Engagement of OX40 enhances antigen-specific CD4(+) T cell mobilization/memory development and humoral immunity: comparison of alphaOX-40 with alphaCTLA-4.
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Increasing the long-term survival of memory T cells after immunization is key to a successful vaccine. In the past, the generation of large numbers of memory T cells in vivo has been difficult because Ag-stimulated T cells are susceptible to activation-induced cell death. Previously, we reported that OX40 engagement resulted in a 60-fold increase in the number of Ag-specific CD4(+) memory T cells that persisted 60 days postimmunization. In this report, we used the D011.10 adoptive transfer model to examine the kinetics of Ag-specific T cell entry into the peripheral blood, the optimal route of administration of Ag and alphaOX40, and the Ag-specific Ab response after immunization with soluble OVA and alphaOX40. Finally, we compared the adjuvant properties of alphaOX40 to those of alphaCTLA-4. Engagement of OX-40 in vivo was most effective when the Ag was administered s.c. Time course studies revealed that it was crucial for alphaOX40 to be delivered within 24-48 h after Ag exposure. Examination of anti-OVA Ab titers revealed a 10-fold increase in mice that received alphaOX40 compared with mice that received OVA alone. Both alphaOX40 and alphaCTLA-4 increased the percentage of OVA-specific CD4(+) T cells early after immunization (day 4), but alphaOX40-treated mice had much higher percentages of OVA-specific memory CD4(+) T cells from days 11 to 29. These studies demonstrate that OX40 engagement early after immunization with soluble Ag enhances long-term T cell and humoral immunity in a manner distinct from that provided by blocking CTLA-4. (+info)
Bi-directional modulation of T cell-dependent antibody production by prostaglandin E(2).
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T cell-dependent Ig production involves interaction between T cells and B cells. This study evaluated the effects of prostaglandin (PG) E(2) on Ig production in a system in which B cells were co-cultured with autologous CD4(+) T cell clones non-specifically activated by anti-CD3. The effects of PGE(2) on T cell-dependent Ig production differed substantially, depending on the T cells employed. We selected six T cell clones that were able to enhance Ig production (resistant T cell clones) and six T cell clones that inhibited Ig production in the presence of PGE(2) (sensitive T cell clones) for comparison. The resistant T cells produced high levels (>1000 pg/ml) of IL-2 and/or IL-4, and expressed high CD40L, OX40 and CD45RA, and low CD45RO. In contrast, sensitive T cells secreted low IL-2 (<500 pg/ml) and IL-4 (<200 pg/ml), and expressed low CD40, OX40 and CD45RA, and high CD45RO. Adding supernatant derived from resistant T cell clones restored Ig production inhibited by PGE(2), while removing IL-2, IL-4 or IL-10 using specific antibodies inhibited Ig production. In addition, we demonstrated a direct effect of PGE(2) on B cells to enhance Ig production. Consistently, in the presence of resistant T cells, PGE(2) increased B cell proliferation and differentiation. In conclusion, the effects of PGE(2) on Ig production consist of its indirect effects through T cells and its direct effects on B cells. The outcome of the effects can be up-regulatory or down-regulatory, depending whether resistant or sensitive T cells are involved. (+info)
Ox40 costimulation enhances the development of T cell responses induced by dendritic cells in vivo.
