Selection of T cell clones expressing high-affinity public TCRs within Human cytomegalovirus-specific CD8 T cell responses.

Assessment of clonal diversity of T cell responses against human CMV (HCMV), a major cause of morbidity in immunodepressed patients, provides important insights into the molecular basis of T cell immunodominance, and has also clinical implications for the immunomonitoring and immunotherapy of HCMV infections. We performed an in-depth molecular and functional characterization of CD8 T cells directed against an immunodominant HLA-A2-restricted epitope derived from HCMV protein pp65 (NLV/A2) in steady state and pathological situations associated with HCMV reactivation. NLV/A2-specific T cells in healthy HCMV-seropositive donors showed limited clonal diversity and usage of a restricted set of TCR Vbeta regions.

Increased soluble and platelet-associated CD40 ligand in essential thrombocythemia and reactive thrombocytosis.

CD40 ligand (CD40L) is expressed on activated CD4(+) T lymphocytes and at the activated platelet surface. A circulating soluble form of CD40L (sCD40L) is generated by the way of a proteolytic cleavage. We measured sCD40L in the plasma of either healthy subjects; patients with inflammatory disorders and low, normal, or high platelet count (reactive thrombocytosis); or patients with essential thrombocythemia (ET).

CD40-ligand stimulates myelopoiesis by regulating flt3-ligand and thrombopoietin production in bone marrow stromal cells.

CD40 ligand (CD40L)/CD40 interactions play a central role in T-cell-dependent B-cell activation as previously shown by in vitro studies, the phenotype of CD40L knockout mice and the defective expression of CD40L in patients who have X-linked immunodeficiency with hyper-IgM. The distribution of CD40 in cells other than of myeloid and lymphoid lineages has suggested additional functions for this receptor/ligand couple. Here we show that CD40L stimulates myelopoiesis with a noticeable effect on megakaryocytopoiesis in cocultures of hematopoietic progenitor cells and bone marrow stromal cells.

Implication of gammadelta T cells in the human immune response to cytomegalovirus.

In normal individuals, gammadelta T cells account for less than 6% of total peripheral T lymphocytes and mainly express T-cell receptor (TCR) Vdelta2-Vgamma9 chains. We have previously observed a dramatic expansion of gammadelta T cells in the peripheral blood of renal allograft recipients only when they developed cytomegalovirus (CMV) infection. This increase was long lasting (more than 1 year), was associated with an activation of gammadelta T cells, and concerned only Vdelta1 or Vdelta3 T-cell subpopulations.

An enlarged subpopulation of T lymphocytes bearing two distinct gammadelta TCR in an HIV-positive patient.

Although T cell clone monospecificity is ensured by several allelic exclusion processes operating at either the genotypic or phenotypic levels, clones expressing two distinct alphabeta or gammadelta TCR have been described in several instances. Thus far, the origin of dual TCR-expressing cells and the homeostatic mechanisms controlling the size of this subset in the periphery remain poorly understood. In the course of a phenotypic analysis of gammadelta T cells in HIV-infected patients, we detected the presence of a T cell subset stained by both Vdelta2- and Vdelta3-specific mAb, which represented a large fraction (up to 16.

Major expansion of gammadelta T lymphocytes following cytomegalovirus infection in kidney allograft recipients.

In normal persons, circulating gammadelta T cells comprise a minor cell subset (0.5%-6% of total lymphocytes). gammadelta T cells were studied in the context of therapeutic immunosuppression in transplanted patients.

CD40 ligand stimulates proinflammatory cytokine production by human endothelial cells.

Functional expression of CD40 has recently been described on the surface of HUVEC, and activation of these cells with CD40 ligand (CD40-L) leads to increased adhesion molecule expression. Here, we analyzed the effect of CD40 triggering on cytokine production by HUVEC. CD40-L-transfected fibroblasts, in contrast to their untransfected counterparts, as well as a soluble recombinant human CD40-L/murine CD8alpha chimeric molecule were able to importantly increase (by a mean of fourfold) the production of leukemia inhibitory factor (LIF) by HUVEC.

Leukemia inhibitory factor: part of a large ingathering family.

Leukemia Inhibitory Factor (LIF) has a wide variety of biological activities. It regulates the differentiation of embryonic stem cells, neural cells, osteoblasts, adipocytes, hepatocytes and kidney epithelial cells. It also triggers the proliferation of myoblasts, primordial germ cells and some endothelial cells.

Bcl-2+ tonsillar plasma cells are rescued from apoptosis by bone marrow fibroblasts.

Plasma cells represent the final stage of B lymphocyte differentiation. Most plasma cells in secondary lymphoid tissues live for a few days, whereas those in the lamina propria of mucosa and in bone marrow live for several weeks. To investigate the regulation of human plasma cell survival, plasma cells were isolated from tonsils according to high CD38 and low CD20 expression.

Generation of memory B cells and plasma cells in vitro.

