Human immune response to group A streptococcal carbohydrate (A-CHO) III. Comparison of the efficiencies of anti-idiotopic antibody and of nominal antigen in the induction of IgM anti-A-CHO-producing B cells

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Abstract
In this study the efficiencies of a monoclonal anti‐idiotopic (Id) antibody (anti‐Id498) and of various preparations of nominal antigen in the induction of an antigen‐specific human B cell response in vitro were compared. Anti‐Id498 recognizes a recurrent, binding site‐related Id present on IgM antibodies with specificity for N‐acetyl‐D‐glucosamine, the immunodominant group of streptococcal group A carbohydrate (A‐CHO). We have previously shown that anti‐Id498 induces IgM anti‐A‐CHO secretion from B cells of donors that possess Id‐498+ antibodies in their serum. A‐CHO was presented to B cells either in soluble or insoluble form, i.e. coupled to beads or as intact bacteria. Purified blood B cell populations from three Id′ healthy donors with high numbers of circulating anti‐A‐CHO B cells were used and antibody‐producing B cells are enumerated in a single‐cell assay (spot ELISA). The data show that anti‐Id498 was superior in the induction of IgM anti‐A‐CHO‐secreting B cells in two donors (factor 4.6 and 13.5 as compared to the most efficient antigenic stimulation). In the third donor antigen stimulation was slightly more efficient than anti‐Id but only with Sepharose‐bound A‐CHO and not with soluble A‐CHO or intact bacteria. The increase of specific B cells induced after stimulation with anti‐Id498 could be abolished after addition of autologous T cells in two donors. On the contrary, an enhancement of the specific response was observed after addition of autologous T cells in antigen‐stimulated cultures. Neither suppression nor enhancement were induced by addition of irradiated T cells.

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