Studies on the immunosuppressive properties of asparaginase.

The effect of asparaginase on lymphocyte kinetics and on immunological competence of normal and adrenalectomized mice has been studied. Treatment of mice with this enzyme results in lymphocytopenia and atrophy of lymph nodes, thymus and spleen. The lymph node lymphocytes from asparaginase-treated mice do not migrate normally to lymphoid organs when injected intravenously into syngeneic recipients. Splenic lymphocytes from asparaginase-treated mice induce significantly less graft-versus-host reaction when injected into F hybrids and incorporate significantly less thymidine into DNA when cultured with phytohaemagglutinin than do cells from normal mice. Skin graft rejection and the formation of antibody to sheep erythrocytes is significantly inhibited by administration of asparaginase. The immunosuppressive actions of asparaginase are manifested in adrenalectomized mice. Studies on the inhibition of phytohaemagglutinin-induced lymphocyte transformation by asparaginase suggest that asparagine depletion underlies the effect of asparaginase on lymphocytes.