Dominique Blanchard

Dendritic Cells Infiltrating Human Non-Small Cell Lung Cancer Are Blocked at Immature Stage

The efficacy of immune response to control human cancer remains controversial. It is particularly debated whether and to what extent the capacity of tumor-infiltrating dendritic cells (DC) to drive immunization can be turned off by transformed cells, leading to tumor-specific tolerance rather than immunization. To address this issue, we have characterized the DC isolated from human non-small cell lung cancer (NSCLC). These biopsy specimens contained CD11chigh myeloid DC (mDC), but also CD11c− plasmacytoid DC (pDC) and a third DC subset expressing intermediate level of CD11c. Compared with peripheral blood, CD11chigh tumor-infiltrating DC (TIDC) displayed a “semi-mature” phenotype, and TLR4 or TLR8 stimulation drove them to mature partially and to secrete limited amounts of cytokines. In contrast, most tumor-infiltrating pDC were immature but underwent partial maturation after TLR7 activation, whereas TLR9 ligation triggered low secretion of IFN-α. CD11cint mDC represented ∼25% of total DC in tumoral and peritumoral tissues and expressed low levels of costimulatory molecules contrasting with high levels of the immunoinhibitory molecule B7-H1. Finally, the poor APC function of total TIDC even after TLR stimulation and the migratory response of both tumor-infiltrating mDC and pDC toward CCL21 and SDF-1 in vitro suggested their ability to compromise the tumor-specific immune response in draining lymph nodes in vivo. Further studies will be required to establish the specific role of the three TIDC subsets in tumor immunity and to draw conclusions for the design of therapeutic strategies.

Induction of somatic mutation in a human B cell line in vitro.

Both the B cell-surface trigger(s) and the intracellular molecular mechanism(s) of somatic hypermutation in immunoglobulin (Ig) variable region genes remain unknown, partly because of the lack of a simple and reproducible in vitro model. Here, we show that upon surface immunoglobulin cross-linking followed by co-culture with activated cloned T cells, the Burkitts lymphoma cell line BL2 is induced to mutate its IgV(H) gene. Repeated activation of BL2 cells increased the frequency of mutation. The in vitro-induced mutations, which do not affect the IgM constant region, are point mutations distributed over the entire V(H)DJ(H) gene segment and do not show evidence of antigen-driven selection.

Leukemic plasmacytoid dendritic cells share phenotypic and functional features with their normal counterparts

This work aims to further characterize the newly described leukemic plasmacytoid dendritic cells (LPDC), for which we had previously demonstrated their normal, PDC‐like ability to produce IFN‐α. In addition, LPDC also express the specific antigens BDCA‐2 and BDCA‐4. Importantly, they become fully competent antigen‐presenting cells (APC) after a short maturation induced by IL‐3 + CD40L or virus, exhibiting a characteristic APC phenotype (high expression of CD83 and of the costimulatory molecules CD40, CD80, CD86). Whereas IL‐3 + CD40L‐activated LPDC prime naive CD4+ T cells towards a Th2 pathway (IL‐4‐secreting T cells), virus‐activated LPDC drive a Th1 profile (IFN‐γ–secreting T cells). Moreover, we show in one case that LPDC are able to capture, process and present exogenous antigens, leading to the activation of both CD4+ and CD8+ T cell clones in an antigen‐specific manner. This study further characterizes the phenotype and immunological functions of LPDC.

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. In the controls, IL-4 inhibited Ig production in response toStaphylococcus aureus and pokeweed mitogen stimulation. IL-2 induced maximal Ig production in association withStaphylococcus aureus, whereas it inhibited pokeweed mitogen-induced production. In patients, levels of Ig production in response to mitogens and cytokines were reduced, particularly for the response to IL 2. The inhibitory effect of IL-4 on mitogen-induced Ig production was observed in RA patients as in the controls. Spontaneous production of IL-6 was increased in RA patients. These levels were correlated with indicators of active disease such as sedimentation rate and Ritchie index. IL-4 inhibited the production of IL-6, IL-1β, and tumor necrosis factor α (TNFα) by both controls and rheumatoid patients. Thus as first described for the T-cell response, mononuclear cells from RA patients display a reduced response to mitogens and cytokines which induce their B-cell differentiation into Ig-screening cells. However, IL-4 was able to inhibit Ig and cytokine production, properties suggesting a potential antiinflammatory role for this cytokine.

Molecular control of B-cell immunopoiesis.

The function of B lymphocytes is to make antibodies in response to all different types of pathogens that invade the organism. B lymphocytes, generated through a process called lymphopoiesis in primary lymphoid organs (fetal liver, bone marrow), migrate into peripheral lymphoid organs (lymph nodes, spleen, tonsils) as mature B cells. During antigen-specific immune responses, antigen-specific naive B cells undergo a cascade of events including activation, expansion, mutations, isotype switch, selections, and differentiation into either antibody-secreting plasma cells or memory B cells. These antigen-dependent events occur in different areas of secondary lymphoid organs, as well as other nonlymphoid organs. By opposition to the antigen-independent lymphopoiesis, we propose to call the antigen-dependent events, immunopoiesis. It requires the interaction of B cells with antigens and numerous cell types including T cells, dendritic cells (DC), follicular dendritic cells (FDC), and macrophages. These cells interact with B cells through different cell surface molecules and through the release of polypeptidic mediators called cytokines. The present review summarizes the in uitro effects of recombinant cytokines on purified human B lymphocytes activated either through their antigen receptors or through their CD40 antigen, an important receptor to a T-cell activation antigen. We then try to integrate these observations into the various in uiuo sites of B-cell activation.

Supernatant from an Activated Human CD4+ T-Cell Clone Modulates the Proliferation and Collagen Synthesis of Human Dental Pulp Fibroblast

Several studies indicate a relationship between immunocompetent cells and fibroblast functions such as proliferation and collagen synthesis, which may be of importance in understanding the process of fibrosis. We demonstrate here the activity of supernatant from an activated human CD4+ proliferative T-cell clone (2F1) in stimulating the proliferation of human dental pulp fibroblasts, while inhibiting their soluble type I collagen secretion in either growing or confluent cultures. Taken together, our results indicate that T-cell derived lymphokines may be of importance in regulating normal dental pulp fibroblast functions.

A mouse monoclonal antibody against glycophorin A produced by in vitro stimulation with human red cell membranes

Human erythrocyte membranes were used as antigen for production of mouse monoclonal antibodies against blood group related structures by in vitro immunization. Culture medium supernatant of PHA and PMA stimulated mouse thymus cells was used as source of cytokines. The selected antibody designated 124,D-7 (isotype IgM) was found to directly agglutinate all human red cells, except the rare erythrocytes En(a-) which lack glycophorin A. Immunoblotting showed faint bands in the positions of glycophorin A, whereas no binding occurred to glycophorin B. Inhibition of agglutination with purified glycophorin A and peptides suggests that the epitope is located within the amino acid residues 35-40. Rat and chicken erythrocytes also reacted with the antibody, whereas mouse erythrocytes were only agglutinated at very low dilutions of ascitic fluid.