DOES THE AVAILABILITY OF EITHER B-CELLS OR CD4+ CELLS LIMIT GERMINAL CENTER FORMATION

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  • 1 March 1990
    • journal article
    • research article
    • Vol. 69  (3) , 487-489
Abstract
To determine whether the availability of either B cells or T cells regulates the number and size of germinal centres observed following antigenic challenge, irradiated PVG rats were reconstituted with limiting numbers of thoracic duct B cells (with excess T cells) or with limiting numbers of thoracic duct CD4+ cells (with sufficient B cells). Germinal centre formation was measured histologically in the spleens of reconstituted rats 7 days after immunization with 2 .times. 109 sheep erythrocytes (at the height of the germinal centre reaction). Although reconstitution with B cells and antigen alone, or with thymocytes and antigen alone, produced no germinal centres, saturating numnbers of germinal centres on the order observed for normal, non-irradiated rats were observed in irradiated rats reconstituted with only 107 B cells and 5 .times. 106 CD4+ cells. Germinal centres in the spleens of minimally reconstituted rats were also comparable in size to those observed in normal rats. Reconstitution with either 4 .times. 107 thoracic duct lymphocytes (including 2 .times. 107 B cells, as well as CD8+ and CD4+ cells) or with 4 .times. 107 thoracic duct lymphocytes and 2 .times. 108 thymocytes also led to saturating numbers of germinal centres. It is concluded therefore that (i) CD4+ cells are sufficient for the T-cell contribution required for germinal centre formation, and (ii) some factor other than the availability of B cells or CD4+ cells normally limits germinal centre formation.