Negative Selection of Human Germinal Center B Cells by Prolonged Bcr Cross-linking

The antigen receptors on T and B lymphocytes can transduce both agonist and antagonist signals leading either to activation/survival or anergy/death. The outcome of B lymphocyte antigen receptor (BCk) triggering depends upon multiple parameters which include (a) antigen concentration and valency, (b) duration of BCP,. occupancy, (c) receptor affinity, and (d) B cell differentiation stages. Herein, using anti-immunoglobulin K and k light chain antibodies, we analyzed the response of human naive, germinal center (GC) or memory B cells to BC R crosslinking regardless of heavy chain Ig isotype or intrinsic BCR specificity. We show that after CD40-activation, anti-BCR.(K+k) can elicit an intracellular calcium flux on both GC and non-GC cells. However, prolonged BCP, cross-linking induces death of CD40-activated GC B cells but enhances proliferation of naive or memory cells. Anti-K antibody only kills K + GC B cells without affecting surrounding k + GC B cells, thus demonstrating that BCR-mediated killing of GC B lymphocytes is a direct effect that does not involve a paracrine mechanism. BCR-mediated killing of CD40-activated GC B cells could be partially antagonized by the addition of IL-4. Moreover, in the presence of IL-4, prestimulation through CD40 could prevent subsequent anti-Ig-mediated cell death, suggesting a specific role of this combination in selection of GC B cells. This report provides evidence that in human, susceptibility to BCP, killing is regulated along peripheral B cell differentiation pathway.