Immunodeficiency following splenectomy in the early postimmunization period.

Splenectomy is associated with an increased risk of serious infection with encapsulated micro-organisms in a small number of individuals. The immunological defects in this state are unclear. We have investigated in rabbits the effect of splenectomy, before and after primary immunization with a specific antigen (sheep erythrocytes) similar in structure to the pneumococcal capsular antigen, on the organ localization of antibody forming cells and the long-lived memory cells. Antibody forming cell and memory cell assays were performed at intervals up to day 270 after primary immunization. Antibody titres following secondary immunization were also measured. The results show that the major site of antibody forming cells is in the spleen following primary immunization of the untreated rabbit and that antibody forming cells subsequently migrate to the lymph nodes and thymus. On the other hand, in rabbits splenectomized before primary immunization the major site of the antibody forming cells is the peripheral lymph nodes. These rabbits also gave good secondary immune responses. However, splenectomy 40 days after primary immunization results in a poor secondary immune response, indicating that essentially all the antibody forming cells following primary immunization were localized in the spleen at the time of splenectomy.