Gammaherpesviruses can persist in the host in the face of an aggressive immune response. T cells recognize Ags expressed in both the productive and latent phases of the virus life cycle, however little is known about their relative roles in the long-term control of the infection. In this study we used the murine gammaherpesvirus 68 model system to investigate the relative properties of CD8 T cells recognizing lytic and latent viral Ags. We report that the CD8 T cell response to lytic phase epitopes is maximal in the lungs of infected mice at approximately 10 days postinfection, and is of progressively lesser magnitude in the mediastinal lymph nodes and spleen. In contrast, the CD8 T cell response to the latent M2 protein is maximal at approximately 19 days postinfection and is most prominent in the spleen, then progressively less in the mediastinal lymph node and the lung. Latent and lytic Ag-specific CD8 T cells had markedly different cell surface phenotypes during chronic infection, with latent Ag-specific cells being predominantly CD62L(high) or CD43 (1B11)(high). Lytic Ag-specific T cells had significantly lower expression of these markers. Importantly, latent but not lytic Ag-specific T cells could kill target cells rapidly in vivo during the chronic infection. These two different sets of CD8 T cells also responded differentially to IL-7, a cytokine involved in T cell homeostasis and the maintenance of T cell memory. These data have important implications for our understanding of immunological control during chronic gammaherpesvirus infections.

OBJECTIVE

The proinflammatory cytokine interleukin (IL)-6 is involved in various chronic inflammatory processes. IL-6 is a predominant cytokine produced by lamina propria T cells in Crohn's disease and experimental colitis. This study was designed to examine the effect of a neutralizing IL-6-receptor (IL-6R) antibody on the programmed cell death of mucosal T cells in the CD62L+ CD4+ SCID transfer model of chronic experimental colitis in mice and to gain more insight into the pathogenesis of this transfer colitis model.

METHODS

For adoptive transfer, we isolated CD62L+ CD4+ double-positive T cells from wild-type BALB/c mice followed by intraperitoneal application of 1 million cells in CB17 SCID mice. The purity of the transferred T-cell population was tested by FACS analysis. Cytokine secretion was measured by ELISA. Western blot analysis was performed to detect phospho-STAT-3 in protein extracts of splenic cells. Cryo- and paraffin colon cross-sections were used to perform immunochemical or fluorescence TUNEL stainings.

RESULTS

We isolated CD62L+ CD4+ and CD62L- CD4+ T cells. In vitro studies showed an increased production of IL-4 by CD62L- CD4+ T cells compared to CD62L+ T cells. 8-10 weeks after transfer of CD62L+ CD4+ T cells in SCID mice, reconstituted mice developed wasting disease, anal prolapse and diarrhea, whereas mice reconstituted with CD62L- CD4+ did not, similar to anti-IL-6R-treated CD62L+ CD4+-reconstituted SCID mice. Anti-IL-6R-treated reconstituted SCID mice showed decreased levels of activated STAT-3. The previously described efficacy of anti-IL-6R antibody treatment on colitis activity appeared to be due to the induction of apoptosis, as many TUNEL-positive cells were detected in the lamina propria.

CONCLUSIONS

These results suggest that the activation of the IL-6/STAT-3-signaling pathway plays a pivotal role in the pathogenesis of CD62L+ CD4+ transfer colitis. Moreover, the application of a neutralizing antibody to IL-6R induces apoptosis in transferred T cells. These data implicate the importance of anti-apoptotic pathways in chronic disease and might contribute to future therapies.

