We postulated that changes in the cell surface display of molecules that facilitate cell-cell and cell-matrix adhesions may reflect the changing immunosurveillance capacity of blood monocytes during progression of human immunodeficiency virus (HIV) infections. In Centers for Disease Control (CDC) stage A patients, whose monocytes' ability to phagocytose bacteria and generate reactive oxygen intermediates is often increased, the frequency of monocytes expressing CD49d, HLA-DP, HLA-DQ, and an activation epitope of CD11a/CD18 was increased and monocyte transendothelial migration was unimpaired. In CDC stage B/C patients, whose monocytes' ability to phagocytose bacteria and migrate across confluent endothelial monolayers was diminished, surface expression of CD49e and CD62L and the percentage of monocytes expressing CD18, CD11a, CD29, CD49e, CD54, CD58, CD31, and HLA-I were significantly decreased. Incubating normal donor monocytes with immune complexes in vitro reproduced the phenotypic and functional abnormalities seen in stage B/C patients. By contrast, in vitro stimulation with subcellular particulates released by apoptotic lymphocytes reproduced changes seen in stage A patients' monocytes. Although circulating monocytes appear to be activated at all stages, these data suggest that the high levels of circulating immune complexes, found predominantly in the later stages of HIV infection, may be particularly instrumental in reducing the monocyte's capacity to maintain surveillance against infection.

Regulatory T-cells (T(Reg) cells) are increased in patients with multiple myeloma (MM). We investigated whether MM cells could generate and/or expand T(Reg) cells as a method of immuno-surveillance avoidance. In an in vitro model, CD4(+)CD25(-)FoxP3(-) T-cells co-cultured with malignant plasma cells (primary MM cells and cell lines) induced a significant generation of CD4(+)CD25(+)FoxP3(+) inducible T(Reg) cells (tT(Reg) cells; p<0.0001), in a contact-dependent manner. tT(Reg) cells were polyclonal, demonstrated a suppressive phenotype and phenotypically, demonstrated increased FoxP3 (p = 0.0001), increased GITR (p<0.0001), increased PD1 (p = 0.003) and decreased CD62L (p = 0.007) expression compared with naturally occurring T(Reg) cells. FACS-sorted tT(Reg) cells differentiated into FoxP(+)IL-17(+) and FoxP3(-)IL-17(+) CD4(+) cells upon TCR-mediated stimulation. Blocking experiments with anti-ICOS-L MoAb resulted in a significant inhibition of tT(Reg) cell generation whereas both IL-10 & TGFβ blockade did not. MM tumour cells can directly generate functional T(Reg) cells in a contact-dependent manner, mediated by ICOS/ICOS-L. These features suggest that tumour generation of T(Reg) cells may contribute to evasion of immune surveillance by the host.

Exposure to occupationally relevant concentrations of the environmental pollutant, trichloroethylene (TCE), in the drinking water of autoimmune-prone MRL+/+ mice has been shown to promote the generation of lupus and autoimmune hepatitis in association with the activation of Interferon-gamma (IFN-gamma)-producing CD4+ T cells. Since blocking TCE metabolism suppressed the TCE-induced alteration in immune function, the present study was initiated to determine whether the major metabolites of TCE, trichloroacetaldehyde hydrate (TCAH) and trichloroacetic acid (TCA) could also mediate these immunoregulatory affects in vivo. TCAH and TCA were administered to the drinking water of MRL+/+ mice for 4 weeks. CD4+ T cells from TCAH and TCA-treated MRL+/+ mice, unlike CD4+ T cells from control mice, demonstrated functional and phenotypic signs of activation, as evidenced by increased IFN-gamma production in association with the increased percentage of CD62L(lo) CD4+ T cells. Interestingly, it was also found that the CD4+ T cells from the TCAH and TCA-treated mice showed a decreased susceptibility to the activation-induced cell death (AICD) form of apoptosis following re-stimulation in vitro. By demonstrating that TCAH and TCA can activate CD4+ T cells and inhibit their apoptosis following in vivo exposure represents a mechanism by which environmental toxicants may induce or accelerate the development of autoimmune disease.

