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Vgamma9Vdelta2 T lymphocytes recognize nonpeptidic Ags and mount effector functions in cellular immune responses against microorganisms and tumors, but little is known about their role in Ab-mediated immune responses. We show here that expression of CXCR5 identifies a unique subset of Vgamma9Vdelta2 T cells which express the costimulatory molecules ICOS and CD40L, secrete IL-2, IL-4, and IL-10 and help B cells for Ab production. These properties portray CXCR5+ Vgamma9Vdelta2 T cells as a distinct memory T cell subset with B cell helper function.

We have compared four human subsets of Vgamma9Vdelta2 T cells, naive (T(naive), CD45RA(+)CD27(+)), central memory (T(CM), CD45RA(-)CD27(+)), effector memory (T(EM), CD45RA(-)CD27(-)) and terminally differentiated (T(EMRA), CD45RA(+)CD27(-)), for their capacity to proliferate and differentiate in response to antigen or homeostatic cytokines. Cytokine responsiveness and IL-15R expression were low in T(naive) cells and progressively increased from T(CM) to T(EM) and T(EMRA) cells. In contrast, the capacity to expand in response to antigen or cytokine stimulation showed a reciprocal pattern and was associated with resistance to cell death and Bcl-2 expression. Whereas antigen-stimulated cells acquired a T(CM) or T(EM) phenotype, IL-15-stimulated cells maintained their phenotype, with the exception of T(CM) cells, which expressed CD27 and CD45RA in various combinations. These results, together with ex vivo bromodeoxyuridine incorporation experiments, show that human Vgamma9Vdelta2 memory T cells have different proliferation and differentiation potentials in vitro and in vivo and that T(EMRA) cells are generated from the T(CM) subset upon homeostatic proliferation in the absence of antigen.

The liver has specific mechanisms to protect itself from infectious agents and to avoid autoimmunity, indicating an important role of the hepatic tissues in antigen presentation and tolerance induction. Since intrahepatic lymphocytes may contribute to the innate immunity and to the liver pathology, it is of interest to analyze the expression of antigen presenting molecules and of the related T cell recognition in liver, and how these change in relation to different diseases. We analyzed the expression of MHC class I, and of CD1-a, -b, -c, and -d proteins on liver tissues from patients with different hepatic diseases. Moreover, in the same patients we studied the intrahepatic and peripheral NKT cell recognition of alpha-galactosyl ceramide antigen in the context of CD1d. Unlike in other tissues, classical MHC class I molecules were poorly expressed in the hepatic compartment, suggesting that inflamed hepatocytes may trigger weak MHC-restricted T cell responses. Nevertheless, we observed a prevalent expression of HLA class I-like CD1d isoform on the hepatocyte surface, indicating that CD1d is the main restriction element in the liver. In patients with viral hepatitis, the intrahepatic CD1d expression parallels the recruitment of CD56+Valpha24Vbeta11+ NKT cells in the liver which recognize CD1d presenting glycolipids such as alpha-galactosyl ceramide, suggesting that the intrahepatic T cell immunity may focus on glycolipid antigens.

Objective: The aim of this study was to develop a computational model of HIV infection able to simulate the natural history of the disease and to test predictive parameters of disease progression. Design: We describe the results of a numerical simulation of the cellular and humoral immune response to the HIV-1 infection as an adaptive pathway in a “bit-string” space. Methods: A total of 650 simulations of the HIV-1 dynamics were performed with a modified version of the Celada-Seiden immune system model . Results: Statistics are in agreement with epidemiological studies showing a lognormal distribution for the time span between the infection and AIDS development. As predictive parameters of disease progression we found that HIV-1 accumulates “bit”-mutations mainly in the peptide sequences recognized by cytotoxic CD8 T cells, indicating that cell-mediated immunity plays a major role in viral control. The viral load set-point was closely correlated with the time from the infection to AIDS development. Viral divergence from the viral quasispecies that was present at the beginning of the infection in long-term non-progressors (LTNP) was found to be similar to that found in rapid progressors at the time CD4 T cells drop below the critical value of 200 cells per ml. In contrast, the diversity indicated by the number of HIV strains present at the same time was higher for rapid and normal progressors compared to LTNP, suggesting that the early immune response can make the difference. Conclusion: This computational model may help to define the predictive parameters of HIV dynamics and disease progression, with potential applications in therapeutic and vaccines simulations.

