Application of the indirect tube LAI assay in the study of cell-mediated immunity in rats immunized with B77 tumor cells.

The indirect tube LAI (leukocyte adherence inhibition) test has revealed that peripheral blood lymphocytes of rats of the inbred Lewis strain immunized with liver B77 tumor cells incubated in the presence of a specific tumor extract, release a factor into the culture medium that inhibits adherence of normal syngeneic peritoneal cells. Supernatants in which lymphocytes of healthy - control animals had been incubated in the presence of the same extract (B77), or lymphocytes of immunized donors incubated in the presence of another type of tumor extract (MC-1) were devoid of such a property. This soluble factor was found in the supernatants only after 20 hours of incubation of sensibilized lymphocytes with a specific tumor extract. Th percentage of adhering cells decreased in dependence on the concentration of the soluble factor. The results are discussed in connection with questions relevant to the mechanism of LAI reactivity and the application of this phenomenon in studies on cell immunity.