Th1 and Th17 cells have an established role in protective immunity to Bordetella pertussis, but this evidence is based largely on peripheral T cells. There is emerging evidence that local tissue-resident memory T (TRM) cells that accumulate in tissue following mucosal infection may be crucial for long-term immunity. In this study, we examined the role of respiratory CD4 TRM cells in immunity to B. pertussis Natural immunity to B. pertussis induced by infection is considered long lasting and effective at preventing reinfection. Consistent with this, we found that convalescent mice rapidly cleared the bacteria after reinfection. Furthermore, CD4 T cells with a TRM cell phenotype (CD44+CD62L-CD69+ or CD44+CD62L-CD69+CD103+) accumulated in the lungs of mice during infection with B. pertussis and significantly expanded through local proliferation following reinfection. These CD4 TRM cells were B. pertussis specific and secreted IL-17 or IL-17 and IFN-γ. Treatment of mice with FTY720, which prevented migration of T and B cells from lymph nodes to the circulation, significantly exacerbated B. pertussis infection. This was associated with significantly reduced infiltration of central memory T cells and B cells into the lungs. However, the local expansion of TRM cells and the associated rapid clearance of the secondary infection were not affected by treatment with FTY720 before rechallenge. Moreover, adoptive transfer of lung CD4 TRM cells conferred protection in naive mice. Our findings reveal that Ag-specific CD4 TRM cells play a critical role in adaptive immunity against reinfection and memory induced by natural infection with B. pertussis.

BACKGROUND

High-grade serous carcinoma (HGSC) of the ovary is predominantly diagnosed at late stages and primarily treated with debulking surgery followed by platinum/taxane-based chemotherapy. Although certain patients benefit significantly from currently used chemotherapy, there are patients who either do not respond or have an inadequate duration of response. We previously showed that tumours from chemoresistant patients have an immunosuppressed pre-existing tumour immune microenvironment with decreased expression of Type I Interferon (IFN1) genes.

METHODS

Efficacy of a 'STimulator of INterferon Genes' agonist was evaluated in combination with carboplatin chemotherapy and PD-1 immune checkpoint blockade therapy in the ID8-Trp53-/- immunocompetent murine model of HGSC.

RESULTS

Treatment with STING agonist led to decreased ascites accumulation and decreased tumour burden. Survival of mice treated with a combination of carboplatin, STING agonist and anti-PD-1 antibody was the longest. Tumour immune transcriptomic profiling revealed higher IFN response, antigen presentation and MHC II genes in tumours from STING agonist-treated mice compared to vehicle controls. Flow cytometry analysis revealed significantly higher intra-tumoural PD-1+ and CD69+CD62L-, CD8+ T cells in STING agonist-treated mice.

CONCLUSIONS

These findings will enable rational design of clinical trials aimed at combinatorial approaches to improve chemotherapy response and survival in HGSC patients.

T-helper type 2 (TH2) cells are one of the hallmarks of airway remodeling. The daunting task of regaining tolerance will be to regulate airway hyperresponsiveness (AHR) and remodeling in chronic asthma by balancing the ballet of TH1 and TH2 cells. The mechanism of tolerance appears to be modulated by a specialized subset of T cells called regulatory T cells (Tregs). Currently there are six subtypes of Tregs including CD4+CD25+ naturally occurring (N-Tregs), inducible naïve CD4+CD25- T cells (TR1), TR1 memory phenotype, T-helper type 3 (TH3), CD4-CD25+DX5+ natural killer T cells (TRNKT), and CD4-CD25+CD8+ cytotoxic T cells (TRCTC). The development of Tregs is controversial as to whether they occur in the thymus or peripheral lymphoid tissue. Studies have shown that NTregs are generated in the thymus and TR1 cells occur in the periphery. Nevertheless, Tregs express an arsenal of molecular membrane markers: CD3, CD25, CD62L, CD69, BTLA, GITR, ICOS, Neuroplin- 1 (Nrp-1), and PD-1. However, the most definitive marker is Forkhead Winged-Helix Transcriptional Factor Box p3 (Foxp3). The suppression of N-Tregs occurs by cell-to-cell contact, and low levels of IL-10 and moderate levels of TGF-beta, but the primary mechanism involves the sequestration and activation of neighboring naïve CD4+CD25- T cells to become TR1 cells. In contrast, TR1 cells exert their suppressive properties by copious secretion of IL-10 and TGF- beta. These suppressive mechanisms occur by the inhibition of IL-2 production and the promotion of cell cycle arrest. The development of this specialized subset of T cells is an enigma, but their understanding will provide a plausible panacea for asthma.