Vdelta2 T lymphocytes recognize nonpeptidic antigens without presentation by MHC molecules and mount both immediate effector functions and memory responses after microbial infection. However, how Vdelta2 T cells mediate different facets of a memory response remains unknown. Here, we show that the expression of CD45RA and CD27 antigens defines four subsets of human Vdelta2 T cells with distinctive compartmentalization routes. Naive CD45RA+CD27+ and memory CD45RA-CD27+ cells express lymph node homing receptors, abound in lymph nodes, and lack immediate effector functions. Conversely, memory CD45RA-CD27- and terminally differentiated CD45RA+CD27- cells, which express receptors for homing to inflamed tissues, are poorly represented in the lymph nodes while abounding at sites of inflammation, and display immediate effector functions. These observations and additional in vitro experiments indicate a lineage differentiation pattern for human Vdelta2 T cells that generates naive cells circulating in lymph nodes, effector/memory cells patrolling the blood, and terminally differentiated effector cells residing in inflamed tissues.

BACKGROUND: Human immunodeficiency virus (HIV)- specific CD8-positive cytotoxic T-lymphocytes (CTL) play a key role in controlling HIV infection. Monitoring CTL response could be clinically relevant during structured therapy interruption (STI), HIV exposure, and vaccine trials. However, HLA patients' restriction and HIV variability limited the development of a CTL assay with broad specificity. MATERIALS AND METHODS: We designed an HLA-class I/HIV-1 clade independent assay for assessing HIV- specific CTL by using a computer-assisted selection ofthe CTL epitopes. Twenty-eight 15-mers were selected by peptide-binding motifs analysis using different databases (HIV-Immunology Database, SYFPEITHI, BIMAS). Altogether they putatively bind to more than 90% of HLA haplotypes in different populations, with an overall HIV-1 variability below 9%. The peptide pool was used as an antigen in an intracellular cytokine staining (ICS) assay for quantifying HIV-specific CTL response. RESULTS: The test can be performed using both fresh and cryopreserved peripheral blood mononuclear cells (PBMC), whereas GAG protein as antigen works only on fresh PBMC. A significantly higher CTL response with respect to HIV-negative controls was detected in all HIV-1 infected subjects of two groups of patients with different ethnicities (Caucasians and Africans) and coming from areas with different HIV-1 clade prevalences (clade B and A/G, respectively). In Caucasian patients, after month of STI, the number of HIV-1 specific CTL (2,896 +/- 2,780 IFN-gamma specific CD8 cells/ml) was significantly higher than that found at enrolment (2,125 +/- 4,426 IFN-gamma specific CD8 cells/ml, p< 0.05). CONCLUSIONS: These data indicate that this CTL assay is broadly specific and could represent a useful clinical tool for HIV immunodiagnostic independent of HLA-haplotype and HIV-clade variabilities.

BACKGROUND: Hepatitis C infection induces an acute and chronic liver inflammation that may lead to cirrhosis, liver failure, or hepatocarcinoma. Since the role of alphabeta T lymphocytes in hepatitis C virus (HCV) immunopathology has been analyzed extensively, we investigated the distribution and functional activation of gammadelta T cell subsets in chronically HCV-infected patients. MATERIALS AND METHODS: Blood samples and liver biopsies from 35 patients with compensated chronic HCV infection were compared in terms of T cell subset distribution, expression of activation markers, gammadelta T cell receptor (TCR) repertoire, and pattern of cytokine production. Moreover, we analyzed whether these immunological parameters were associated with other clinical observations (plasma viremia, ALT levels, Ishak index). RESULTS: Differing from peripheral blood distribution, a specific compartmentalization of Vdelta1 T cells (p < 0.001) was observed in the liver of HCV patients. These cells represented a relevant fraction of intrahepatic T lymphocytes (1.8-8.7%) and expressed the memory/effector phenotype (CD62-L- CD45-RO+CD95+). This phenotype was consistent with selective homing upon antigen recognition. Mitogenic stimulation of Vdelta1 + T lymphocytes recruited in the liver revealed the T helper cell type 1 (Th1) pattern of cytokine secretion. Interestingly, the frequency of interferon-gamma (IFN-gamma)-producing Vdelta1 T cells was associated with an higher degree of liver necroinflammation, measured by the Ishak index. Finally, the T-cell repertoire analysis revealed the absence of Vgamma selection in the TCR repertoire of intrahepatic Vdelta1 T cells. CONCLUSIONS: gammadelta T cell distribution in the peripheral blood differs from the Vdelta1 T cell subset because it is policlonally activated and recruited in the liver of chronic HCV-infected patients. During HCV-infection, this T cell subset may release Th1 cytokines and contribute to the necroinflammatory liver disease.

