THE ROLE OF IMMUNE CELLS IN THE SOW ENDOMETRIUM DURING DIFFERENT STAGES OF THE OESTROUS CYCLE AND EARLY PREGNANCY

Abstract

Approximately 30%(range 13-49%) of sows are culled due to fertility disturbances. Reproductive failure on farms are due to anoestrus, repeat breeding (regular and irregular return to oestrus), negative pregnancy diagnosis, abortion or failure to farrow. Reproductive problems are often difficult to diagnose. As a diagnostic tool, post-mortem examination (i.e. macroscopically and histologically) of the reproductive organs is useful when sows with reproductive failure are culled. The present review provides information about the distribution of immune cells, both in non-inseminated and inseminated pregnant sows endometrium, in order to be able to differentiate a physiological distribution of immune cells from pathological conditions. In non-inseminated
sows, the infiltration and distribution of immune cells in the endometrium varied throughout the oestrous cycle, which suggests direct or indirect hormonal control. In both non-inseminated and inseminated pregnant sows, the distribution of T lymphocyte subpopulations indicate that the helper and cytotoxic functions of the immune
system have primary locations in different tissue layers. In pre-ovulatory, inseminated and pregnant sows, the immunomodulation illustrated by the distribution of leukocytes, CD2+, CD4+, CD8+ and MHC class II expressing cells, at the attachment sites on day 19, i.e. the low numbers on the surface epithelium and high numbers in the
subepithelial layer, shows that the porcine trophoblast may influence the endometrium in developing the conditions required for embryonic attachment and survival