Suppression of Interleukin-2-Mediated T-Lymphocyte Blastogenesis by Ovine Uterine Luminal Protein1

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Abstract
Ovine uterine luminal protein (ULP) obtained from ewes on Day 14 of pregnancy suppressed blastogenesis of interleukin-2 (IL-2)-dependent T-lymphocytes. Varying concentrations of ULP (4 to 96 .mu.g/ml) followed by a 1:4 dilution of human IL-2 suppressed (p<0.001) IL-2 blastogenesis of IL-2-dependent T-lymphocytes with mean percentage of control values ranging from 55.3 to 34.5% (44.7 to 65.5% suppression, respectively). For two experiments, IL-2 was added at varying times (zero to 4 h) after the addition of ULP to cultures. Suppression was independent of IL-2 addition time. Mean (.+-. SEM) percentage of control values for combined time periods for 40 and 120 .mu.g ULP/ml were 43.3 .+-. 1.0 and 27.8 .+-. 1.9%, respectively. In another experiment, additional IL-2 (1:2 vs. 1:4 dilution) reduced (p<0.01) the immunosuppressive effect of ULP. Sephacryl S-200 chromatography of ULP and the phytohemagglutinin (PHA) blastogenesis assay revealed significant immunosuppressive activity for Fractions I (.gtoreq. 248,000 Mr), III (70,000 Mr) and V (14,000 Mr). These fractions also suppressed (p<0.001) IL-2-mediated blastogenesis of T-lymphocytes. Results indicate that immunosuppression of PHA-treated lymhocytes was associated with an alteration of the IL-2 system.