Studies on the Immunosuppressive Effects of Anti-thymic and Anti-bursal Lymphocyte Sera

Abstract

Rabbit anti-thymic and anti-bursal lymphocyte sera (hereafter abbreviated to RATLS and RABLS, respectively) were examined for immunosuppressive effect on the hemolytic plaque-forming cells (PFC) and rosette-forming cells (RFC) in the spleen, and on experimental allergic encephalomyelitis (EAE) in chickens. The results obtained are as follows:1) RATLS anb RABLS had a high lymphoagglutinating activity on the thymic and bursal lymphocytes, respectively. In addition, a cross-reaction was observed between both anti-lymphocyte sera. This suggests that the thymic and bursal lymphocytes may have common antigen(s) in addition to the respective specific antigen(s) on the surface of the cell.2) Repeated administration of RATLS caused a more remarkable fall in lymphocyte count of the peripheral blood than that of RABLS. Furthermore, severe depletion of lymphocytes in the white pulp of the spleen was a characteristic change caused by RATLS, and a slight decrease in lymphocytes and pyroninophilic cells and the appearance of ill-defined germinal centers were ones induced by RABLS.3) In the primary response, when RABLS was injected daily for five days following the sensitization with sheep erythrocytes, there was a marked decrease in the number of PFC and RFC in the spleen. In contrast, such a suppression by RABLS was not so marked in the secondary response in previously immunized birds. On the other hand, RATLS was found to have a weak suppressive effect only in the primary response.4) The occurrence of EAE and the delayed-type hypersensitivity (wattle test) to the encephalitogenic basic protein of myelin were suppressed remarkably by the repeated injection of RATLS, but much less remarkably by the repeated administration of RABLS.From the findings obtained, it was ascertained that RATLS exerted a suppressive effect selectively on the cell-mediated immune reaction, and that RABLS did such an effect on the humoral antibody production. Therefore, both anti-lymphocyte sera were proved to have a considerably high selective activity in their immunosuppression.