The voltage-gated potassium channel Kv1.3 has been recently identified as a molecular target that allows the selective pharmacological suppression of effector memory T cells (T(EM)) without affecting the function of naïve T cells (T(N)) and central memory T cells (T(CM)). We found that Kv1.3 was expressed on glomeruli and some tubules in rats with anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). A flow cytometry analysis using kidney cells revealed that most of the CD4(+) T cells and some of the CD8(+) T cells had the T(EM) phenotype (CD45RC(-)CD62L(-)). Double immunofluorescence staining using mononuclear cell suspensions isolated from anti-GBM GN kidney showed that Kv1.3 was expressed on T cells and some macrophages. We therefore investigated whether the Kv1.3 blocker Psora-4 can be used to treat anti-GBM GN. Rats that had been given an injection of rabbit anti-rat GBM antibody were also injected with Psora-4 or the vehicle intraperitoneally. Rats given Psora-4 showed less proteinuria and fewer crescentic glomeruli than rats given the vehicle. These results suggest that T(EM) and some macrophages expressing Kv1.3 channels play a critical role in the pathogenesis of crescentic GN and that Psora-4 will be useful for the treatment of rapidly progressive glomerulonephritis.

We identified functionally polarized subsets of CD4 memory T cells on the basis of the expression of CD11a, CD45RA and CD62L. Within the several phenotypically distinct subsets of CD4 memory cells are two that, upon stimulation, produce primarily IL-4 (MT(2), CD45RA(-)CD62L(+)CD11a(dim)) or primarily IFN-gamma (MT(1), CD45RA(-)CD62L(-)CD11a(bright)). In addition, four other phenotypically distinct subsets of CD4 cells have unique cytokine profiles. To determine the clinical relevance of the representation of these cell types, we analyzed blood from patients with the chronic diseases leprosy and atopy. These diseases are characterized as immunologically polarized, since T cell responses in affected individuals are often strongly biased towards T(h)1 (dominated by IFN-gamma production) or T(h)2 (IL-4 production). We show here that this polarization reflects homeostatic or differentiation mechanisms affecting the representation of the functionally distinct subsets of memory CD4 T cells, MT(1) and MT(2). Significantly, the representation of the MT(1) and MT(2) subsets differs dramatically between subjects with tuberculoid leprosy (a T(h)1 disease), or lepromatous leprosy or atopic disease (T(h)2 diseases). However, there was no difference in the cytokine profiles of these or any of the other finely resolved CD4 subsets, when compared between individuals across all disease states. Thus, it is the representation of these subsets in peripheral blood that is diagnostic of the polarized state of the immune system.

Mouse studies demonstrated that infusion of CD4+CD25+ regulatory T cells (Tregs) prevented graft versus host disease (GVHD) lethality after bone marrow transplantation (BMT). But the potential impact of human Tregs on GVHD has not been well demonstrated. In this study, we demonstrated that human Tregs enriched from peripheral blood of healthy donors could be expanded ex vivo to clinically relevant cell numbers in 2-3 weeks while maintaining Foxp3, CD25, CTLA-4, and CD62L expression as well as in vitro suppressive function. Furthermore, injection of human PBL into NOD/SCID mice induced lethal xenogenic GVHD, but co-transfer of expanded human Tregs with human PBL significantly enhanced survival, reduced GVHD symptoms, and inhibited human IgG/IgM production in the NOD/SCID mice. These results demonstrated that ex vivo expanded human Tregs retained their in vivo suppressive activity and prevented lethal xenogeneic GVHD, revealing the therapeutic potential of expanded human Tregs for GVHD.

OBJECTIVE

Compelling evidence implicates peripheral immune activation in the pathophysiology of preeclampsia. Polymorphonuclear neutrophils appear to be the cells most strongly affected, with changes in expression of surface markers and release of granule enzymes. Here, we investigated activation in additional leukocyte populations among women with preeclampsia.

METHODS

We used flow cytometry to evaluate changes in leukocyte markers in preeclampsia compared with uncomplicated pregnancy. To gain insights into intracellular pathways involved in leukocyte activation, we monitored the NF-kappaB signal transduction pathway. Plasma levels of interleukin-6 (IL-6) were also studied as an additional indication of cellular activation.

RESULTS

Preeclampsia is associated with changes in L-selectin (CD62L) on neutrophils (P = 0.004), monocytes (P = 0.013), and T cells (P = 0.048) when compared with normal pregnancy. These changes include an increase in nuclear translocation of NF-kappaB and increased levels of IL-6 (P = 0.005).

CONCLUSIONS

These findings are consistent with the presence of a generalized phenomenon of immune activation in preeclampsia.

