Interference with the Cytolytic Activity of Interleukin-2-Treated Lymphocytes by Bovine

Bovine uterine luminal protein (ULP) components ( 4 x 106 and 21 000 Mr) were obtained from uterine flushings on Day 17 of pregnancy. Experiments were conducted to determine the capability of these components to interfere with the cytolytic activity of interleukin-2 (IL-2)-treated peripheral blood lymphocytes (PBL), designated LAK (lymphokine-activated killer) cells, upon K-562 tumor cells. Proteins (10-100 ixg) were added at the onset of a 5-day culture period to wells containing PBL (3 x 106) + bovine recombinant IL-2 (12 000 IU). After culture, percentage cytotoxicity (Cyt) was assessed by the 51Cr release assay at 4 and 22 h of incubation for ratios (5:1-200:1) of LAK:K-562 cells. Percentage Cyt was affected (p < 0.0001) by time, ratio, protein treatment, and all two-way interactions. Although trends were apparent, neither ULP component affected (p> 0.05) percentage Cyt at 4 h. By 22 h of incubation, mean percentage Cyt values for the 4 x 106 and 21 000 Mr, components at effector:target cell ratios of 150:1 (p < 0.002) and 200:1 (p < 0.0001) were less than percentages for LAK cells alone. BSA and serum protein (control preparations) each failed (p> 0.05) to affect percentage Cyt. In conclusion, both ULP components interfered with the cytolytic activity of LAK cells, presumably by the suppression of LAK cell generation