SUMMARYThe hematological and the immunological studies of antincutrophilicserum(ANS),and antilymphocytic serum(ALS) show remarkable agreement. Thus,ANS produces its significant effects on stabs and neytrophils whereas ATS has a distinct effect on stabs and neutriphils and, also a very distinct effect on the lymphcyts. ALS produces a significant reduction in blood and marrow neutrophils. Precipitating antibodies to neutrophil antigens are present in both ANS and ATS. No precipitating antibodies have been demonstrable in and about Hassall's corpuseles by immunofluorescent technique.The findings may be of importance in the interpretation of certain experimental results dealing with immunosuppression by means of antisera for white blood cells.