IMMUNOHISTOCHEMICAL STUDY OF IMMUNE CELLS IN THE BOVINE ENDOMETRIUM AT DIFFERENT STAGES OF THE ESTROUS-CYCLE

Normal uteri were collected from 34 maiden heifers at slaughter and th eir stage of the oestrous cycle was determined from the ovarian struct ures. Cells expressing major histocompatibility complex (MHC) class II were widely distributed in the epithelium and lamina propria of the e ndometrium and were the most abundant population studied. The expressi on of MHC class II increased in the endometrium during the follicular phase of the cycle. Macrophages occurred throughout the stratum compac tum and stratum spongiosum and their density did not appear to vary wi th the stage of the cycle. CD4+ cells were found mainly in the stratum spongiosum, whereas CD8+ cells were present mainly within the luminal and glandular epithelia and in the stratum compactum. The density of the populations of CD4+ and CD8+ cells increased markedly during the m id-to-late luteal and follicular phases, respectively, of the cycle. I n the endometrium lymphoid aggregates were observed only rarely and no B cells were identified in any of the heifers.