Idiotypic lymphocytes in the rabbit: occurrence and nature of idiotypic lymphocytes in normal and hyperimmunized rabbits.

Rabbits were hyperimmunized with Micrococcus Pysodeicticus, leading to homogeneous antibody responses. Peripheral blood lymphocytes were taken from the rabbits before and monthly (during 3 months) after the start of the immunization. The cells were stored frozen. Lymphocytes were tested with anti-idiotypic conjugates for the presence of surface idiotypic structures. The nature of the idiotype-positive cells was determined with respect to the presence of IgM or T-cell antigenic determinants on their surface. A sharp rise and fall in the percentage of idiotypic lymphocytes was found, ranging between 1/40,000 and 1/1,000. Initially almost all idiotypic lymphocytes were IgM-positive. In the blood taken 2 months after the start of the immunization 20% of the idiotypic cells belonged to the T-cell population and 10% were negative for both IgM and T-cell antigenic determinants.