FEEDBACK SUPPRESSION OF B-CELL COLONY FORMATION BY SUPERNATANTS OF B-COLONY CELLS - ROLE OF IMMUNOGLOBULIN

We have reported previously that CD5+ B cells from mature B cell colon ies provide a negative feedback signal to the growth of autologous B c ell colonies. Now we have observed that supernatants from mature B cel l colonies also provide a negative feedback signal to the growth of au tologous B cell colonies. We investigated the mechanism of this effect by growing B cell colonies physically separated by a 0.45 mu m filter from T cells in millicell-CM chambers. Addition of colony supernatant s to the T cell compartment reduced the number of B cell colonies by 2 8+/-6%. Colony numbers were reduced by 11+/-2 and 17+/-5% when the sup ernatants were added to the B cell or to both compartments, respective ly. Pulsing T cells with the B cell colony supernatants before adding them to the colonies also decreased colony numbers by 33+/-13%. The ad dition of exogenous Ig classes and Ige subclasses to B cells decreased B cell colony numbers, although the effect was variable. In the prese nce of T cells, IgG had the greatest suppressive activity and the subc lass IgG(4) was most suppressive. In the absence of T cells, high conc entrations of IgG almost abolished B cell colony formation. We conclud e that these supernatants provide a negative feedback signal either di rectly to B cells, or via T cells which may be mediated at least in pa rt by Ig.