of fibrinogen receptor markers CD41 and CD61 was reduced, and agonist-triggered aggregation was inhibited.

CONCLUSIONS

The dominant negative inhibition of SNAP-23 resulted in clear effects on platelet functions. The novel method using recombinant culture-derived platelets allowed the rapid clarification of the functional importance of this protein in intact platelets.

This study was to investigate dynamics of biological properties of CD133(+) cells from human umbilical cord blood (UCB) during short-term culture containing the combination of hematopoietic growth factors and the feasibility of in vitro expansion of CD133(+) cells. The biology activities including analysis of cell cycle, immunophenotype, telomerase activity, expression of adhesion molecules and expansion potential of CD133(+) cells were monitored during ex-vivo expansion, and compared with those of CD34(+) cells. The results showed that the contents of CD133(+) and CD34(+) cells in fresh UCB were (1.05 +/- 0.73)% and (1.40 +/- 0.56)% respectively. About 79.62% of CD34(+) cells expressed CD133, and more than 97% of CD133(+) cells were CD133(+)CD34(+), markedly higher than that in CD34(+) fraction (P < 0.01). No significant differences were observed in content of cells expressing CD38, CD13, CD14, CD61 and glycophorin-A between the two fractions. Expansion of CD133(+), CD133(+)CD34(+) and CD34(+)CD38(-) cells at 10 days and those of CFU-mix, HPP-CFC and CD34(+)CD38(-) cells at 6 days from CD133(+) cells group were significantly higher than those from the CD34(+) cell group (P < 0.05). Analysis of immunophenotype showed that CD133(+)CD34(+) cells declined gradually while CD133(-)CD34(+) and CD133(-)CD34(-) cells increased during ex-vivo expansion; basal telomerase activities of fresh UCB CD133(+) and CD34(+) cells were low but significantly exceeded that of CD34(-) fraction (P < 0.05). At first week of expansion, telomerase activity was significantly upregulated, after two weeks, telomerase activity remarkably declined, and decreased to baseline or below the limits of detection in day 20. More than 90% of CD133(+) cells expressed CD49d and CD11a, and, more than 85% of the cells expressed CD54, about 50% of cells expressed CD62L. At the early stage of expansion, expression of CD49d was upregulated, expression of CD11a remaining no change, while as expression of CD54 and CD62L was downregulated. Expression of all adhesion molecules was decreased gradually with extend of culture. But expression of these adhesion molecules on CD34(+) subsets were not affected significantly during expansion. It is concluded that CD133(+) population may be a more primitive hematopoietic stem/progenitor cells (HSPC) than CD34(+) cells, CD133(+) cells have great expansion potential for ex-vivo expansion and is a suitable target cell for ex-vivo expansion of HSPC. Downregulation of adhesion molecules and telomerase activity may be one of the reasons for delayed engraftment of expanded products.

The expression of several adhesion surface receptors was studied on cells of early limb bud development of 58 Wistar rats treated orally with two daily doses of the thalidomide derivative EM12 (2 x 50 mg/kg body weight) from day 7 to 10 of pregnancy. EM12 is a more potent teratogen than thalidomide. Limb bud cells of 56 untreated animals served as controls. The studies revealed that the integrins CD11a, CD11b, CD18, CD49d, and CD61, as well as the additional adhesion receptors CD54, CD62L, and the transferrin receptor CD71 were expressed on day 11 of gestation to various degrees on these embryonic cells. In contrast to results of previous studies with a non-human primate (Callithrix jacchus) there was no down-regulation of any of these receptors on the surface of limb bud cells of the rat embryos after treatment with EM12. This result is in accordance with the lack of teratogenicity in this rodent species.

