The mitotic activity of, and antibody production by, sensitized lymphocytes quantified after transfer into irradiated recipients.

Adult thymectomized, irradiated CBA mice were reconstituted with bone marrow and thymus grafts derived from congenic strains differing in immunoglobulin allotype. After challenge with heterologous erythrocytes the allotype of the antibody secreted by the chimaeric spleen cells was the same as that of the bone marrow donor. When mixtures of immune and non-immune cells from the two congenic strains were transferred to irradiated recipients, a preponderance of the immune-donor cells was found dividing in the recipients' spleen 3 days after challenge with the immunizing antigen, and the allotype of the antibody-producing cells 7 days after challenge was almost entirely of immune-donor derivation. Further quantitative studies on the number of mitotically reactive cells observed after immunization with heterologous erythrocytes indicate that after primary and secondary challenge the mitotic activity of these cells is increased respectively four and eight times relative to that found in unsensitized cells.