A myeloma M 104E private idiotope is represented predominantly among anti-dextran, peritoneal cavity Ly-1+ precursor B cells.

Public and private idiotopes (Id) had been defined in the BALB/c anti-dextran B1355 fraction S (Dex) response by means of syngeneic monoclonal anti-M 104E Id antibodies. Most of the primary anti-Dex antibodies shared the public Id-1 while the private Id-5 constituted a comparatively low, but highly variable proportion of humoral anti-Dex antibodies of individual mice. In the present work we have analyzed by limiting dilution the expression of these two Id by anti-Dex B cell precursors from the spleen and peritoneal cavity of BALB/c mice. Testing spleen cells we found about 65% of anti-Dex precursors to be Id-1+ and only a minority to be Id-5+. Treatment with anti-Ly-1 and complement was without any effect on anti-Dex precursors from spleen. Anti-Dex B cell precursors among peritoneal cavity lymphocytes differed from those found in the spleen in two ways. First, on average, 50% of them were Id-5+; second, about 80% carried the Ly-1 marker. Both markers are, therefore, expressed on at least 30% of anti-Dex B cell precursors from the peritoneal cavity but rarely on anti-Dex precursors from the spleen.