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Biology of Reproduction, Vol 25, 77-84, Copyright © 1981 by Society for the Study of Reproduction
1 Department of Animal Science,
North Carolina Agricultural and Technical State University,
Greensboro, North Carolina 27411 The immunosuppressive effect of ovine uterine protein upon phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes was investigated in vitro. Uterine secretory protein was
collected and concentrated in sheep uterine flushings (SUF) obtained from nonpregnant and pregnant Dorset ewes on Days 4, 9, and 14 of the cycle. Varying concentrations of protein (2.5-1600
µg/ml) were added to cultures each containing 1 x 106 ovine lymphocytes and 0.6 µg of PHA.
Lymphocyte response to PHA was suppressed in cultures containing SUF protein from Day 4, 9,
and 14 nonpregnant and pregnant ewes. The regression of SUF protein concentration with lymphocyte suppression (as percent of control) for each day and reproductive stage was significant
(P<0.001). Almost complete suppression occurred with much less SUF protein (100 µg/ml) obtained on Day 14 of pregnancy than was obtained at most other times (1600 µg/ml). Ovine serum
and bovine serum albumin had no significant immunosuppressive effect. The immunosuppressive
effect of SUF protein was not mediated by cytotoxicity. It is unknown whether lymphocyte suppression observed in vitro occurs in vivo. If a parallelism exists, data from this investigation strongly suggest that the ovine uterus may possess a continual immunosuppressive substance(s) during pregnancy and the estrous cycle and that the activity
of this substance increases considerably by Day 14 of pregnancy.
Note:
ACKNOWLEDGMENTS
The author expresses his gratitude to Dr. Finnie A.
Murray for helpful suggestions during the study, Mr.
Theodore R. Bullock and Mr. Gary Riviere for their
technical assistance, and also to Ms. Pamela A. Wilson
for typing the manuscript.
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