The purpose of the study was to identify a unique immunophenotype of normal or Philadelphia chromosome positive (Ph+) CD34+ cells that might be used to purify normal CD34+ cells from chronic myelogenous leukemia (CML) patients. An immunophenotypical study of CD34+ bone marrow cells of 20 patients with CML at diagnosis and during hydroxyurea treatment, and 39 controls were performed. All patients were Ph+, two patients had variant translocations and three patients displayed cytogenetic signs of clonal evolution. The immature progenitor cell compartment (CD34+ HLA-DR- and CD34+ CD38- cells) was comparable. The CD34+ AC133+ progenitor cell compartment was decreased in CML patients. We found no difference for any of the adhesion molecules examined except for CD62L, where the percentage of CD34+ CD62L+ cells was decreased in CML patients. The number of myeloid progenitors (CD34+ CD33+) was increased at the expense of B-lymphoid progenitors (CD34+ CD10+ and CD34+ CD19+) in CML patients indicating that B-lymphopoiesis is inhibited in CML. The megakaryocytic (CD34+ CD61+) and erythroid (CD34+ CD71+) progenitors were increased in CML patients. The number of CD34+ CD7+ cells was also significantly increased (mean 25.3% vs. 4.9%). However, the level of CD7 expression was quite heterogeneous, and the patients could be separated into two populations according to CD7 expression (more or less than 20% CD7+ CD34+ cells). The Sokal and Hasford risk scores did not differ between CD34+ CD7- CML and CD34+ CD7+ CML, but all patients with signs of disease progression clustered in the CD34+ CD7+ population indicating that the level of CD7 expression on CD34+ cells may be of prognostic importance in CML.

Aims The aetiology for reduced thrombogenicity of the Magmaris resorbable magnesium scaffold (RMS) when compared with the Absorb bioresorbable vascular scaffold remains unclear. We therefore investigated whether the Magmaris RMS has platelet-repelling properties by comparing its acute thrombogenicity with an equivalent stainless steel stent in an arteriovenous shunt model. Methods and Results An ex vivo porcine carotid jugular arteriovenous shunt was established and connected to Sylgard tubing containing the Magmaris RMS with sirolimus-eluting PLLA coating and an equivalent 316L stainless steel stent with sirolimus-eluting PLLA coating. Six shunts (2 shunt runs per pig) were run comparing the 2 scaffolds (n=9) in alternating order. Nested generalised linear mixed models were employed to compare variables between scaffold groups. Confocal fluorescent microscopy costaining CD61/CD42b demonstrated that the 316L equivalent stent had significantly greater platelet coverage of the total scaffold compared with Magmaris (5.8% vs. 2.8%, Rate ratio 2.21 [1.41, 3.47], p=0.012). Scanning electron microscopy demonstrated significantly greater thrombus deposition on the 316L equivalent stent as a percentage of the total scaffold compared with Magmaris (8.0% vs. 5.3%, p=0.009). Magmaris also had significantly less CD14 positive monocyte deposition and a trend toward less PM-1 positive neutrophil compared with the 316L equivalent stent. Conclusion Despite having identical scaffold characteristics regarding geometrical design, Magmaris had significantly less thrombogenicity and inflammatory cell deposition compared with the equivalent 316L stainless steel stent in a porcine arteriovenous shunt model. These data suggest resorbable magnesium scaffolds may have inherent properties that reduce adhesion of platelets and inflammatory cells.

Essential thrombocythemia is associated with an increased risk of thromboembolic complications. Recently, there has been a growing evidence that platelet-leukocyte interactions may contribute to pathogenesis of thrombosis in essential thrombocythemia. Low-dose aspirin (ASA) is generally recommended in the therapy of low-risk patients for thrombosis, whereas hydroxyurea in high-risk patients. The aim of the present study was to determine the effect of ASA and hydroxyurea on platelet, leukocyte functions and on formation of platelet/leukocyte conjugates in vivo in patients with essential thrombocythemia. Markers of platelet and leukocyte activation were assessed in 40 patients with essential thrombocythemia at diagnosis and in 20 controls using flow cytometry assays. In second part of the study, the tests were repeated after either ASA treatment (in 25 low-risk patients) or hydroxyurea therapy (in 15 high-risk patients). On diagnosis, significantly elevated expression of P-selectin on platelets (4.98 +/- 3.31 vs. 0.99 +/- 0.69 P < 0.001) and increased percentage of platelet-polymorphonuclear leukocyte CD11b/CD42b conjugates [10.12 (4.21-31.22) vs. 3.17 (1.43-5.99) P < 0.001] and platelet-monocyte CD11b/CD14/CD61 conjugates [36.62 (12.23-51.62) vs. 13.86 (7.14-23.51) P < 0.001] were found in essential thrombocythemia group as compared with the healthy control group. Therapy with ASA significantly reduced platelet-polymorphonuclear leukocyte [10.72 (4.21-26.97) vs. 8.12 (1.13-26.94) P < 0.05] and platelet-monocyte conjugates [38.6 (13.45-51.62) vs. 25.76 (13.52-45.02) P < 0.05]. Surprisingly, therapy with hydroxyurea was poorly effective in reduction of platelet/leukocyte conjugates. These data document an increased platelet and leukocyte activation at the time of diagnosis. This is the first report showing enhanced platelet-leukocyte aggregate formation in low-risk essential thrombocythemia patients and the efficacy of ASA in its reduction.

