Suppression and Enhancement of the Rabbit Primary in Vitro Antibody Response with Anti-Allotype Antibody: Concurrent Effects on Thymidine Incorporation, Blastogenesis, and Cell Surface Ig

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Abstract
We have adapted an in vitro culture system to study the dose-dependent effects of purified anti-light chain allotype (b4 or b5) antibody on the primary Ab response of rabbit spleen cells to sheep erythrocytes. At high doses, anti-b4 or anti-b5 Ab suppressed the anti-SRBC response and the expression of cell surface immunoglobulins while stimulating blastogenesis and thymidine incorporation. At low doses, anti-allotype Ab markedly enhanced the immune response and, to a lesser extent, thymidine incorporation and blastogenesis. The mitogenic effect of anti-allotype Ab was observed in the absence of antigen only at the higher doses. When tested on heterozygous b4b5 SpC, the high and low doses of Ab selectively modulated the immune response with respect to cells bearing the target allotype. In vivo induced allotype suppression could not be reversed by culturing SpC with high or low doses of purified anti-allotype Ab directed against the expressed allotype. Our data support the concept that anti-Ig Ab reacts directly with B cell surface Ig to trigger a mitogenic response. This trigger, however, is not sufficient to induce differentiation to anti-SRBC secreting cells in the absence of the antigen.