BACKGROUND

Vitamin D receptor (VDR) deficiency contributes to the development of experimental inflammatory bowel disease (IBD) in several different models. T cells have been shown to express the VDR, and T cells are targets of vitamin D. In this article we determined the effects of VDR expression on CD8+ T cells.

RESULTS

VDR KO CD8+ T cells, but not WT CD8+ T cells, induced colitis in Rag KO recipients. In addition, co-transfer of VDR KO CD8+ T cells with naïve CD4+ T cells accelerated colitis development. The more severe colitis was associated with rapidly proliferating naïve VDR KO CD8+ T cells and increased IFN-γ and IL-17 in the gut. VDR KO CD8+ T cells proliferated in vitro without antigen stimulation and did not downregulate CD62L and upregulate CD44 markers following proliferation that normally occurred in WT CD8+ T cells. The increased proliferation of VDR KO CD8+ cells was due in part to the higher production and response of the VDR KO cells to IL-2.

CONCLUSIONS

Our data indicate that expression of the VDR is required to prevent replication of quiescent CD8+ T cells. The inability to signal through the VDR resulted in the generation of pathogenic CD8+ T cells from rapidly proliferating cells that contributed to the development of IBD.

BACKGROUND

Immunological and virological consequences of low-level viremia in human immunodeficiency virus (HIV) type 1-infected patients receiving highly active antiretroviral therapy (HAART) remain to be determined.

METHODS

For 24 months, 101 HAART-treated, HIV-1-infected patients with HIV RNA levels </=200 copies/mL were followed prospectively: HIV RNA level and CD4 and CD8 cell counts were investigated every 3 months, and proviral DNA and T cell subsets were investigated every 6 months.

RESULTS

During follow-up, 33 patients had HIV RNA levels </=20 copies/mL at all visits (uVL patients), whereas 68 patients had HIV RNA levels >20 copies/mL at>>/=1 visit (dVL patients) (median increase, 81 copies/mL [interquartile range, 37-480 copies/mL]). dVL patients had higher concentrations of CD8 cells, activated and memory T cells, and proviral DNA, compared with uVL patients (P<.05). A higher HIV RNA level was independently associated with reduced CD4 gain (P<.001). A higher HIV RNA level also was associated with increases in activated CD8(+)CD38(+) and CD8(+)HLA-DR(+) cells (P<.05), and a higher level of activated CD8(+)CD38(+) cells was independently associated with reduced CD4 gain (P<.05). A higher proviral DNA level was associated with increases in CD4(+)CD45RA(-)CD28(-) effector cells and reductions in naive CD4(+)CD45RA(+)<em>CD62L</em>(+) and CD8(+)CD45RA(+)<em>CD62L</em>(+) cells (P<.05). Higher levels of activated CD4(+)HLA-DR(+) and early differentiated CD4(+)CD45RA(-)CD28(+) cells predicted increased risk of subsequent detectable viremia in patients with undetectable HIV RNA (P<.05).

CONCLUSIONS

These findings indicate that low-level viremia and proviral DNA are intimately associated with the immunological and virological equilibrium in patients receiving HAART.

Although the effect of IL-15 has been described on murine cells in vitro and in vivo, its effect on human memory CD8(+) T cells is not well characterized. We show here that IL-15 preferentially enhances the activation and effector function of human effector-memory CD45RA(-)CD62L(-) and CD45RA(+)CD62L(-) CD4(+) and CD8(+) T cells in both healthy and HIV-infected individuals. We find that IL-15 increases 2- to 5-fold both the activation and secretion of the effector cytokines IFN-gamma and tumor necrosis factor (TNF)-alpha by anti-CD3-stimulated purified CD4(+) and CD8(+) T cells and peripheral blood mononuclear cells from healthy and HIV-infected individuals. Furthermore, IL-15 potently inhibits CD95/Fas-induced apoptosis of the effector-memory CD4(+) and CD8(+) T cells from HIV-infected individuals. These findings suggest that in addition to being a growth and survival factor for memory CD8(+) T cells, IL-15 is also a potent activator of human effector-memory CD8(+) T cells both in healthy and in HIV-infected individuals.