BACKGROUND

Chronic drug abuse is an established cause of acute coronary events and sudden death. The association between use of narcotics and platelet abnormalities is well described. However, it is still not clear, how aspirin affects expression of major platelet receptors in chronic drug users with coronary artery disease, especially those recovering in the methadone clinic maintenance program. We sought to compare how a single pill of non-enteric coated aspirin (325-mg) affects human platelets in patients with coronary artery disease dependent on methadone use.

METHODS

Data from 30 subjects were analyzed, eight of them were the chronic drug addicts, and participated in a methadone recovery program. Platelets were assessed twice at baseline (pre-aspirin), and after 3-24 hours (post-aspirin). The expression of platelet receptors was determined by using the following monoclonal antibodies: CD31 (PECAM-1), CD41 (GPIIb), CD42b (GPIb), CD51/CD61 (vitronectin receptor), CD62p (P-selectin), CD63 (LIMP or LAMP-3), CD107a (LAMP-1), CD151 (PETA-3), and PAC-1 for fibrinogen-platelet binding determination (PharMingen, San Diego, CA). Platelet-leukocyte interactions were assessed by using dual antibodies for a pan-platelet marker (CD151), together with CD14, a monocyte/macrophage marker.

RESULTS

In a drug free group, digestion of a single tablet of aspirin resulted in a significantly (p<0.05) diminished expression of PECAM-1, GP IIb, fibrinogen binding with PAC-1 antibody, GP Ib, P-selectin, and CD151. In contrast, patients receiving methadone exhibited opposite trends, resultant in a paradoxical activation of major platelet receptors after digestion of aspirin. These differences reached statistical significance (p<0.05) for PECAM-1, GPIIb, and P-selectin expression.

CONCLUSIONS

There are some fundamental differences in the responsiveness to aspirin in chronic methadone users when compared with drug-free patients. Suspecting narcotics abuse may be critical in patients with limited aspirin efficacy, or those who developed an aspirin resistance. Unexpected platelet activation may indeed represent a missing link between use of narcotics and enhanced incidence of vascular death in this high-risk population.

CD34+ progenitor cells are growing in use for vascular repair. However, in diabetic individuals with cardiovascular diseases, these cells have dysfunctional engraftment capabilities, which compromise their use for autologous cell therapy. The thrombospondin-1-derived peptide RFYVVMWK has previously been reported to stimulate cell adhesiveness through CD47 and integrin activation pathways. Our aim was to test whether RFYVVMWK preconditioning could modulate CD34+ cell phenotype and enhance its proadhesive properties in diabetic patients. Peripheral blood mononuclear CD34+ cells isolated from 40 atherosclerotic patients with type 2 diabetes (T2D; n = 20) or without (non-T2D; n = 20) were preconditioned with 30 μM RFYVVMWK or truncated peptide RFYVVM. CD34+ cell adhesion was assessed on a vitronectin-collagen matrix and on TNF-α or IL-1β-stimulated HUVEC monolayers. Adhesion receptors, platelet/CD34+ cell conjugates, and cell viability were analyzed by flow cytometry and confocal microscopy. RFYVVMWK increased the adhesion of T2D CD34+ cells by eightfold to the vitronectin-collagen matrix (p < 0.001) corresponding to a threefold increase compared to unstimulated non-T2D CD34+ cells. The peptide induced the formation of platelet/CD34+ conjugates and increased the expression of TSP-1, CD29, CD51/CD61, and CD62P in both T2D and non-T2D cells. However, RFYVVMWK treatment did not affect the viability/apoptosis of CD34+ progenitor cells. In conclusion, priming CD34+ cells with RFYVVMWK may enhance their vascular engraftment during autologous proangiogenic cell therapy.

