|Reference : Human germinal center CD4+CD57+ T cells act differently on B cells than do classical T-h...|
|Scientific journals : Article|
|Life sciences : Anatomy (cytology, histology, embryology...) & physiology|
|Human germinal center CD4+CD57+ T cells act differently on B cells than do classical T-helper cells.|
|Bouzahzah, F. [> > > >]|
|Bosseloir, A. [> > > >]|
|Heinen, Ernst [Université de Liège - ULg > Département des sciences biomédicales et précliniques > Histologie humaine >]|
|Simar, L. J. [> > > >]|
|Taylor & Francis|
|[en] Antigens, CD4/metabolism ; Antigens, CD57/metabolism ; B-Lymphocytes/immunology ; CD4-Positive T-Lymphocytes/cytology/immunology ; Cytotoxicity, Immunologic ; Humans ; Immunoglobulins/biosynthesis ; Lymphocyte Activation ; Lymphocyte Cooperation ; Palatine Tonsil/cytology/immunology ; T-Lymphocyte Subsets/cytology/immunology ; T-Lymphocytes, Helper-Inducer/cytology/immunology ; Tumor Cells, Cultured|
|[en] We have isolated two subtypes of helper T cells from human tonsils: CD4+CD57+ cells, mostly located in the germinal center (GC), and CD4+CD57- cells, distributed through the interfollicular areas but also present in the GC. In a functional study, we have compared the capacities of these T-cell subtypes to stimulate B cells in cocultures. In order to block T-cell proliferation while maintaining their activation level, we pretreated isolated T cells with mitomycin C prior to culture in the presence of B cells and added polyclonal activators such as PHA and Con A, combined or not with IL-2. Contrary to CD4+ CD57- cells, CD4+CD57+ cells did not markedly enhance B-cell proliferation. Even when sIgD.B cells typical of germinal center cells were tested, the CD4+CD57+ cells had no significant effect. This is in accordance with the location of these cells: They mainly occupy the light zones of the GC where few B cells divide. Even when added to preactivated, actively proliferating cells, CD4+CD57 cells failed to modulate B-cell multiplication. On the supernatants of B-cell-T-cell cocultures, we examined by the ELISA technique the effect of T cells on Ig synthesis. Contrary to CD57+ T cells, whose effect was strong, CD57- T cells weakly stimulated Ig synthesis. More IgM than IgG was generally found. Because CD57 antigen is a typical marker of natural killer cells, we tested the cytolytic activity of tonsillar CD4+CD57+ cells on K562 target cells. Unlike NK cells, neither CD4+CD57+ nor CD4+CD57- cells exhibit any cytotoxicity. Thus, germinal center CD4+CD57+ cells are not cytolytic and do not strongly stimulate either B-cell proliferation or Ig secretion. CD4+CD57- cells, however, enhance B-cell proliferation and differentiation, thus acting like the classical helper cells of the T-dependent areas.|
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