The aim of this study was to identify a novel immunological indicator useful for the early diagnosis (through a rapid and single determination) of neonatal sepsis (NS). Peripheral blood samples were taken from 63 neonates, who were classified into four groups: proven NS (n = 17); clinical NS (n = 14); disease without infection (n = 17); and healthy newborns (n = 15). Neutrophil expression of CD64, CD43, CD44, CD50, CD62L and Mac-1, and plasma levels of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha (TNF-alpha) and soluble L-selectin (sCD62L), were determined. Expression of CD64 was significantly enhanced in the group with proven sepsis and clinical NS compared to newborns without infection (p < 0.05). Eight newborns with proven or clinical sepsis, but only one with disease without infection, showed an increased percentage of CD64+ cells (diagnostic specificity = 96.8%). No significant differences were found in the expression of the other leucocyte differentiation antigens studied. As previously described, TNF-alpha and IL-6 levels were significantly elevated in newborns with proven or clinical sepsis compared to neonates without infection (p < 0.05). Our results suggest that, through a single determination, the enhanced expression of CD64 is a highly specific indicator of NS, although its diagnostic sensitivity is low (25.8%). In contrast, we found that plasma levels of IL-1beta and sCD62L, as well as the expression of Mac-1, CD43, CD44, CD50, and CD62L, do not appear to be useful for the diagnosis of NS.

Tumor necrosis factor (TNF) plays a pivotal role in the pathogenesis of Crohn's disease (CD). However, little is known about the role of TNF receptors (TNF-R) in this disease. Here, we found that TNF-R2 (in contrast to TNF-R1) was significantly up-regulated on lamina propria and peripheral blood T cells in CD compared to control patients. To directly test the functional role of TNF-R2 in Th1-mediated experimental colitis in vivo, we took advantage of transgenic animals overexpressing TNF-R2 in T cells. Reconstitution of SCID mice with CD4+ CD62L+ T cells from TNF-R2 transgenic mice led to an earlier wasting syndrome, a more severe colitis and augmented Th1 cytokine production than reconstitution with cells from wild-type littermates. In addition, TUNEL staining revealed a significantly decreased apoptosis rate of lamina propria mononuclear cells in mice reconstituted with TNF-R2 transgenic T cells compared to mice reconstituted with wild-type T cells. In summary, our data suggest a critical regulatory role of TNF-R2 signaling for disease exacerbation in Th1-mediated chronic colitis. Taken together with the increased expression of TNF-R2 in CD, selective targeting of TNF-R2 signaling thus emerges as a potentially novel approach to the treatment of CD.

Interactions of hematopoietic progenitor cells (HPC) with their local microenvironments in the bone marrow are thought to control homing, differentiation, and self-renewal of the cells. To dissect the role of extracellular matrix (ECM) components of the niche microenvironment, a set of well-defined ECM coatings including fibronectin, heparin, heparan sulphate, hyaluronic acid, tropocollagen I, and co-fibrils of collagen I with heparin or hyaluronic acid was prepared and analysed with respect to the attachment of human CD133+ HPC in vitro. The extension of the adhesion areas of individual cells as well as the fraction of adherent cells were assessed by reflection interference contrast microscopy (RICM). Intense cell-matrix interactions were found on surfaces coated with fibronectin, heparin, heparan sulphate, and on the collagen I based co-fibrils. Insignificant adhesion was found for tropocollagen I and hyaluronic acid. The strongest adhesion of HPC was observed on fibronectin with contact areas of about 7 microm(2). Interaction of HPC with coatings consisting of heparin, heparan sulphate, and co-fibrils result in small circular shaped contact zones of 3 microm(2) pointing to another, less efficient, adhesion mechanism. Analysing the specificity of cell-matrix interaction by antibody blocking experiments suggests an integrin(alpha(5)beta(1))-specific adhesion on fibronectin, while adhesion on heparin was shown to be mediated by selectins (CD62L). Taken together, our data provide a basis for the design of advanced culture carriers supporting site-specific proliferation or differentiation of HPC.