OBJECTIVE

The use of ex vivo expanded cells has been suggested as a possible means to accelerate the speed of engraftment in cord blood (CB) transplantation. The aim of this study was to fix the optimal condition for the generation of committed progenitors without affecting the stem cell compartment.

METHODS

Analysis of the effects of FLT3-L and MIP-1alpha when combined with SCF, IL-3 and IL-6, in short-term (6 days), serum-free expansion cultures of CB-selected CD34+ cells.

RESULTS

An important expansion was obtained that ranged between 8-15 times for CFU-GM, 21-51 times for the BFU-E/CFU-Mix population and 11 to 30 times for CD34+ cells assessed by flow cytometry. From the combinations tested, those in which FLT3-L was present had a significant increase in the expansion of committed progenitors, while the presence of MIP-1alpha had a detrimental effect on the generation of more differentiated cells. However, stem cell candidates assessed by week 5 CAFC assay could be maintained in culture when both MIP-1a and FLT3-L were present (up to 91% recovery). This culture system was also able to expand megakaryocytic precursors as determined by the co-expression of CD34 and CD61 antigens (45-70 times), in spite of the use of cytokines non-specific for the megakaryocytic lineage.

CONCLUSIONS

The results obtained point to the combination of SCF, IL-3, IL-6, FLT3-L and MIP-1alpha as the best suited for a pre-clinical short-term serum-free static ex vivo expansion protocol of CB CD34+ cells, since it can generate large numbers of committed progenitor cells as well as maintaining week 5 CAFC.

The mechanisms of platelet underproduction in immune thrombocytopenia (ITP) remain unknown. While the number of megakaryocytes is normal or increased in ITP bone marrow, further studies of megakaryocyte integrity are needed. Megakaryocytes are responsible for the production of platelets in the bone marrow, and they are possible targets of immune-mediated injury in ITP. Since the biological process of megakaryocyte apoptosis impacts platelet production, we investigated megakaryocyte DNA fragmentation as a marker of apoptosis from ITP bone marrow biopsies. Archived bone marrow biopsy specimens from ITP patients, bone marrow specimens from controls with normal platelet counts, and bone marrow specimens from thrombocytopenic controls with myelodysplastic syndrome (MDS) were evaluated. Sections were stained with anti-CD61 for megakaryocyte enumeration, and terminal deoxynucleotidyl transferase dUTP nick-end labeling was used as an apoptotic indicator. In ITP patients, megakaryocyte apoptosis was reduced compared to nonthrombocytopenic controls. Megakaryocyte apoptosis was similarly reduced in thrombocytopenic patients with MDS. These results suggest a link between megakaryocyte apoptosis and platelet production.