Human gammadelta T lymphocytes respond to viral, bacterial, protozoal, and tumoral antigens, but their precise function remains unknown. In adults the major circulating gammadelta T-cell subset expresses the Vgamma9Vdelta2 T-cell receptor and responds to protease-resistant phosphorylated derivatives found in many pathogens. In this study we show that activation of Vdelta2(+) cells with the nonpeptidic antigen isopentenyl pyrophosphate (IPP) rapidly induces (within 4-12 hours) the C-C chemokines MIP-1alpha, MIP-1beta, and lymphotactin but not MCP-1. The most robust response was obtained for MIP-1beta. IPP induction of MIP-1alpha and MIP-1beta was not affected by costimulation with interleukin-4 (IL-4), IL-10, TGF-beta, or interferon-gamma (INF-gamma). However, IL-12 significantly enhanced IPP-induced expression and release of MIP-1alpha that was down-regulated by TGF-beta whereas the induction of MIP-1beta by IPP+IL-12 was refractory to cotreatment with TGFbeta indicating that these chemokines are differentially regulated by these cytokines. Vdelta2(+) T cells also expressed a wide range of C-C chemokine receptors including CCR1, CCR5, and CCR8, all of which were down-regulated following activation. We conclude that Vdelta2(+) cells can be rapidly induced by components of bacterial cell walls to express high levels of proinflammatory chemokines, supporting an important role for these cells in the early stages of the inflammatory responses to many common pathogens. (Blood. 2000, 95:39-47)

BACKGROUND: The recognition of phosphorylated nonpeptidic microbial metabolites by Vgamma9Vdelta2 T cells does not appear to require the presence of MHC molecules or antigen processing, permitting rapid responses against microbial pathogens. These may constitute an important area of natural anti-infectious immunity. To provide evidence of their involvement in immune reactivities against mycobacteria, we measured the responsiveness of peripheral blood Vgamma9Vdelta2 T cells in children with primary Mycobacterium tuberculosis (MTB) infections. MATERIALS AND METHODS: Peripheral blood mononuclear cells from 22 children with MTB infections and 16 positivity of tuberculin (PPD)-negative healthy children were exposed to nonpeptidic antigens in vitro and the reactivity of the Vgamma9Vdelta2 T cell subset with these antigens was determined using proliferation and cytokine assays. Also, responses of gammadelta T cells from rhesus monkeys stimulated with phosphoantigens in vivo were measured. RESULTS: The Vgamma9Vdelta2 T cell responses were highly increased in infected children in comparison with age-matched controls. This augmented Vgamma9Vdelta2 T cell reactivity subsided after successful antibiotic chemotherapy, suggesting that persistent exposure to mycobacterial antigens is required for the maintenance of gammadelta T cell activation in vivo. The in vivo reactivity of Vgamma9Vdelta2 T cells to phosphoantigens was also analyzed in a rhesus monkey model system. Intravenous injections of phosphoantigens induced an activated state of simian Vgamma9Vdelta2 T cells which decreased after 2 months, i.e., with a time course similar to that seen in MTB-infected children. CONCLUSIONS: The increased reactivity of Vgamma9Vdelta2 T cells to phosphoantigens appears to be dependent on constant antigenic exposure. Consequently, the assessment of Vgamma9Vdelta2 responses may be useful for monitoring the efficacy of antimycobacterial therapies.

Viral, bacterial, protozoal, and cancer-associated Ags elicit strong responses in human gammadelta T lymphocytes. The majority of these cells in the peripheral blood express the Vgamma9Vdelta2-encoded TCR and recognize nonpeptidic phosphoantigens without an apparent MHC restriction. We have shown that Vgamma9Vdelta2 T cells express the inhibitory CD94/NKG2 receptor for HLA class I molecules. The anti-CD94 mAb inhibits 1) the Vgamma9Vdelta2 T cell proliferation in response mycobacterial phosphoantigens and 2) the HIV-induced Vgamma9Vdelta2 T cell expansion. Vgamma9Vdelta2 T cells stimulated with nonpeptidic mycobacterial antigens produce IFN-gamma and TNF-alpha. Signaling through the CD94/NKG2 receptor interferes with the synthesis of these cytokines. The CD94/HLA class I interaction is also involved in the cytotoxic activity of Vgamma9Vdelta2 T cells. The Vgamma9Vdelta2 T cell regulation through the CD94 receptor may be important for the potentially dual function in innate immunity, i.e., 1) NK-like and 2) TCR ligand-induced cytolytic activities.

The expression of heat-shock proteins (HSP) of the 72,000 MW family by Daudi and H9 lymphoma cells has been investigated by flow cytometry. It has been found that both heat-stressed and chronically human immunodeficiency virus (HIV)-infected lymphomas show an increased expression of heat-shock proteins (HSP). Moreover, murine monoclonal antibody (mAb) against 72,000 MW HSP was able to mediate antibody-dependent cellular cytotoxicity (ADCC) using peripheral blood lymphocytes (PBL) as effector cells. All target cells used in these experiments were efficiently lysed in the presence of anti-HSP antibody suggesting a role of membrane HSP in the elimination of stressed or infected cells.