To study the role of T cells in gram-negative sepsis, we developed a mouse model in which i.v. injection of Escherichia coli results in severe systemic illness, with high mortality rates after day 5. A large proportion of both CD4(+) and CD8(+) T cells are activated within 1 day after infection, as evidenced by up-regulation of CD69 and down-regulation of CD62L. Even more surprisingly, T cell-deficient mice exhibit markedly decreased disease severity compared to WT mice, indicating a pathogenic role of T cells. Mice lacking IFN-gamma also show diminished disease, and exhibit reduced T cell activation. Therefore, the pathogenic role of T cells may be mediated by IFN-gamma. Both T cell- and IFN-gamma-deficient mice have reduced serum IL-6 levels compared to WT mice, suggesting that T cells may stimulate innate immune responses, resulting in enhancement of disease. These data indicate an important role for T cells in a mouse model of E. coli sepsis, and reveal an unexpected early and pathogenic T cell response to this bacterial infection.

Following natural infection with Bartonella, dogs and humans develop comparable disease manifestations including endocarditis, peliosis hepatis, and granulomatous disease. As the immunologic response to infection in these hosts has not been clearly established, data presented here was derived from the experimental infection of six specific pathogen free (SPF) beagles with a known pathogenic strain of Bartonella. Six dogs were inoculated intravenously with 10(9)cfu of B. vinsonii ssp. berkhoffii and six control dogs were injected intravenously with an equivalent volume of sterile saline. Despite production of substantial levels of specific antibody, blood culture and molecular analyses indicated that Bartonella established chronic infection in these dogs. Flow cytometric analysis of monocytes indicated impaired bacterial phagocytosis during chronic Bartonella infection. There was also a sustained decrease in the percentage of CD8+ lymphocytes in the peripheral blood. Moreover, modulation of adhesion molecule expression (downregulation of L-selectin, VLA-4, and LFA-1) on CD8+ lymphocytes suggested quantitative and qualitative impairment of this cell subset in Bartonella-infected dogs. When compared with control dogs, flow cytometric analysis of lymph node (LN) cells from B. vinsonii infected dogs revealed an expanded population of CD4+ T cells with an apparent naïve phenotype (CD45RA+/CD62L+/CD49D(dim)). However, fewer B cells from infected dogs expressed cell-surface MHC II, implicating impaired antigen presentation to helper T cells within LN. Taken together, results from this study indicate that B. vinsonii establishes chronic infection in dogs which may result in immune suppression characterized by defects in monocytic phagocytosis, an impaired subset of CD8+ T lymphocytes, and impaired antigen presentation within LN.

