Secretary IgA Concentrations and plasma Cell Count Changes Associated with the Estrous Cycle in Ewes

Problems statement: The level of uterine Secretory-IgA (S-IgA) and numbers of plasma cells was measured to observe the differences between two stages of estrous cycle (follicular and luteal phase) in the healthy cycling non pregnant ewes. Approach: Twelve ewes were used in this study and they were divided into two groups of 6 animals each according to the stages of estrous cycle. All ewes were subjected to estrous synchronization and allowed to undergo one natural estrous cycle after the removal of the sponge. All animals were then slaughtered at the end of the experiment. The uterine mucus was collected by flushing with a mixture of protease inhibitor cocktail in distilled water. For both stages, the level of uterine S-IgA was quantified by using ELISA and Methyl Green Pyronine staining was used to observe the plasma cell in the tissues of the uterine horn and oviduct of ewe's genital tract. Results: The results were analyzed by independent sample t-test and presented as mean±SEM. This study showed the relationship of the estrous cycle stages to uterine S-IgA concentration (μg mL^-1) and populations of plasma cell in the healthy non-pregnant cycling ewes. The concentration (μg mL^-1) of S-IgA (0.20±0.01) in the follicular phase was highly significant (p<0.01) as compared with the luteal phase (0.17±0.002). In addition, the populations of the plasma cells were significantly higher (p<0.01) in the uterine horn (4.97±0.32) and oviduct (3.82±0.33) during follicular phase compared to the luteal phase (3.87 ±0.30) and (1.90±0.21), respectively. Conclusion: The main reason for the immunosuppression during the luteal phase did not fully justified, especially with the presence of potential acquired infection during coitus in the follicular phase and at the same time immune system should decrease accordingly to prevent newly attached fetus rejection by the mother immune system.