After germinal center B cells undergo somatic mutation and antigen selection, they become either memory B cells or plasma cells, but the signal requirements that control entry into either pathway have been unclear. When purified human germinal center cells were cultured with interleukin-2, interleukin-10, and cells expressing CD40 ligand, cells with characteristics of memory B cells were generated. Removal of CD40 ligand from the system resulted in terminal differentiation of germinal center B cells into cells with the characteristics of plasma cells.

T cell-induced B cell blasts differentiate into plasma cells when cultured on bone marrow stroma with IL-3 and IL-10.

B lymphocytes activated by T cells in secondary lymphoid organs mature into plasma cells after migration into the medullary cords of these organs, mucosal lamina propria or bone marrow. To analyze each step leading to plasma cell generation, we set up a two-step culture system of purified tonsillar B cells. In a primary stage, B cell blasts were generated by co-culturing B cells with an irradiated T cell clone activated with immobilized anti-CD3.

Balance of IL-1 receptor antagonist/IL-1 beta in rheumatoid synovium and its regulation by IL-4 and IL-10.

The spontaneous production of IL-1 beta (IL-1 beta) and IL-1 receptor antagonist (IL-1Ra) by rheumatoid arthritis (RA) synovium, and the regulation of their production by IL-4 and IL-10, were studied. Supernatants from cultured synovium pieces from 19 RA patients were assayed for IL-1 beta and IL-1Ra production using ELISA and RIA, respectively. After 10 days of culture, spontaneous production of IL-1Ra was 1.

Interleukin 4, but not interleukin 10, regulates the production of inflammation mediators by rheumatoid synoviocytes.

Rheumatoid synovitis is characterized by increased activation and proliferation of synoviocytes, which are an important source of cytokines. The role of Interleukin 4 (IL-4) and IL-10 on the production of mediators of inflammation by rheumatoid synoviocytes was studied herein. While IL-4 weakly affected the spontaneous PGE2 production, it strongly inhibited its production when cells were stimulated with IL-1 beta and TNF-alpha.

The ability of synoviocytes to support terminal differentiation of activated B cells may explain plasma cell accumulation in rheumatoid synovium.

To understand the accumulation of plasma cells within RA synovium, the ability of rheumatoid synoviocytes to support the differentiation of B cells into plasma cells was explored. Tonsillar B lymphocytes cultured over confluent monolayers of synoviocytes, secreted threefold more Igs (mainly IgM) than B cells cultured directly on plastic well. More importantly, synoviocytes enhanced by 14-fold the production of Igs (mainly IgG) by B cells costimulated with Staphylococcus aureus Cowan (SAC) particles.

Interleukin-4 inhibits bone resorption through an effect on osteoclasts and proinflammatory cytokines in an ex vivo model of bone resorption in rheumatoid arthritis.

Objective: To assess local bone resorption in the context of rheumatoid synovitis and its modulation by interleukin-4 (IL-4).

Methods: We developed an ex vivo model of bone resorption using juxtaarticular samples of bone obtained during joint surgery. We studied the histomorphometric parameters of bone resorption and the regulation of the production of IL-6, leukemia inhibitory factor (LIF), and the collagen cross-link pyridinoline, which is released during bone resorption in vivo.

Interleukin-4 but not interleukin-10 inhibits the production of leukemia inhibitory factor by rheumatoid synovium and synoviocytes.

The expression of the proinflammatory cytokine leukemia inhibitory factor (LIF) has been reported in the cartilage and synovium of rheumatoid arthritis (RA) patients. Here, we show that high levels of LIF were constitutively produced by cultures of synovium pieces. Low levels of LIF were produced spontaneously by isolated synoviocytes, but interleukin (IL)-1 beta caused a fourfold enhancement of this secretion.

IL-4 inhibits growth factor-stimulated rheumatoid synoviocyte proliferation by blocking the early phases of the cell cycle.

A major feature of rheumatoid arthritis is an uncontrolled proliferation of synoviocytes. This is consistent with the active production of factors such as platelet-derived growth factor (PDGF) and IL-1 by the synovitis, which act in vivo as well as in vitro as potent synoviocyte growth factors. We have previously shown that IL-4 is able to inhibit growth factor production in an ex vivo model of synovitis.

Inhibition of the production of proinflammatory cytokines and immunoglobulins by interleukin-4 in an ex vivo model of rheumatoid synovitis.

Objective: To assess the spontaneous production of proinflammatory cytokines and immunoglobulins in rheumatoid arthritis (RA) synovitis and modulation by interleukin-4 (IL-4).

Methods: We developed an ex vivo model of RA synovitis using pieces of RA synovium, and have studied the regulation of the production of IL-1 beta, IL-6, tumor necrosis factor alpha (TNF alpha), IgM, and IgG.

Results: Spontaneous production of proinflammatory cytokines in vitro was active, with prolonged cytokine gene transcription and translation.

Interleukin 4 inhibits polyclonal immunoglobulin secretion and cytokine production by peripheral blood mononuclear cells from rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is associated with T- and B-cell dysfunction. Immunoglobulin (Ig) production is under the control of T cells and their derived cytokines such as interleukin 2 (IL-2) and IL-4. Herein we studied the regulation of the production of immunoglobulins and cytokines by peripheral blood mononuclear cells from RA patients and controls.