To study the phenotypic and functional changes in naive type II collagen (CII)-specific autoimmune T cells following a tolerogenic signal, a TCR-transgenic (Tg) mouse model of collagen-induced arthritis was developed. These Tg mice express an I-A(q)-restricted CII (260-267)-specific TCR that confers severe accelerated autoimmune arthritis following immunization with CII. Despite the fact that >90% of the alphabeta T cells express the Tg, these mice can be rendered completely tolerant to the induction of arthritis by i.v. administration of 200 microg of CII. As early as 24 h after CII administration, CII-specific T cells demonstrated a decreased ability to proliferate in response to the CII immunodominant peptide and phenotypically altered the expression of L-selectin to CD62L(low) and of phagocytic glycoprotein-1 to CD44(high), expression levels consistent with the phenotype of memory T cells. In addition, they up-regulated the expression of the activation markers CD71 and CD69. Functionally, following tolerogenic stimulation, the CII-specific T cells produced similar levels of IL-2 in comparison to controls when challenged with CII peptide, however, by 48 h after exposure to tolerogen, IL-2 production dropped and was replaced by high levels of IL-10 and IL-4. Based on their production of Th2 cytokines, these data suggest that T regulatory cells expressing activation and memory markers are induced by the tolerogen and may exert their influence via cytokines to protect the animals from the induction of arthritis.

The immunopathogenesis of AIDS-associated hepatitis was explored in the SIV/rhesus monkey model. The livers of SIV-infected monkeys showed a mild hepatitis, with a predominantly CD8+ T lymphocyte infiltration in the periportal fields and sinusoids. These liver-associated CD8+ T cells were comprised of a high percentage of SIV-specific CTL as defined by MHC class I/Gag peptide tetramer binding and Gag peptide epitope-specific lytic activity. There was insufficient viral replication in these livers to account for attracting this large number of functional virus-specific CTL to the liver. There was also no evidence that the predominant population of CTL were functionally end-stage cells trapped in the liver and destined to undergo apoptotic cell death in that organ. Interestingly, we noted that liver tetramer-binding cells showed an increased expression of CD62L, an adhesion molecule usually only rarely expressed on tetramer-binding cells. This observation suggests that the expression of specific adhesion molecules by CTL might facilitate the capture of these cells in the liver. These results demonstrate that functional SIV-specific CD8+ T cells are present in large numbers in the liver of chronically SIV-infected monkeys. Thus, the liver may be a trap for virus-specific cytotoxic T cells.

Two functionally different memory T cell subsets were originally defined based on their different CCR7 expression profile, but the lineage relationship between these subsets referred to as central memory T cells (T(CM)) and effector memory T cells (T(EM)), is not resolved. A prevalent model proposes a linear progressive differentiation from T(CM) to T(EM). Our results demonstrate that on activation, human CCR7-CD62L- peripheral blood CD8+ and CD4+ T(EM) cells exhibit a dynamic differentiation, involving transient as well as stable changes to T(CM) phenotype and properties. Whereas the larger fraction of T(EM) cells increases expression of effector molecules, such as perforin or IFN-gamma, a smaller fraction first acquires CCR7 expression. We demonstrate that this acquisition of lymph node homing potential is associated with strong proliferation similar to that of activated T(CM) cells. After proliferation, most of these cells lose CCR7 expression again and acquire effector functions (e.g., perforin production). A small proportion (approximately 6%), however, maintain phenotypic and functional T(CM) properties over a long time interval. These results suggest that T(EM) cells provide immediate effector function by a fraction of cells as well as self-renewal by others through up-regulation of CCR7 followed by either secondary peripheral effector function or long term maintenance of T(CM)-like properties.

We showed previously that mice with an inactivating knockin mutation in the p110delta isoform of PI3K (referred to as p110delta(D910A) mice) displayed enhanced primary resistance to Leishmania major despite mounting paradoxically impaired T cell responses. In this study, we show that p110delta(D910A) mice are impaired in their secondary (memory) anti-Leishmania responses in vitro and in vivo. Following secondary L. major challenge, p110delta(D910A) mice exhibited reduced delayed-type hypersensitivity response and weaker parasite control compared to wild-type mice. Using adoptive transfer experiments, we show that immune T cells from healed p110delta(D910A) mice were impaired in their proliferation and effector cytokine (IFN-gamma) responses upon L. major challenge. Interestingly, Leishmania-reactive T cells from healed p110delta(D910A) mice contain severalfold lower numbers of CD62L(lo) and CD62(hi) T cells than those from healed wild-type mice. The reduction in numbers of CD62L(lo) T cells in p110delta(D910A) mice is due to failure of their CD62L(hi) T cells to downregulate CD62L expression in response to L. major. Furthermore, although CD62L(lo) cells from p110delta(D910A) mice could home efficiently to lymphoid organs, their ability to exit these tissues and emigrate to cutaneous sites of infection was greatly impaired. Collectively, our data identify PI3K signaling as important events that control memory T cell subset differentiation, generation, effector function, and recruitment to cutaneous tissues and suggest that manipulating this pathway could provide means of enhancing desired memory T cell subset, response during vaccination, or both.

