Further characterization of the sensitizing bursa cells and of the target for suppression in the transfer of agammaglobulinemia.

Presensitization of BX donors with B cells appears obligatory in order for their T cells to acquire suppressor capacity against the adoptive humoral antibody response of bursa cells to B. abortus. Although anti-Ig + C treatment of bursa cells removes their capacity to "immunize" BX chickens for suppressor activity, BX chickens cannot be sensitized for this effect by the injection of chicken IgM + IgG. Both embryonic and allogeneic bursa cells can "immunize" the T cells of BX chickens. The observation that spleen cells from BX chickens can cause absence of plasma cells and germinal centers in the spleen and mucosal lining of cecal tonsils of histocompatible recipients within 1-2 weeks after transfer suggests that the suppressor cells mediate their effect by acting directly on B cells at one or more stages during their development.