THE EFFECT OF ANTILYMPHOCYTE SERUM ON THE INDUCTION AND GROWTH OF TUMOR IN THE ADULT MOUSE1

Abstract

SUMMARY The effect of rabbit antimouse antilymphocyte serum (RAMLS) on the growth of a transplantable mouse mammary tumor and its ability to influence the incidence of methylcholanthrene-induced tumors was studied in the adult mouse. RAMLS treatment of mice injected with tumor cells markedly accelerated tumor growth when tumor was transferred across the H-1 and H-2 histocompatibility barriers. It also eliminated preexisting sensitization resulting in death from tumor in immune mice. In addition, RAMLS increased the incidence and shortened the latent period of methylcholanthrene-induced sarcomas. Absorption of RAMLS with viable tumor cells did not decrease its ability to accelerate tumor growth; absorption of RAMLS with lymphocytes essentially erased this capability. Tumor cells incubated in vitro with RAMLS retained the capability of killing the host when injected into normal mice. The observed effects of RAMLS appear to be secondary to its immunosuppressive properties rather than to enhancement. The marked ability of RAMLS to influence tumor growth is in part related to the absence of an inhibitor of tumor cell viability in RAMLS.