Chronic venous disease with skin changes of the leg is a common condition affecting up to 1 in 20 people in westernized countries. The causes of this problem are not fully understood, although research in recent years has revealed a number of important mechanisms that contribute to the disease process. Patients with chronic venous disease suffer persistently raised pressures in their deep and superficial veins in the lower limb. Leucocytes become "trapped" in the circulation of the leg during periods of venous hyper-tension produced by sitting or standing. Studies of the plasma levels of neutrophil granule enzymes shows that these are increased during periods of venous hypertension, suggesting that this causes activation of the neutrophils. Investigation of the leucocyte surface ligands CD11b and CD62L shows that the more activated neutrophils and monocytes are sequestered during venous hypertension. Measurement of plasma levels of the soluble parts of the endothelial adhesion molecules VCAM, ICAM, and ELAM show that these are all elevated in patients with chronic venous disease compared to controls. Following 30 minutes of venous hypertension produced by standing, these levels are further increased. These data suggest that venous hypertension causes neutrophil and monocyte activation, which in turn causes injury to the endothelium. Chronic injury to the endothelium leads to a chronic inflammatory condition of the skin that we know clinically as lipodermatosclerosis. This is mediated by perivascular inflammatory cells, principally macrophages, in the skin microcirculation. These stimulate fibroblasts in the skin leading to tissue remodeling and laying down of fibrous tissue. Vascular endothelial growth factor stimulates proliferation of capillaries within the skin. Skin in this state has the potential to ulcerate in response to minor injury.

This study demonstrates, for the first time, that murine regulatory T (Treg) cells in the tumor microenvironment display both enhanced proliferation and reduced functionality. This enhanced proliferation, combined with decreased apoptosis, leads to an intratumoral accumulation of Treg cells with a unique phenotype: CD4(+)CD25(+)FoxP3(+)GITR(high)CD27(low)CD62L(-). The loss of functionality is associated with down-regulation of the TCR signaling complex, including IL-2-inducible T cell kinase. It is also demonstrated that tumor-infiltrating Treg cells have impaired TCR-mediated signaling and calcium influx. Based on these findings, this study supports the hypothesis that 1) tumor-infiltrating Treg cells lose functionality due to their diminished ability to become effectively activated and 2) intratumoral accumulation of Treg cells may compensate for the impaired functionality, thus maintaining immune tolerance to the tumor.

Establishing reliable phenotypic data sets from the analysis of peripheral blood lymphocytes of normal animals is required to assess disease states. The rhesus macaque animal model is well established with respect to adult animals, but limited data are available that characterizes lymphocyte subsets in normal neonates. To address this, we used four-color flow cytometric analysis to follow phenotypic changes in 29 normal rhesus animals through their first ten months of life. From birth to 44 wk of age, the white cell count and absolute lymphocyte count were both elevated compared to adults. CD4+ cells constituted over 80% of all T cells at birth, a percentage that declined gradually over the first 12 wk of life, coincidental with increases in the percentages of CD8+ T cells, CD3-8+ natural killer cells and CD20+ B cells. This difference in relative frequency of CD4 and CD8 results in a significant skewing of CD4:CD8 ratio from 0.7:1 in adults to 3.5:1 in neonates. In addition, the predominant population of T lymphocytes consisted of CD45RA+CD62L+ naive cells. This subset continues to be the predominant phenotype for at least the first year of age. After birth the expression of activation markers (CD25) increased particularly on CD4+ T cells, although these levels generally reached a frequency similar to that observed in adults between 12 and 20 weeks after birth. These results are similar to those seen in humans and further confirm the reliability of the rhesus macaque animal model to study human diseases.

