MHC CLASS-II POSITIVE CELLS AND T-CELLS IN THE EQUINE ENDOMETRIUM THROUGHOUT THE ESTROUS-CYCLE

The quantity and distribution of MHC Class II positive cells and T cells in the equine endometrium was investigated throughout the oestrous cycle. Significantly more MHC Class II positive cells were detected in the stratum compactum and stratum spongiosum of endometria from naturally cycling mares during the follicular than during the luteal phase of the oestrous cycle. Significantly more T cells were also detected in the stratum compactum, but not stratum spongiosum, of these mares during the follicular phase. Furthermore, there was a marked increase in the number of MHC Class II positive cells and T cells in the endometria of ovariectomised mares treated with oestradiol compared with progesterone. An increase in the expression of MHC Class II antigen by endometrial epithelial cells was also observed in mares treated with oestradiol and in some naturally cycling mares during the follicular phase.