Demonstration of tumor-associated immunity with a leukocyte adherence inhibition (LAI) assay.

A modification of the leukocyte adherence inhibition (LAI) assay of Halliday was used to search for immune reactions against tumor-associated antigens of mouse tumors as well as against embryonic antigens in such neoplasms. Soluble antigen extracts were prepared from transplanted (BALB/c) methylcholanthrene-induced sarcomas and carcinomas, from normal BALB/c embryos taken at 14-18 days' gestation and from kidneys and livers of adult BALB/c mice. Peritoneal cells (PC) from mice immunized against syngeneic tumors gave leukocyte adherence inhibition more commonly when exposed to antigens prepared from the same tumor than did PC from normal (untreated) mice or from mice immunized against a different tumor. However, different tumor antigen preparations varied vastly in their ability to give specific adherence inhibition; some preparations consistently gave a high tumor-specific inhibition, while others did not. This may explain why the degree of reactivity observed was low and its tumor specificity not absolute when data obtained with all different antigen extracts were pooled. PC from multiparous mice gave adherence inhibition when exposed to antigenic extracts from syngenic mouse embryos or from tumors, as compared to PC from virgin mice exposed to the same extracts. Furthermore, PC from tumor-immunized mice reacted more commonly against antigen extracts from mouse embryos than did peritoneal cells from normal untreated mice. Adherence inhibition was not observed when PC from tumor-immunized or multiparous mice were exposed to antigen extracts from adult syngeneic livers or kidneys.