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Dendritic cells (DCs) are bone marrow-derived APCs that display unique properties aimed at stimulating naive T cells. Several members of the TNF/TNFR families have been implicated in T cell functions. In this study, we examined the role that Ox40 costimulation might play on the ability of DCs to regulate CD4(+) and CD8(+) T cell responses in vivo. Administration of anti-mouse Ox40 mAb enhanced the Th response induced by immunization with Ag-pulsed DCs, and introduced a bias toward a Th1 immune response. However, anti-Ox40 treatment enhanced the production of Th2 cytokines in IFN-gamma(-/-) mice after immunization with Ag-pulsed DCs, suggesting that the production of IFN-gamma during the immune response could interfere with the development of Th2 lymphocytes induced by DCs. Coadministration of anti-Ox40 with DCs during Ag rechallenge enhanced both Th1 and Th2 responses induced during a primary immunization with DCs, and did not reverse an existing Th2 response. This suggests that Ox40 costimulation amplifies an ongoing immune response, regardless of Th differentiation potential. In an OVA-TCR class II-restricted adoptive transfer system, anti-Ox40 treatment greatly enhanced the level of cytokine secretion per Ag-specific CD4(+) T cell induced by immunization with DCs. In an OVA-TCR class I-restricted adoptive transfer system, administration of anti-Ox40 strongly enhanced expansion, IFN-gamma secretion, and cytotoxic activity of Ag-specific CD8(+) T cells induced by immunization with DCs. Thus, by enhancing immune responses induced by DCs in vivo, the Ox40 pathway might be a target for immune intervention in therapeutic settings that use DCs as Ag-delivery vehicles. (+info)
The different process of class switching and somatic hypermutation; a novel analysis by CD27(-) naive B cells.
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The relationship between class switch recombination (CSR) and somatic hypermutation has been unclear. By using human CD27(-) naive B cells, we investigated the somatic hypermutation and producibility of immunoglobulins (Igs) that occur after CSR. Although neither adult CD27(-) nor cord blood B cells, which showed the unmutated Ig V-region genes, produced IgG, IgM, or IgA in response to conventional stimuli, they produced IgG and IgM but not IgA in the presence of Staphylococcus aureus Cowan strain (SAC) + interleukin-2 (IL-2) + IL-10 + anti-CD40 mAb + CD32 transfectants (CD40/CD32T). The naive B cells also produced IgE when combined with IL-4 + CD40/CD32T. In parallel with IgG production, the expression of mature gamma1 and gamma 2 transcripts was induced from naive B cells by the stimuli. The CD27 expression on human naive B cells was induced remarkably by CD40 signaling or B-cell receptor engagement, but somatic hypermutation could not be induced. The proliferation and differentiation into plasma cells were induced from naive B cells, whereas most of the plasma cells displayed very low levels of mutations in Ig V-region genes. CD27(-) naive B cells expressed activation-induced cytidine deaminase messenger RNA by the stimuli later than CD27(+) memory B cells. Our results demonstrate that CSR, but not noticeable somatic hypermutation, can be induced from CD27(-) naive B cells upon B-cell receptor engagement and CD40 signaling in cooperation with cytokines, suggesting that CSR and somatic hypermutation processes can occur independently, and the antibodies produced in this in vitro system are low-affinity antibodies. (+info)
Lack of CD27-CD45RA-V gamma 9V delta 2+ T cell effectors in immunocompromised hosts and during active pulmonary tuberculosis.
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In humans, the circulating pool of mycobacteria-reactive Vgamma9Vdelta2+ T cells is expanded with age and may contribute to Mycobacterium tuberculosis immunosurveillance. We observed that two subsets of Vgamma9Vdelta2+ T cells could be identified on the basis of CD27 expression in immunocompetent adults, showing that functionally differentiated gammadelta T cells have lost CD27 expression. In contrast, the CD27-CD45RA-Vgamma9Vdelta2+ T cell subset of effector cells was absent in cord blood cells from healthy newborns and lacking in the peripheral blood from HIV-infected patients. Moreover, circulating Vgamma9Vdelta2+ T cell effectors were significantly reduced in patients with acute pulmonary tuberculosis, resulting in a reduced frequency of IFN-gamma-producing cells after stimulation with nonpeptidic mycobacterial ligands. These observations indicate that monitoring and boosting gammadelta T cell effectors could be clinically relevant both in immunocompromised hosts and during active tuberculosis disease. (+info)
Severe deficiency of switched memory B cells (CD27(+)IgM(-)IgD(-)) in subgroups of patients with common variable immunodeficiency: a new approach to classify a heterogeneous disease.
