Plasma Cells and their Precursors IV. Cross-reacting and Non-cross-reacting, Sheep Erythrocyte Lysing IgG Antibody Clones Induced in Rabbits Immunized with Rat- and Chicken-Erythrocytes

Rabbits were i.v. immunized with rat erythrocytes or chicken erythrocytes. The sera were investigated using the IEF technique. A number of the RRBC immunized animals and a high proportion of the CRBC immunized animals contained SRBC-lysing IgG antibody clones in addition to apparently normal anti-RRBC or anti-CRBC antibodies. Intravenous immunization with RRBC, followed by immunization with CRBC, yielded clones of SRBC-lysing IgG antibodies in almost every rabbit tested. By varying the interval between the RRBC- and CRBC injections, we established that the time needed for the RRBCinduced production of the responsible SRBC-specific IgG AFCP is approximately 5 days. These cells show an average functional half-life of 75 days. At least some of the RRBC- and CRBC-evoked SRBC-lysing IgG antibody clones are incapable of lysing either RRBC or CRBC. We suggest that the production of cross-reactive and non-cross-reactive, hetero-specific AFCP provides a natural explanation for the availability of preexistent AFCP responsible for the presence of the -early phase- of the IgG antibody response to several antigens.