Selective release of antibody forming cells into the blood

Cells that are actively producing antibody in the spleen are not randomly released into the blood. At comparable times after immunization, the ratio of IgM/IgG antibody-producing cells in blood differs from that in the spleen and lymph nodes. In contrast to the primary response, a heightened number of antibody-producing cells in the lymphoid tissue during the secondary response is not reflected by an increased number in the blood. The findings suggest that some immunologically active cells are selectively retained by the lymphoid tissues while newly produced antibody-forming cells are released into the blood stream.