A kinetic study of antibody producing cells in the spleen of mice immunized intravenously with sheep erythrocytes.

The number of antibody producing cells, i.e. rosette forming cells (RFC) has been studied in the spleen of mice injected intravenously with a full immunizing dose of sheep RBC. The spleen of a non-immunized mouse contains a background of about 70,000 RFC (normal RFC), which do not appear to be the target cells' for antigens of sheep RBC. Our findings suggest that the spleen of a mouse contains about 4000 target cells' which initiate the immune response to sheep RBC. In the primary response, the rise of RFC is exponential for about 96 hours with a doubling time of 13 hours involving seven to eight consecutive doubling periods. The peak value of RFC is 1·6 × 10 per spleen. In the secondary response, the doubling time of RFC is 6–7 hours. The exponential rise lasts 72 hours and includes nine to eleven doubling periods leading to a peak of 3·5 × 10 RFC/spleen. Adjuvant in the primary response leaves the doubling time of RFC unaltered but prolongs the exponential rise until the 120th hour leading to a peak of 6·3 × 10 RFC/spleen after ten doubling periods. The effects of priming and adjuvant are not fully additive.