Integrin (alpha)IIb(beta)3 (abbreviated as (alpha)IIb), also known as GPIIb-IIIa or CD41/CD61, is a cell adhesion molecule expressed on cells belonging to the megakaryocytic lineage. Aiming to identify new markers of hemopoietic progenitor cells (HPC), we undertook a developmental study of this molecule since it remains controversial if this integrin is expressed by various progenitors. We reported the expression pattern of two integrins, in both of which the beta3 chain is present, respectively associated with alphaV and alpha IIb in the chick embryo. While at E3.5, the earliest time at which these integrins can be detected, (alpha)V(beta)3 becomes expressed by endothelial cells in the aorta (and only in the aorta), (alpha)IIb(beta)3 becomes detected in the well-defined intra-aortic clusters made up of HPC. The latter were found to be multilineage progenitors when sorted for (alpha)IIb expression and analyzed by means of clonogenic assays. In mice also, (alpha)IIb is expressed in the intra-embryonic site of HPC generation, the intra-arterial clusters in the embryo proper, as well as in sites where HPC migrate. Finally we provided the first evidence in two species that multipotent HPC expressing (alpha)IIb are able to differentiate not only into cells of the erythroid and myeloid lineages but also into lymphocytes. These cell populations actually coexpress (alpha)IIb and c-Kit. These data establish (alpha)IIb as a novel marker for HPC, which appears at very early stages in the embryo. Capitalizing on this finding, other investigators confirmed it and suggested that (alpha)IIb plays a role in regulating hematopoietic development.

A morphometric analysis of bone marrow trephine biopsies has been performed to study the frequency and planimetric characteristics of so-called atypical micromegakaryocytes in chronic myeloid leukemia (CML) and myelodysplastic syndromes (MDS). In addition, an attempt was made to discriminate this particular cell population from small immature elements of megakaryocytopoiesis, such as promegakaryoblasts and megakaryoblasts. The staining reactions employed included periodic acid-Schiff (PAS), alpha-naphthyl acetate esterase (ANAE) and immunohistochemistry with a monoclonal antibody against platelet glycoprotein IIIa (Y2/51-CD61). Comparison of the various staining reactions applied to the different megakaryocytic elements together with morphometric measurements resulted in a clearcut identification of promegakaryoblasts. These were defined as the earliest immature and exclusively CD61-positive precursors. Atypical micromegakaryocytes were characterized by their dysplastic features and strong ANAE reactivity in addition to their positive CD61 staining. When stringent diagnostic criteria (diameter ranging between 10 to 15 microns, mean size about 12 microns) were applied, this abnormal cell population comprised less than 10% of total megakaryocytopoiesis in CML and MDS. It may be assumed that dysmegakaryocytic features in the latter disorders are partially generated by small to medium-sized megakaryocytes (diameter less than 30 microns). In conclusion, the relative frequency of promegakaryoblasts in the normal bone marrow (range 6-8%) is confirmed by evaluation of the immunohistochemical and cytochemical staining methods (CD61 and ANAE). Furthermore, the ANAE reaction facilitates the recognition of atypical micromegakaryocytes as well as small megakaryocytes. Thus cytochemistry provides a better insight into alterations of these cell lineages in various pathological conditions.

The clinical, cytogenetic, and immunophenotypic features in 12 adult patients with acute panmyelosis with myelofibrosis (APMF; ICD-0-3: 9931/3; C42.1) are reported (median age: 57 years; f/m = 1.4). The white cell count (WBC) was normal in 3 patients; 9 had leucopenia. The median hemoglobin value was 64.5 g/l, and median platelet count 12 x 10(9)/l. Bone marrow biopsy showed a hypercellular marrow in 10/12 patients with a significant infiltration of pathological blasts (range: 30 - 60%). All the cases had marked reticulin fibrosis. Immunophenotyping of bone marrow blast cells showed the expression of early (CD34) and lineage-unspecified antigens (HLA-DR) in 6/7, and 7/7 patients, respectively. "Early" myeloid antigens (CD13, CD33) were seen in 6/7 and 4/6 patients respectively. Monocyte antigen (CD14) was expressed in 3/7 patients. Megakaryocyte antigen (CD61) and erythroid cell antigen (GpA) were each expressed in only 1 patient. Two patients had expression of CD34, HLA-DR and "early" myeloid antigens by their bone marrow blast cells and 1 of these also had a co-expression of the antigens from a differentiated monocytic cell proliferation (lysozyme+, CD68+). Nonspecific chromosomal aberrations were recorded in 8/10 patients. The median survival was 2 months. These findings suggest an immature myeloid phenotype of blast cells in APMF. In 6/9 patients a leukemic cell differentiation into monocytic, megakaryocytic or erythroid lineage was also demonstrated.