Developing thymocytes undergo maturation while migrating through the thymus and ultimately emigrate from the organ to populate peripheral lymphoid tissues. The process of thymic emigration is controlled in part via receptor-ligand interactions between the chemokine stromal-derived factor (SDF)-1, and its cognate receptor CXCR4, and sphingosine 1-phosphate (S1P) and its receptor S1PR. The precise mechanism by which S1P/S1PR and CXCR4/SDF-1 contribute to thymic emigration remains unclear. We proposed that S1P-dependent and -independent mechanisms might coexist and involve both S1P-induced chemoattraction and SDF-1-mediated chemorepulsion or fugetaxis of mature thymocytes. We examined thymocyte emigration in thymi from CXCR4-deficient C57BL/6 embryos in a modified assay, which allows the collection of CD62L(high) and CD69(low) recent thymic emigrants. We demonstrated that single-positive (SP) CD4 thymocytes, with the characteristics of recent thymic emigrants, failed to move away from CXCR4-deficient fetal thymus in vitro. We found that the defect in SP CD4 cell emigration that occurred in the absence of CXCR4 signaling was only partially overcome by the addition of the extrathymic chemoattractant S1P and was not associated with abnormalities in thymocyte maturation and proliferative capacity or integrin expression. Blockade of the CXCR4 receptor in normal thymocytes by AMD3100 led to the retention of mature T cells in the thymus in vitro and in vivo. The addition of extrathymic SDF-1 inhibited emigration of wild-type SP cells out of the thymus by nullifying the chemokine gradient. SDF-1 was also shown to elicit a CXCR4-dependent chemorepellent response from fetal SP thymocytes. These novel findings support the thesis that the CXCR4-mediated chemorepellent activity of intrathymic SDF-1 contributes to SP thymocyte egress from the fetal thymus.

Most HIV+ individuals require lifelong highly active antiretroviral therapy (HAART) to suppress HIV replication, but fail to eliminate the virus in part because of residual replication in gut-associated lymphoid tissues (GALT). Naturally elicited HIV-specific CD8+ T cells generated in the acute and chronic infectious phases exhibit antiviral activity, but decrease in number after HAART. Therapeutic vaccines represent a potential strategy to expand cellular responses, although previous efforts have been largely unsuccessful, conceivably because of a lack of responding HIV-specific central-memory CD8+ T cells (Tcm). To determine whether patients receiving HAART possess CD8+ T cells with Tcm qualities that are amenable to augmentation, HIV-specific CD8+ T-cell clones were derived from HIV-reactive CD28+CD8+ T-cell lines isolated from 7 HIV+ HAART-treated patients, expanded ex vivo, and reinfused into their autologous host. Tracking of the cells in vivo revealed that clones could persist for ≥ 84 days, maintain expression and/or re-express CD28, up-regulate CD62L, secrete IL-2, proliferate on cognate Ag encounter and localize to the rectal mucosa. These results suggest some infused cells exhibited phenotypic and functional characteristics shared with Tcm in vivo, and imply that more effective therapeutic vaccination strategies targeting CD8+ Tcm in patients on HAART might provide hosts with expanded, long-lasting immune responses not only systemically but also in GALT.

Dengue virus infection in the central nervous system (CNS) of immunized mice results in a strong influx of CD8 T cells into the brain. Whereas the kinetics of the splenic antiviral response are conventional, i.e. expansion followed by a rapid drop in the frequency of specific CD8 T cells, dengue virus-specific CD8 T cells are retained in the CNS at a high frequency. These CD8 T cells display a partially activated phenotype (CD69(high), Ly-6A/E(high), CD62L(low)), characteristic for effector-memory T cells. CD43 expression, visualized by staining with the 1B11 mAb, decreased in time, suggesting that these persisting CD8 T cells differentiated into memory cells. These data add to the growing evidence implicating the CNS as a non-lymphoid tissue capable of supporting prolonged T cell survival/maintenance.

