Regulation of Antibody Response in Vitro

Abstract

Mesenteric lymph node cells were obtained from rabbits that were primed with dinitrophenylated ragweed antigen (DNP-Rag) and supplemented with free Ascaris antigen (Asc); in vitro anti-hapten antibody response of the primed cells was studied. It was found that stimulation of Rag-sensitized cells with free Rag enhanced anti-DNP antibody response to DNP-unrelated carrier conjugate (DNP-KLH) but suppressed the response of the same cell suspension to DNP-Asc. It was also found that both IgG and IgE antibody responses to DNP-Rag were suppressed by the addition of free Asc with the homologous antigen. Mechanisms involved in the enhancement and suppression of antibody response by free carrier were explored with cell-free supernatant (CFS) obtained from the culture of primed lymph node cells with free carrier. The results showed that essentially all CFS preparations studied enhanced antibody response when they were added to primed lymph node cells which had been treated with a hapten-protein conjugate. Some of the CFS preparations, however, suppressed antibody response of the same primed cells, if they were added to the cells together with the antigen. Evidence was obtained which indicated that suppression of the antibody response by CFS is not due to an excess amount of enhancing soluble factor. Several preparations of CFS were incubated with the same primed cell suspension, either before or after incubation with antigen, to determine their suppressive effect and enhancing effect. The results showed that suppressive effect of CFS on the unstimulated cells did not correlate with their enhancing effect on the antigen-stimulated cells. The experiment eliminated the possibility that the same T cell factor expresses two opposite effects depending on the stage of B cell differentiation, and suggested the presence of both suppressive and enhancing soluble factors in the preparations of cell free supernatant.

The experiment also showed that enhancing soluble factor for IgE antibody response was obtained from carrier-specific cells primed with alum-precipitated antigen but the cells proliferated by the immunization with the carrier included in complete Freund's adjuvant did not release the enhancing soluble factor for IgE. It was also found that enhancing soluble factor for IgG antibody neither enhanced nor suppressed IgE antibody response.