Extramedullary hematopoiesis occurring in the myocardium has previously only been reported in a single case of a neonate with cyanotic congenital heart disease. Herein we report the incidental discovery of extramedullary hematopoiesis or pure erythropoiesis in four failing adult hearts with myocardial infarction. In two cases, extramedullary hematopoiesis or erythropoiesis was identified in cardiectomy specimens removed at orthotopic heart transplantation; in two other cases, erythropoiesis was found in left ventricular tissue removed at the time of implantation of left ventricular assist devices. Myocardial hematopoiesis/erythropoiesis was identified based on characteristic light-microscopic findings in routinely processed tissue and was confirmed by immunhistochemistry using monoclonal antibodies to the erythroid cell marker glycophorin A (positive in all cases), the megakaryocyte marker CD61, and the granulocyte marker neutrophil elastase (the latter two markers positive in one case only). None of the four patients had a myeloproliferative disorder or evidence of a myelophthisic process. No hematopoietic elements were identified in 109 cardiectomy specimens without acute or recent infarcts. Myocardial hematopoiesis or erythropoiesis could represent heretofore-unrecognized manifestations of altered cytokine expression in patients with heart failure due to myocardial infarction.

The actual mechanisms underlying severe bleeding in dengue hemorrhagic fever (DHF) are not completely understood. The immune mimicking theory is a widely mentioned hypothesis that might help answer questions. In this study, the author performed a prediction on the binding affinity on the NS1 immunoglobulin (IgG and CD61-IgG) complexes using a computation medicine technique. According to this study, the significant discrimination of modeled Ig complexes can be detected. The finding, which is expected for the late recovery phase of dengue, implies the difficulty in mimicking immune complex formation.

Patients with bronchial asthma develop various types of asthmatic response to bronchial challenge with allergen, such as immediate/early asthmatic response (IAR), late asthmatic response (LAR) or delayed asthmatic response (DYAR), because of different immunologic mechanisms. The DYAR, occurring between 24 and 56 hours after the bronchial allergen challenge (p < 0.01), differs from IAR and LAR in clinical as well as immunologic features. This study investigates the expression of CD molecules (markers) on the surface of particular cell populations in the peripheral blood and their changes during the DYAR. In 17 patients developing the DYAR (p < 0.01), the bronchial challenge with allergen was repeated 2-6 weeks later. The repeated DYAR (p < 0.001) was combined with recording of CD molecule expression on various types of blood cells by means of flow cytometry up to 72 hours after the challenge. The results were expressed in percent of the mean relative fluorescence intensity. The DYAR was accompanied by (a) increased expression of CD11b, CD11b/18, CD16,CD32, CD35, CD62E, CD62L, CD64, and CD66b on neutrophils; CD203C on basophils; CD25 and CD62L on eosinophils; CD14, CD16, CD64, and CD86 on monocytes; CD3, CD4, CD8, CD11a, CD18, and CD69 on lymphocytes; CD16, CD56, CD57, and CD94 on natural killer (NK) cells; and CD31, CD41, CD61, CD62P, and CD63 on thrombocytes and (b) decreased expression of CD18 and CD62L on eosinophils, CD15 on neutrophils, and CD40 on lymphocytes. These results suggest involvement of cell-mediated hypersensitivity mechanism, on participation of Th1- lymphocytes, neutrophils, monocytes, NK cells, and thrombocytes in the DYAR.

We report a case of pediatric acute megakaryocytic leukemia (AMKL) showing 48,XX,+21,+21 as a sole acquired cytogenetic abnormality without the mutation of GATA1 gene. A physical examination showed a phenotypically normal female. Bone marrow findings showed diffuse infiltration of leukemic blasts having scanty cytoplasm with budding blebs and prominent nucleoli, which were negative for myeloperoxide (MPO) stain, Sudan black B stain and periodic acid-Schiff stain. Immunophenotyping of leukemic cells revealed positive expression of CD34, CD13, CD33, CD117, CD41, CD61, CD7 and negative expression of TdT, anti-MPO, CD64, CD56, CD2, CD3, CD5, CD10, CD19, CD20 and CD22. A fluorescence in situ hybridization analysis showed four distinct AML1 signals in 284 of 300 interphase nuclei. The entire six exons of the GATA1 gene (7757bp) were directly sequenced. We could not find any mutations, including known polymorphisms, which are known to be involved in transient myeloproliferative disorder and acute megakaryocytic leukemia of Down syndrome. After achieving complete remission, the tetrasomy 21 disappeared.