Immunosuppression following severe sepsis remains a significant human health concern, as long-term morbidity and mortality rates of patients who have recovered from life-threatening septic shock remain poor. Mouse models of severe sepsis indicate this immunosuppression may be partly due to alterations in myeloid cell function; however, the effect of severe sepsis on subsequent CD4(+) T-cell responses remains unclear. In the present study, CD4(+) T cells from mice subjected to an experimental model of severe sepsis (cecal ligation and puncture (CLP)) were analyzed in vitro. CD4(+)CD62L(+) T cells from CLP mice exhibited reduced proliferative capacity and altered gene expression. Additionally, CD4(+)CD62L(+) T cells from CLP mice exhibit dysregulated cytokine production after in vitro skewing with exogenous cytokines, indicating a decreased capability of these cells to commit to either the T(H)1 or T(H)2 lineage. Repressive histone methylation marks were also evident at promoter regions for the T(H)1 cytokine IFN-gamma and the T(H)2 transcription factor GATA-3 in naïve CD4(+) T cells from CLP mice. These results provide evidence that CD4(+) T-cell subsets from post-septic mice exhibit defects in activation and effector function, possibly due to chromatin remodeling proximal to genes involved in cytokine production or gene transcription.

FTY720, a novel immunosuppressant, sequesters circulating mature lymphocytes, especially T cells, within lymph nodes and Peyer's patches by accelerating lymphocyte homing, and thereby causes lymphocyte depletion in the blood. The FTY720-induced acceleration of lymphocyte homing appears to be mediated by lymphocyte homing receptors including CD62L, CD49d/beta7, and CD11a/CD18. In this study, expressions of CD62L, CD49d and CD11a on T cells in the peripheral blood, lymph nodes and Peyer's patches were analysed by flow cytometry in rats given FTY720 (1 mg/kg) orally. FTY720 markedly decreased the number of peripheral blood T cells, while not affecting CD62L, CD49d and CD11a expressions at 1-3 hr after administration. In contrast, both the frequency of CD62L-positive T cells and intensity of CD62L expression on T cells were increased in Peyer's patches but not lymph nodes at 3 hr after administration of FTY720. CD49d and CD11a expressions on T cells were unaffected by FTY720 in both Peyer's patches and lymph nodes at the same point in time. On the other hand, analysis of lymphocyte homing with calcein-labelled lymphocytes and anti-CD62L monoclonal antibody (mAb) confirmed that FTY720 predominantly increased CD62L-dependent lymphocyte homing to Peyer's patches. These findings indicate that FTY720 increases the frequency of CD62L-positive T cells by accelerating CD62L-predominant homing in Peyer's patches.

Regulatory T cells (Tregs) play crucial roles in both fetal and tumor development. We recently showed that immunosurveillance by pre-existing CD44(high)CD62L(low) activated/memory Tregs (amTregs) specific for self-Ags protects emergent tumor cells in mice. This Treg response of a memory type is more rapid than and dominates the antitumor response of tumor-specific effector T cells. In this study, we report striking similarities between the early Treg responses to embryo and tumor implantation. Tregs are rapidly recruited to uterus-draining lymph nodes and activated in the first days after embryo implantation in both syngeneic and allogeneic matings; express the markers of the amTreg subset; and are at least in part self-Ag specific, as seen in tumor emergence. Unlike in the tumor emergence setting, however, for which preimmunization against tumor Ags is sufficient for complete tumor eradication even in the presence of Tregs, Treg depletion is additionally required for high frequencies of fetus loss after preimmunization against paternal tissue Ags. Thus, amTregs play a major role in protecting embryos in both naive and preimmune settings. This role and the ensuing therapeutic potential are further highlighted by showing that Treg stimulation, directly by low-dose IL-2 or indirectly by Fms-related tyrosine kinase 3 ligand, led to normal pregnancy rates in a spontaneous abortion-prone model.