The ability of environmental contaminant trichloroethylene to alter immune function and promote autoimmunity was tested in female MRL(+/+) mice. MRL(+/+) mice exposed to occupationally relevant doses of trichloroethylene in their drinking water for 32 weeks developed autoantibodies and pathological evidence of autoimmune hepatitis. The ability of trichloroethylene (TCE) to promote autoimmunity was associated with the expansion of activated (CD44(hi) CD62L(lo)) CD4(+) T-lymphocytes that produced increased levels of the pro-inflammatory cytokine interferon (IFN)-gamma. Activated T-lymphocytes can accumulate if activation-induced apoptosis is suppressed. Consequently, the effect of TCE on apoptosis in CD4(+) T-lymphocytes was investigated. These experiments were conducted with TCE and one of the major oxidative metabolites of trichloroethylene, namely trichloroacetaldehyde hydrate (TCAH). CD4(+) T-lymphocytes isolated from MRL(+/+) mice exposed to TCE or TCAH in their drinking water for 4 weeks were resistant to activation-induced apoptosis in vitro. The TCE-or TCAH-induced decrease in activation-induced apoptosis was associated with decreased expression of FasL, one of the cell surface molecules that mediate apoptosis. These results suggest that exposure to the common water contaminant TCE or its metabolite TCAH inhibits activation-induced apoptosis in CD4+ T-lymphocytes, thereby promoting autoimmune disease by suppressing the process that would otherwise delete activated self-reactive T-lymphocytes.

Management of yellow fever is focused on the prevention of illness by the use of the yellow fever virus (YFV) 17D vaccine. The role of neutralizing antibodies in protection is generally accepted with YFV-specific T cells likely contributing to the control of viral replication. We studied CD8(+) T-cell responses to four defined human leucocyte antigen-B35-restricted epitopes in YFV vaccine recipients as a model of the kinetics of cytotoxic T-lymphocyte responses to an acute human viral infection. Multiple features of these epitope-specific responses were analysed after vaccination including magnitude, cytokine production, phenotype and T-cell receptor repertoire. Peak peptide-specific interferon-gamma (IFN-gamma) responses of almost 1% of CD8(+) T cells were seen as early as 2 weeks post-vaccination; however, dominant responses varied between donors. Peptide-specific responses were still detectable at 54 months post-vaccination. Tetramer-positive cells, at high frequencies, were detected as early as 7-9 days, before detectable IFN-gamma-producing cells, suggesting a defect in the functional capacity of some antigen-specific cells early post-vaccination. The predominant memory phenotype of the tetramer-positive population was a differentiated effector (CD45RA(+) CCR7(-) CD62L(-)) phenotype. The T-cell receptor Vbeta analysis revealed a diverse oligoclonal repertoire in tetramer-positive T-cell populations in two individuals. These characteristics of the YFV-specific T-cell response could contribute to vaccine effectiveness.

The adhesion molecule L-selectin is cleaved rapidly from the surface of activated leukocytes by tumor necrosis factor-alpha converting enzyme, a cell surface metalloprotease, and also undergoes slower constitutive shedding in unactivated cells. The structural features that render it susceptible to shedding are poorly understood. We therefore analyzed the shedding of a series of mutant and chimeric L-selectin molecules. Although murine L-selectin is cleaved at a specific location in the juxtamembrane region 11 amino acids distal to the cell membrane, this cleavage has little sequence specificity. However, proline substitution at the P2' or P3' position or deletion of the epidermal growth factor (EGF) domain completely blocks the rapid phorbol ester-induced cleavage, but does not affect the slower basal proteolytic shedding. Insertion of the 15-residue membrane-proximal region (MPR) of L-selectin into the heterologous protein B7.2 results in a molecule that undergoes constitutive proteolytic turnover. In contrast, insertion of both the EGF domain and the MPR confers susceptibility to both slow constitutive shedding and the rapid proteolytic cleavage induced by phorbol 12-myristate 13-acetate. These results demonstrate that constitutive and induced L-selectin cleavage are separable processes and that the rapid phorbol ester-induced shedding requires the presence of the EGF domain, a sequence that is remote from the cleavage site.

