Lytic activity of lung and spleen lymphocytes against MADB106 tumor. The influence of B cells on tumor lysis was determined by comparing the percentage lysis of MADB106 tumor cells in the presence or absence of B cells. Total lymphocytes or lymphocytes depleted of B cells from lung and spleen tissues were incubated with viable fluorescently-labeled MADB106 tumor cells for 90 min. Tumor lysis was measured by propidium iodine (PI) staining of labeled MADB106 tumor cells. Percentage lysis was expressed as the percentage of fluorescent positive tumor cells staining positive for PI in the presence of lymphocyte cultures minus the percentage of PI-labeled tumor cells in the absence of lymphocyte cultures. The data shown were analyzed by analysis of variance (ANOVA). The main effect of E:T ratio was significant in both analyses (lung: F = 18.6, P < 0.001; spleen: F = 328.6, P < 0.001), thus verifying that killing increased as the E:T ratio increased. Separate analyses were conducted for lung and for spleen lymphocytes, with or without B cells, present in the assay [each a two-way ANOVA − lymphocyte composition (total or B cells removed) x E:T ratios (12:5, 25, 50, 100:1)]. In both analyses, the main effect of lymphocyte composition was statistically significant (lung: F = 162.0, P < 0.001; spleen: F = 31.7, P < 0.02). Data is expressed as the mean ± S.E. (n = 3) at a given effector:target (E:T) ratio.