Antiretroviral therapy commenced during primary human immunodeficiency virus type 1 (HIV-1) infection (PHI) may limit the extent of viral replication and prevent early loss of HIV-specific CD4 lymphocyte function. We studied the effect of current standard therapy (2 nucleoside analogues and a protease inhibitor) in 16 patients with symptomatic PHI. In the 13 patients who completed 1 year of treatment, plasma HIV RNA was <50 copies/mL and median CD4 cell counts were comparable to HIV-uninfected controls, with naive (CD45RA+CD62L+), primed (CD45RO+), and T cell receptor Vbeta subsets all within normal ranges. However, HIV-1 DNA levels in treated and untreated PHI patients were similar. Furthermore, CD8 cell counts remained elevated, including activated (CD38+HLA-DR+), replicating (Ki-67+), and cytotoxic (perforin+CD28-) lymphocytes. In conclusion, early antiretroviral therapy resulted in clearance of viremia and prevented loss of crucial CD4 subsets. The persistence of HIV-1 DNA together with increased CD8 T lymphocyte turnover and activation indicate continued expression of viral antigens.

OBJECTIVE

This study examined the effects of acute psychological stress and exhaustive exercise on the expression and density of adhesion molecules (L-selectin, lymphocyte function antigen-1 [LFA-1], and intracellular adhesion molecule-1 [ICAM-1]) on monocytes, granulocytes, and lymphocytes.

METHODS

Forty-five healthy volunteers performed a 15-minute public speaking task and a 15- to 18-minute bicycle ergometer challenge.

RESULTS

In general, both the exercise and speaking tasks led to increases in the number of circulating leukocytes and lymphocyte subsets. The density of L-selectin (CD62L) on mixed lymphocytes and T lymphocytes was decreased in response to exercise (p values < .001). Both stressors led to an increased density of LFA-1 (CD11a) on mixed lymphocytes (p values < .01), whereas CD11a density on monocytes and granulocytes remained unchanged. ICAM-1 (CD54) density was unaffected, but the number of lymphocytes, monocytes, and granulocytes expressing CD54 increased in the circulation on both stressors.

CONCLUSIONS

The data indicate that both psychological stress and exercise have significant effects on cellular expression of adhesion molecules on circulating leukocytes. Given the crucial role that adhesion molecules on circulating cells play in inflammation and disease, these findings may have clinical relevance in sympathetic nervous system-induced immune activation.

BACKGROUND

Recent studies have shown that neutrophils may display an antigen-presenting function and inhibit lymphocyte proliferation by expressing programmed cell death 1 ligand 1 (PD-L1). The current study was performed to investigate the effect of neutrophils and their pathophysiological significance during sepsis.

METHODS

Neutrophil PD-L1 expression was determined in both septic mice (n = 6) and patients (n = 41). Neutrophils from septic mice were subtyped into PD-L1 and PD-L1 populations to determine their phenotypes and functions. Septic neutrophils were cocultured with lymphocytes to observe the effect of septic neutrophils on lymphocyte apoptosis.

RESULTS

The PD-L1 level on neutrophils from septic mice was significantly up-regulated (21.41 ± 4.76%). This level increased with the progression of sepsis and the migration of neutrophils from the bone marrow to the blood and peritoneal cavity. The percentages of CD11a, CD62L, and C-C chemokine receptor type 2 were lower, whereas the percentages of CD16 and CD64 were higher on PD-L1 neutrophils than on PD-L1 neutrophils. The migratory capacity of PD-L1 neutrophils was compromised. Septic neutrophils induced lymphocyte apoptosis via a contact mechanism, and this process could be reversed by anti-PD-L1 antibody. PD-L1 was also up-regulated on neutrophils from patients with severe sepsis (14.6% [3.75%, 42.1%]). The levels were negatively correlated with the monocyte human leukocyte antigen-DR level and positively correlated with the severity of septic patients. Neutrophil PD-L1 was a predictor for the prognosis of severe sepsis, with an area of 0.74 under the receiver operating curve.

CONCLUSIONS

PD-L1 is up-regulated on neutrophils during sepsis, which may be related to sepsis-induced immunosuppression.

