Distribution of T cells in the endometrium of the mare 6 and 48 h after insemination

In order to study the T-cell response after the introduction of semen into the uterine cavity, the distribution of helper T cells (CD4+) and cytotoxic /suppressor T cells (CD8+) was examined immunohistochemically in endometria l biopsy specimens. Endometrial tissue samples were obtained from 19 gynaec ologically healthy mares during oestrus, both before and 6 or 48 h after de position of a single dose of neat stallion semen. An increase (p = 0.04) in the numbers of helper T cells (CD4+) was observed at 6 h after inseminatio n; thereafter the number of CD4+ cells decreased to pre-insemination values by 48 h after insemination. No significant variations in numbers of CD8+ c ells were recorded either 6 or 48 h after insemination. There seems to be a n early (6 h), recruitment of helper T cells into the equine endometrium af ter semen deposition, which might be related to the activation of the endom etritis-like reaction seen as part of the equine uterine immune defence sys tem during oestrus.