Abstract
Summary
Immunosuppression induced in vitro by cell-free ascites fluid from mastocytoma bearing mice was examined in regards to neutralization by antiserum prepared in rabbits. Serum from rabbits immunized with mastocytoma cell extracts or culture supernatants readily neutralized ascitic fluid from tumor-bearing animals in regards to immunosuppression of normal mouse spleen cells immunized in vitro with sheep red blood cells. Rabbit serum to normal mouse immunoglobulins had no neutralizing effect on the immunosuppressive ascitic fluid. Antisera to ascites fluid resulted in a sharply defined precipitin arc after immunoelectrophoresis which could not be abolished by absorption with normal DBA/2 serum. Thus the immunosuppressive factor present in ascites fluid, as well as in cell-free extracts and culture fluids of mastocytoma cells, appeared to be antigenically distinct from mouse immunoglobulins and readily neutralized by serum from rabbits immunized with various mastocytoma preparations.
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