Donkey endometrium: Characterization of resident immune cells

The Burro de Miranda is an endangered donkey breed. The dynamics of the immune system of the donkey's reproductive tract are essential to manage the fertility of these animals for the improvement and survival of the species. In mares, high numbers of immune cells infiltrating the endometrium promote endometrosis, which is still to be confirmed in jennies. Uterine biopsies of 32 jennies were evaluated based on the Kenney and Doig grading system used in mares. Hematoxylin and eosin stain was used to assess the infiltration and distribution of neutrophils and eosinophils. Macrophage and B and T lymphocytes endometrial distribution was conducted through immunohistochemistry. T lymphocytes were the most predominant cells in jenny endometrium, macrophages being the second. T lymphocytes were also found in the superficial and glandular epithelium. Eosinophils, neutrophils and B lymphocytes were the least common cells. No differences were found in the inflammatory infiltrate compared to the different endometrosis grades (IIA, IIB and III). This study mapped the immune cells in jenny's endometrium, providing core valuable information for additional immunological and reproductive studies in this species. It also highlighted significant differences in endometrial immune cell distribution between the jenny and the mare during estrus and diestrus, supporting the need to develop of a more suitable scoring system than the current Kenney and Doig categorization to assess the morphology and clinical feature of jenny's endometrium.