Neutrophils are essential effector cells in host defense against invading pathogens. Regulation of adhesion, migration, and chemotactic processes is important in the homing and activation of these cells. We recently described three distinct subsets of circulating human neutrophils in peripheral blood during acute systemic inflammation. One subset, CD16(bright)/CD62L(dim), has immune suppressive characteristics because it can inhibit T-cell proliferation. The other two subsets consist of banded CD16(dim)/CD62L(bright) and phenotypically mature (normal) CD16(bright)/CD62L(bright) neutrophils. The current study was designed to determine the adhesion characteristics of these different neutrophil subsets. Analysis of adhesion to activated endothelium under flow conditions revealed that CD16(bright)/CD62L(dim) neutrophils adhered less compared with CD16(bright)/CD62L(bright) and CD16(dim)/CD62L(bright) neutrophils. This decrease in binding capacity could be mimicked in the other neutrophil subsets by blocking L-selectin. Chemotaxis of CD16(bright)/CD62L(dim) neutrophils to the end-target chemoattractant N-formylmethionine-leucine-phenylalanine was lower compared with that for the CD16(dim)/CD62L(bright) neutrophil subset, whereas chemotaxis to cell-derived chemoattractant CXCL8 was comparable. Our data indicate that capture on endothelium under flow conditions, a key mechanism necessary for extravasation, of CD16(bright)/CD62L(dim) neutrophils to inflammatory sites is attenuated, which may facilitate migration of these cells to other tissue localizations. Modulation of this process is a potential target to manipulate inflammation because potentiation of this immune suppression might aid in anti-inflammatory therapy.

During the antigen-dependant activation process several subsets CD8+ T cells appear with different phenotypic and functional characteristics. Recent studies indicate that the state of T cell differentiation radically affects their ability to effectively respond to tumor challenge, with early effector CD8+ T (CD62Lhigh) cells having better anti-tumor activity. Thus strategies aimed at optimizing the generation of such subpopulations could significantly enhance the effectiveness of adoptive cell therapy (ACT) for cancer. In this study, we show that priming of naïve CD8+ T cells in the presence of IL-12 selectively rescued early CD8+ CD62L(hi) from activation induced cell death and resulted in the increased accumulation of this subset of CD8+ T cells. Furthermore, we demonstrated that IL-12 directly modulated the expression of CD62L on activated CD8+ T cells. When used for ACT, naïve CD8+ T cells primed in vitro in the presence of IL-12 showed superior anti-tumor activity toward B16 melanoma. Importantly, using the Pmel-1 model, priming pmel-1 cells in vitro with IL-12 reduced the state of functional tolerance associated with the non-mutated "self" tumor antigen gp100, as demonstrated by significant tumor responses in the absence of vaccination. Together, our results suggest that in vitro conditioning of naïve CD8+ T cells with IL-12 prior to ACT could significantly enhance their anti-tumor activity.

Adoptive T-cell transfer has achieved significant clinical success in advanced melanoma. However, therapeutic efficacy is limited by poor T-cell survival after adoptive transfer and by inefficient trafficking to tumor sites. Here, we report that intratumoral expression of the chemokine CCL21 enhances the efficacy of adoptive T-cell therapy in a mouse model of melanoma. Based on our novel observation that CCL21 is highly chemotactic for activated OT-1 T cells in vitro and down-regulates expression of CD62L, we hypothesized that tumor cell-mediated expression of this chemokine might recruit, and retain, adoptively transferred T cells to the sites of tumor growth. Mice bearing metastatic tumors stably transduced with CCL21 survived significantly longer following adoptive T-cell transfer than mice bearing non-CCL21-expressing tumors. However, although we could not detect increased trafficking of the adoptively transferred T cells to tumors, tumor-expressed CCL21 promoted the survival and cytotoxic activity of the adoptively transferred T cells and led to the priming of antitumor immunity following T-cell transfer. To translate these observations into a protocol of real clinical usefulness, we showed that adsorption of a retrovirus encoding CCL21 to OT-1 T cells before adoptive transfer increased the therapeutic efficacy of a subsequently administered dose of OT-1 T cells, resulting in cure of metastatic disease and the generation of immunologic memory in the majority of treated mice. These studies indicate a promising role for CCL21 in enhancing the therapeutic efficacy of adoptive T-cell therapy.