Fate of H3-Thymidine-Labeled Spleen Cells in in Vivo Cultures during Secondary Antibody Response

Labeled donor spleen cells colonized preferentially in the hematopoietic tissues of heavily irradiated, isologous recipient mice. More labeled cells were detected in the spleen and bone marrow than in the lymph node and thymus, and more were seen in the latter tissues than in the liver, lung, and small intestine. These results suggest that spleen cells have a “homing instinct” in irradiated recipients. Studies on the proliferative capacity of donor-labeled lymphoidal cells in the recipient spleen (H3T-Index and mean grain count/cell) indicate that the maximum mean generation time of these cells can be shortened 2-fold when stimulated by an antigen from ∼24 to ∼12 hr. This accelerated rate of proliferation occurs 2 days before the appearance of antibody in the circulation. The results, furthermore, suggest that mature plasma cells, following an antigenic stimulation, are derived from three to four cellular divisions.