Inhibition of in vitro plaque formation by large granular lymphocyte leukemia cells from F344 rats.

The effect of large granular lymphocyte leukemia on B lymphocyte function was studied by determining the number of plaques formed in an in vitro hemolytic plaque assay. Leukemia cells inhibited plaque formation by normal splenic lymphocytes in a logarithmic, dose-dependent manner. At the highest leukemia cell concentrations, spleen cell suspensions made 50% fewer plaques. Plaque forming responses were very sensitive to duration of preincubation time in all assays. The number of plaques formed decreased markedly if incubated 2 hr before the assay was performed. Incubation of the cells at 56 degrees C for 8 min did not alter the inhibitory activity but pretreatment with 0.01% trypsin did. Supernatant fluids from leukemia cell suspensions did not inhibit plaque formation. These data suggest that diffuse infiltration of lymphoid tissues by leukemia cells may interfere with some normal lymphocyte functions. Although leukemia cells inhibited splenic B lymphocyte function, leukemic rats did not have hypogammaglobulinemia.