Monocytes constitutively migrate from the bloodstream across the vascular endothelium for systemic immune surveillance and maintenance of macrophage populations. They also perform reverse transendothelial migration (TEM) across the endothelium, which is required for entry of tissue monocytes/macrophages into the lymphatics or back into the bloodstream. We have modeled these processes previously using HUVEC monolayers grown on three-dimensional collagen matrices. The aim of the present study was to determine whether HIV-1 infection of monocytes/macrophages in vitro affects TEM. Purified primary human monocytes and monocyte-derived macrophages (MDM) expressed important TEM proteins such as CD62L, CD18, PECAM-1, CCR2, and CCR8. Purified monocytes underwent efficient forward and reverse TEM across HUVEC, and this function was maintained by MDM after up to 15 days of culture. Monocytes exposed to HIV-1 for 2 days had unaltered forward or reverse TEM. However, HIV-1 infection of MDM for 7 days decreased reverse TEM by an average of 66.5% compared with mock-infected MDM (n=9 independent donors; P=0.004), without affecting forward TEM. Decreased reverse TEM by HIV-infected MDM required viral RT and was not a result of alterations in surface expression of CCR8 or p-glycoprotein or a general impairment in mobility, as assessed by migration toward fMLP. This study indicates that HIV-1 infection of macrophages reduces their capacity to emigrate from the subendothelial extracellular matrix in vitro, which could result in defective cell-mediated immune responses to infections and promote establishment of viral reservoirs of HIV in tissue macrophages in vivo.

CD160 is an Ig-like glycoprotein expressed on NK, NKT and TCRgammadelta T cells, as well as intestinal intraepithelial T lymphocytes. In addition, a minor subset of CD8(+) but not CD4(+) T cells in the periphery is also known to express CD160, but the subset has not been fully characterized. In this study, we prepared anti-murine CD160 mAbs and investigated the expression profile of CD160 on various subsets of CD8(+) T cells. The amount of CD160 on almost all CD8(+) T cells was increased upon CD3-mediated stimulation in vitro, and soluble CD160 was found to be released. Flow cytometric analysis revealed most CD8(+) T cells expressing CD160 to show a CD44(high) phenotype in vivo. On further analysis, both CD44(high)CD62L(low) effector memory T cells (T(EM)) and CD44(high)CD62L(high) central memory T cells (T(CM)) expressed CD160 at an intermediate level. High levels were evident with recently activated CD8(+) T(EM). Naïve CD8(+) T cells presumably immediately after stimulation (CD44(low)CD62L(low)CD69(+)) also expressed CD160, but only at a low level. Purified CD160(+) CD8(+) T cells from OT-1 transgenic mice expressing TCR against OVA residues 257-264 presented by H-2K(b) produced IFN-gamma more rapidly than CD160(-) CD8(+) T cells upon antigen stimulation. These results together show that CD160 is expressed on the majority of CD8(+) memory T cells as well as recently activated CD8(+) T cells.

To determine whether the thymus is still functional despite age-related involution, we measured a biomarker for thymopoiesis known as the T cell receptor excision circle (TREC) from peripheral blood mononuclear cells (PBMCs) of 148 healthy children and from PBMCs, CD4(+), and CD8(+) cells of 32, 30, and 50 healthy adults, respectively. We demonstrate that during the first 5 years of life, thymic output is decreased (P 0.002) but not dramatically (r = -0. 282). Among adults aged 23-58, thymic output was inversely correlated with age, as measured from PBMCs (r = -0.628, P < 0.0005), CD4(+) (r = -0.530, P 0.003), and CD8(+) fractions (r = -0.385, P 0. 006). A strong correlation existed between pediatric PBMC TRECs and the expression of three naïve phenotypic markers (CD45RA(+)CD45RO(-), CD45RA(+)CD62L(+), and CD45RO(-)CD27(+)CD95(low)). Adult PBMC TRECs correlated only with the expression of CD45RA(+)CD45RO(-) (r = 0.459, P 0.012). Our data suggest that in adults CD45RA(+)CD45RO(-) may be enriched for TRECs and add to a growing body of evidence illustrating intact thymic function in adulthood.

