Immunosuppresive Effects of Steroid Hormone on Subpopulation of Lymphocytes in Mouse and Man

The in vivo effects ot a single administration of prednisolon on T and B lymphocytes in different immune organs of mouse and man were investigated. In mouse, with both populations, two effects with different kinetics which appeared early and late after drug-administration were observed. As early as few hours after drug-administration, T and B lymphocytes in peripheral blood and spleen decreased in parallel and those in bone marrow and lymph nodes inversely increased. Both changes of T and B lymphocytes continued for several hours and reversed within 24 hours. For the following two days, both cell levels were relatively constant and thereafter decreased prominently in all immune organs. After going down to the minimum levels on day 5th or 7th, they increased and reached the normal levels on day 10th or 12th. Thus, ths late effect may be a result of exahustion of lymphoid cells due to the inhibition of proliferation of their precursors. For the mechanism involved in early effect, it was suggested that prednisolon-treatment may elicit a constriction of peripheral vessels and spleen mediated by its transient response to a-adrenergic stimulus, and result in an expulsion of T and B cells out of circulation into bone marrow and lymph nodes. Immunization with sheep erythrocytes of mice at either early or late phase after drug-administration resulted in a decreased production of antibody-forming cells, though the early effect was much less and variable. Furthermore, the high dsoe of a single administration of prednisolon induced early and late effects, but the low dose induced only early effect. In man, changes of lymphocytes after drug-administration was observed only at early phase, probably because of the low dose of a prednisolon-administration. The different dose-dependency of early and late effect is quite interesting in addition to their distinct kinetics