Human Germinal Center CD4

Journal of Immunology Research, Aug 2018

We have isolated two subtypes of helper T cells from human tonsils: CD4

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Human Germinal Center CD4

Human Germinal Center CD4 / CD57 / T Cells Act Differently On B Cells Than Do Classical T-Helper Cells FARIDA BOUZAHZAH ALAIN BOSSELOIR ERNST HEINEN LtON J. SIMAR 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. Germinal center; T-helper cells; CD57 T cells; cell proliferation INTRODUCTION T lymphocytes purified from human tonsils are mainly CD4 cells (Sugiyama et al., 1976, 1984, 1987; Plum et al., 1987) , CD8 T cells being proportionally less numerous in tonsils than in the peripheral blood (Sugiyama et al., 1987). The prevalence of CD4 cells in tonsils suggests that tonsillar T lymphocytes are functionally oriented to helper activity (Sugiyama et al., 1987) . Several immunohistochemical studies have revealed the existence of tonsillar T cells expressing the CD57 antigen characteristic of cells with NK activity (Okada et al., 1988) . These cells are essentially located in the GC light zone; a few are also found in the interfollicular T-dependent areas and the mantle zones (Bouzahzah et al., 1993) . In a previous ultrastrutural morphological study, we have shown that these cells are medium-sized and do not contain the large granules typical of blood NK cells (Bouzahzah et al., 1993) . Phenotypically, these cells do not express Leu 8, CD16, or CD11b, so they clearly differ from classical NK cells (Si and Whiteside, 1983; Verlardi et al., 1985, 1986a) . These CD4 CD57 cells do not express CD25 (IL-2 receptor), CD71 (transferrin receptor), or HLA-DR, but do express CD69 (Bowen et al., 1991). Thus, they should be viewed as preactivated rather than fully activated cells. Their to much debated ability produce cytokines is (Velardi et al., 1986b; Bosseloir et al., 1989 , 1991; There is no available data as to the function of CD4 /CD57 /cells. In this report, we compare the effects of CD4 CD57 and CD4 CD57- cells on B-cell proliferation and differentiation in Igsecreting cells. Using several procedures (nylon wool columns, and selections by dynabeads and MACS), we have purified both populations of Thelper cells and cocultured them with B cells isolated from tonsils. We have compared the capacity of B cells to incorporate tritiated thymidine or to produce IgM or IgG in these two types of coculture. We pretreated the T-cell populations with mitomycin C to prevent their multiplication but added various activators to the cultures. In another series of experiments, we tested the cytotoxicity of CD4 CD57- and CD4 CD57 in the presence of K562 target cells. 11000. 8800 000 4400 2200 o/ RESULTS Effects of CD57 Proliferation and CD57- T Cells on B-cell To test the effects of CD57 and CD57- cells on B-cell proliferation, cell populations enriched in these cells were added to highly purified B cells. The purity of the T-cell populations used, as estimated by flow cytometry, exceeded 94% (CD57 cells) or 96% (CD57- cells). Before being cocultured, the T-cell populations were treated with mitomycin C to minimize their capacity to incorporate [3H]thymidine. The cells were stimulated, however, with PHA (2 tg/ml) to keep them activated. As a control, B cells were cultured alone. Little or no proliferative activity was observed in B-cell populations cultured alone or in mitomycin (...truncated)


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Farida Bouzahzah, Alain Bosseloir, Ernst Heinen, Léon J. Simar. Human Germinal Center CD4, Journal of Immunology Research, 4, DOI: 10.1155/1995/76790