MicroRNA (miR)-17-92a expression plays a crucial role in lymphocyte ontogeny. We therefore set out to determine miR-92a expression levels in peripheral blood lymphocytes from healthy subjects to ascertain any association between these levels and ageing. We found a positive correlation between the miR-92a expression level and the percentages of RO-CD8+CD27+ (P = 0.0046) and CD3+CD8+CD62L+ (P = 0.0011). This suggests that the majority of miR-92a of CD8+ T cells is derived from naïve cells, and the miR-92a expression level in CD8+ T cells declines progressively with age. These results indicate that the age-related attrition of naïve T cells is linked to a reduction of miR-92a in human T -lymphocytes. Therefore, we should careful attention when evaluating human miRNA levels in T lymphocytes to use normal control values.

BACKGROUND

The major aim of this study was to quantify long-term changes in bone marrow-derived cell populations after exposure to radiations of differing quality.

METHODS

Mice were whole-body irradiated to 2 Gy gamma, proton, carbon or iron radiation, and euthanized approximately 110 days later for immunocyte phenotyping.

RESULTS

Splenic lymphocytes and mono/macrophages increased after gamma-rays when compared to 0 Gy and one or more of the other groups. There were high T cells (carbon vs. 0 Gy), high B cells (gamma-rays vs. 0 Gy), and low natural killer (NK) cells (proton and carbon vs. 0 Gy). All radiations, except gamma-rays, increased CD62L+ memory T cell counts, whereas CD62L+ B cells increased only after gamma-rays.

CONCLUSIONS

There were significant aberrations in many immune parameters nearly 4 months after exposure to various forms of radiation. This suggests radiation exposure can have long-term health consequences.

BACKGROUND

The mechanism of CD4 T-cell decline in HIV-1 infection is unclear, but the association with plasma viral RNA load suggests viral replication is involved. Indeed, viremic controller patients with low viral RNA loads typically maintain high CD4 T-cell counts. Within a local cohort of 86 viremic controllers, we identify a subgroup (18 "discord controllers") with low CD4 T-cell counts that present clinical uncertainty. The underlying mechanism accounting for CD4 T-cell decline in the face of low or undetectable plasma (RNA) viral load remains unresolved. The objective of this study was to investigate the viral and host immune system dynamics in discord controllers by measuring cellular HIV-1 DNA load, T-cell populations, and T-cell activation markers.

METHODS

We compared discord controllers (viral RNA load <2000 copies/mL, <450 CD4 T-cells/mm) with typical controllers (viral RNA load <2000 copies/mL, >450 CD4 T-cells/mm) and progressors (viral RNA load >10,000 copies/mL, <450 CD4 T-cells/mm). We quantified CD4/CD8 naive/central memory/effector memory subsets (CD45RA/RO ± CD62L), activation levels (CD38HLA-DR), and HIV-1 DNA load.

RESULTS

Discord controllers resembled progressors showing high viral DNA load, depletion of naive CD4 T-cells, and higher activation in all CD4 T-cell subsets, compared with typical controllers. They were similar to typical controllers with lower CD8 T-cell activation compared with progressors.

CONCLUSIONS

Our data are consistent with a relationship between CD4 T-cell activation and disease progression. HIV-1 DNA load may be a better marker of viral replication and disease progression than viral RNA load. Lower level CD8 T-cell activation correlates with low viral RNA load but not with disease progression or viral DNA load.