Origin of antibody-dependent, lymphoid-cell-independent hemolytic plaques in rabbit spleen cell cultures

This report describes a phenomenon that may be a significant source of error in the data acquired from hemolytic plaque assays of lymphocyte cultures. The data show that background antibody in the normal-serum supplement of the culture medium does not actually support initiation of a vigorous primary-type plaque-forming cell (PFC) response to sheep erythrocytes (SE). Instead, the background antibody causes the development of numerous spurious lymphoid-cell-independent plaques (LCIP). In general agreement with the literature, primary-type rabbit spleen cell responses in vitro were low in culture media supplemented with fetal bovine serum, a serum which does not contain background antibodies to SE.