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Ovine uterine cells that represented Day 14 cyclic and pregnant endometrium were fractionated with Percoll and evaluated for suppression of cocultured phytohemagglutinin (PHA)-induced peripheral blood lymphocyte (PBL) proliferation and for the presence of T-lymphocyte markers. Uterine cells were then evaluated for suppressor activity following the depletion of conventional lymphocyte classes (i.e., T-, B-, and NK-like) with complement + antibody treatment. In addition, supernatant (derived from cultured uterine cells) was tested for transforming growth factor beta (TGFbeta) activity using neutralization antibodies to TGFbeta. Fractionated uterine cells (density range of 1.002-1.056 g/ml) from cyclic and pregnant ewes suppressed PHA-induced proliferation of PBL, and the majority (69.5%) of these cells were < or = 5.2 microm in diameter. Percentages of CD5+, CD4+, and CD8+ lymphocytes recovered from endometrial curettage were less for cells in this density range than for cells with greater densities. Uterine cells released suppressor factor(s) into the culture medium (supernatant); however, suppressor activity was unaffected by either anti-TGFbeta or complement + antibody treatment. In conclusion, low-density uterine cells from Day 14 cyclic and pregnant ewes suppressed the proliferation of cocultured PBL and released a suppressor factor(s) into the medium that did not exhibit TGFbeta activity. It is unlikely that the suppressor cells comprise conventional T-, B-, or NK-like lymphocyte lineages.

Bovine uterine luminal protein (ULP) components (> or = 4 x 10(6) and 21,000 M(r)) 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 micrograms) were added at the onset of a 5-day culture period to wells containing PBL (3 x 10(6) + 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 > or = 4 x 10(6) and 21,000 M(r) 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.