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Hypogammaglobulinemia is the hallmark of common variable immunodeficiency (CVID) syndrome, a heterogeneous disorder predisposing patients to recurrent bacterial infections. In this study, we investigated the peripheral B-cell compartment of 30 well-characterized CVID patients in comparison to 22 healthy controls. Flow cytometric analysis of peripheral blood lymphocytes revealed a reduction of class-switched CD27(+)IgM(-)IgD(-) memory B cells below 0.4% in 77% of our patients (group I), while this B-cell subpopulation exceeded 0.5% in all healthy donors and in 23% of CVID patients (group II). These results correlate well with the capacity of peripheral blood lymphocytes to produce immunoglobulins in vitro upon stimulation with Staphylococcus aureus Cowan I (SAC) plus interleukin-2 because the production of immunoglobulin G in vitro is entirely dependent on the presence of switched memory B cells. The subdivision of group I into patients with an increased proportion of CD21(-) peripheral B cells (> 20%; group Ia) and patients with normal percentages of CD21(-) B cells (< 20%; group Ib) revealed a significant clustering of patients with splenomegaly and autoimmune cytopenias in group Ia. Based on these observations, we propose a fast and reliable new classification for CVID patients by flow cytometric quantification of class-switched memory and immature B cells in the peripheral blood of patients. Our results point toward defects at various stages of B-cell differentiation in CVID subgroups and support the value of a B-cell-oriented classification principle. A consensus on this new classification system will hopefully provide a tool for rapidly defining homogeneous subgroups of CVID for functional studies and genetic linkage analysis. (+info)
Long-lasting memory-resting and memory-effector CD4+ T cells in human X-linked agammaglobulinemia.
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Conflicting results obtained from animal studies suggest that B cells play a role in maintaining long-term T-cell memory and in skewing T-cell response toward a T-helper 2 (T(H)2) phenotype. X-linked agammaglobulinemia (XLA) is a genetic human disease characterized by the lack of circulating B cells due to the mutation of Bruton tyrosine kinase. This disease thus represents a unique model for studying the role of B lymphocytes in regulating T-cell functions in humans. To this aim, we analyzed hepatitis B envelope antigen (HBenvAg)-specific T-cell memory in a series of XLA patients vaccinated against hepatitis B virus (HBV). We found HBenvAg-specific T lymphocytes producing interferon-gamma, interleukin-4, or both in the peripheral blood of XLA patients up to at least 24 months after completing the standard anti-HBV immunization protocol. The HBenvAg-specific T-cell frequencies and the percentage of patients with these responses were not significantly different from healthy vaccinated controls. By combining cell purification and enzyme-linked immunospot assay, we found that effector CD27- T cells, which promptly produced cytokines in response to antigen (Ag), and memory-resting CD27+ T cells, which required Ag restimulation to perform their functions, were maintained in both XLA patients and controls for up to 24 months after the last vaccination boost. These data strongly suggest that B cells are not an absolute requirement for the generation of effective T-cell memory in humans, nor do they seem to influence T(H)1/T(H)2 balance. (+info)
Naive CD4+ T cells exhibit distinct expression patterns of cytokines and cell surface molecules on their primary responses to varying doses of antigen.
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The amount of an Ag used for stimulation affects the type and magnitude of T cell responses. In this study we have investigated the primary response of naive CD4(+) T cells derived from OVA-specific TCR-transgenic mice (OVA23-3) upon stimulation with varying doses of the antigenic peptide, OVA(323-339). IL-4 expression was maximal with 50 nM Ag and decreased significantly with increasing doses. In contrast, IFN-gamma expression, which was also detected at 50 nM Ag, increased with increasing doses. The expression patterns of mRNA for the Th2-specific transcription factors GATA-3 and c-Maf were parallel to that of IL-4. These expression profiles were not altered by the addition of anti-IL-4 plus anti-IL-12 mAbs, suggesting that cytokine receptor signaling is not essential. Naive CD4(+) T cells stimulated with 5 nM Ag elicited IgM secretion from cocultured B cells, whereas those stimulated with 50 nM Ag or more elicited apoptosis of B cells. This may be because at lower doses of Ag (5 nM), naive CD4(+) T cells express CD40 ligand and OX40, whereas at higher doses (50 nM), they express Fas ligand. Clearly, the expression of each type of molecule depends on the Ag dose, and different molecules had different expression patterns. Thus, in the primary response, naive CD4(+) T cells can exhibit different functions depending on the dose of Ag. (+info)