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

Morteta H. AL-Medhtiy, A.B.Z. Zuki, M.M. Noordin and S. Agungpriyono

American Journal of Animal and Veterinary Sciences, 2009, 4(1), 21-25.

Abstract

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.

ASCI-ID: 216-54

Fig. 1. The mean S-IgA concentrations of all uterine lavage fluids during follicular phase (0.20±0.01 µg mL^-1; 95% CI = -0.05 to -0.01) were highly significant (p<0.01) than during the luteal phase (0.17±0.002 µg mL^-1).

Fig. 1:	Mean concentration (µg mL-1) of uterine S-IgA by ELISA during follicular and luteal phase of ewe’s estrous cycle

Fig. 2:	A1, A2, A3 shows the plasma cells are localized throughout the lamina propria of the uterine horn sections. B1, B2, B3 shows it’s localized throughout the lamina propria of the oviduct sections. Stain: Methyl Green Pyronine. 40x magnification

Plasma cells population: The sections of the uterine horn and oviduct stained with Methyl Green Pyronine are showed in Fig. 2. The plasma cells were identified by their basophilic cytoplasm and an eccentrically located nucleus with the special arrangement of the heterochromatin in a characteristic of cartwheel appearance. The plasma cells were located in the basal region of the epithelium for both of anatomical regions (A1, B1). Some were presented in the stroma that supports the epithelial layer for uterine horn and oviduct (A2, B2).

Fig. 3:	Distribution of Plasma cells in the uterin horn and oviduct of reproductive tract of the ewes throughout the estrous cycle. Data are showed as the mean±SE (n = 6), (p<0.01) numbers of plasma cells within lamina propria of the oviduct and uterine horn

They were also localized between the epithelial cells of the uterine and oviduct glands (A3, B3). Present in the stroma that supports the epithelial layer for uterine horn and oviduct (A2, B2).

The plasma cells populations within the lamina propria of the uterine horns and the oviduct during follicular and luteal phases of the ewes are showed in Fig. 3. The mean number of the plasma cells was significantly higher (p<0.01) in the uterine horn during follicular phase (4.97±0.32; 95% CI = -1.9 to -0.2) compared to the luteal phase (3.87±0.30). In addition, the mean numbers of plasma cells in oviduct during follicular and luteal phase were 3.82±0.33 and 1.90±0.21, respectively. The difference was statistically significant (p<0.01; 95% CI= -2.1 to -0.5).

DISCUSSION

In this study, we examined the relationship of the uterine S-IgA and plasma cells in tissues with the influence of the estrous cycle stages in ewes. We determined that the levels of S-IgA and values of plasma cells in the reproductive tract vary at different stages of the estrous cycle. The highest levels of S-IgA and numbers of plasma cells were recorded during follicular phase (under the estrogen hormone influence), while the lowest levels occurred during the luteal phase (under the progesterone hormone influence) of estrous cycle in ewes. It was well known, that during follicular phase, the female reproductive tract at the time around of the ovulation, the secretion of cervical gland is serous-type that facilitates coming in of the spermatozoa into the uterus. During luteal phase or pregnancy, the secretions of the cervical glands become more viscous, forming a plug of thickened mucous in the orifice of the cervix, thus, preventing the coming in of sperm and microorganisms into the uterus^[13]. In sheep, one of the progesterone actions is to reduce numbers of specific populations of lymphocytes in the layers of uterine endometrium and hybridoma xenografts^[17]. It also played role by hinders rejection or enhances survival of skin allografts placed within the uterine lumen^[9]. This progesterone action may prevent immunological rejection of the newly attached fetus by the mother immune system^[8].

As ratiocination from the mentioned earlier, the female reproductive tract must be supported by the female immune system to encounter the invading of microorganism from the outer environmental during the relaxation period for the cervix, especially during the last stage of follicular phase when the female accept the male. Results of the current study are consistent with the previous researchers, where the increasing levels of uterine S-IgA and amount of plasma cell occurred during follicular phase and decreased during the luteal phase. However, the current study presents a more specific data on the amount of uterine S-IgA and plasma cells during follicular and luteal phases.

Results of the study also showed that immune system level was enhanced during the follicular phase and decreased during the luteal phase of ewes. That agrees with previous studies done in ewes, cows and mares^{[4, 5,10, 15,22,23]}. Based on the result of this study and from the previous reports, it is confirm that the difference stages of estrous cycle have different uterine immune levels in ewes. The immune system during the follicular phase under estrogen influenced is highest its levels than luteal phase under progesterone influenced in ewes.