The expression of adhesion molecules on blasts from 14 patients with acute myeloid leukemia (AML) was investigated by immunofluorescence and flow cytofluorometry. All tested blast populations expressed CD18/CD11a complex [leukocyte function antigen-1 (LFA-1)] and CD29 (very-late antigen (VLA)) and the majority were positive for CD54 [intercellular adhesion molecule-1 (ICAM-1), 78.6%] and CD56 [neural cell adhesion molecule (NCAM), 64.3%]. The expression of two other alpha chains of CD18/CD11b and CD11c varied considerably (64.3% and 42.8% of positive cases, respectively). Only one case (AML-M4) showed a weak expression of the activated platelet antigen CD41b. None of the tested blasts expressed the vitronectin receptor (CD61/CD51). No significant correlation between the expression of adhesion molecules and the FAB type of leukemia could be found. All tested blast populations were completely resistant to NK-mediated cytotoxicity and relatively resistant to LAK-mediated cytotoxicity in the standard 51Cr release assay. While no statistically significant correlation of the results in cytotoxicity assays with the expression of adhesion molecules or the expression of HLA-DR antigen could be observed, 2 out of 3 completely resistant cases lacked ICAM-1. These results show that even leukemic blasts which express all of the tested adhesion molecules can still be resistant to LAK-mediated cytotoxicity.

Hematopoiesis is a complex process regulated by sets of transcription factors in a stage-specific and context-dependent manner. THAP11 is a transcription factor involved in cell growth, ES cell pluripotency, and embryogenesis. Here we showed that THAP11 was down-regulated during erythroid differentiation but up-regulated during megakaryocytic differentiation of cord blood CD34+ cells. Overexpression of THAP11 in K562 cells inhibited the erythroid differentiation induced by hemin with decreased numbers of benzidine-positive cells and decreased mRNA levels of α-globin (HBA) and glycophorin A (GPA), and knockdown of THAP11 enhanced the erythroid differentiation. Conversely, THAP11 overexpression accelerated the megakaryocytic differentiation induced by phorbol myristate acetate (PMA) with increased percentage of CD41+ cells, increased numbers of 4N cells, and elevated CD61 mRNA levels, and THAP11 knockdown attenuated the megakaryocytic differentiation. The expression levels of transcription factors such as c-Myc, c-Myb, GATA-2, and Fli1 were changed by THAP11 overexpression. In this way, our results suggested that THAP11 reversibly regulated erythroid and megakaryocytic differentiation.

Platelets play a role in both the innate and adaptive immune systems. Methods for detecting activated platelets and leukocyte-platelet aggregates (LPAs) are useful for basic and applied research concerning the role of platelets in inflammation and immune disorders. The aim of the study was to develop flow cytometric assays for detection of platelets binding to monocytes and neutrophils and for activated platelets in canine whole blood and to investigate the effect of physiologic agonists. Citrate anticoagulated whole blood was incubated with monoclonal antibodies against CD14 and CD61 for detection of LPAs, and the effect of various agonists was investigated. For detection of activated platelets, whole blood was incubated with monoclonal antibodies against CD62P and against a receptor-induced binding site on fibrinogen (CAP1) with CD61 as a platelet identifier. Isotype controls were prepared in parallel. The individual physiologic agonists ADP, collagen and epinephrine increased LPAs, CD62P and CAP1 binding only modestly. However, combinations of agonists gave more substantial increases. A dose-response relationship was seen using alpha- and gamma-thrombin, and ADP as agonists. In conclusion, we have developed flow cytometry assays to measure LPAs and platelet activation in canine whole blood, and have explored the effect of various physiologic agonists at different concentrations.