Lymphocyte subsets in the endometrium of genitally normal mares and mares susceptible to endometritis.

This research article investigates the presence and distribution of certain cells and lymphocyte subpopulations in the endometrium (lining of the uterus) of mares (female horses). The researchers compare these findings between healthy mares and mares prone to endometritis, an inflammation of the endometrium. They find that regardless of their endometritis susceptibility, mares have differing amounts and types of cells in varying parts of the endometrium. However, mares susceptible to endometritis have significantly higher densities of certain types of lymphocytes.

Research Background

• The research studies the presence and distribution of lymphocyte subpopulations and MHC Class II positive cells in the endometrium of mares.
• The study compares data from genitally healthy mares and mares susceptible to endometritis, a uterine inflammatory condition.

Findings in Genitally Normal Mares

• Greater numbers of MHC Class II positive cells were found in the epithelium (surface layer) and stratum compactum (part of the endometrial stroma) of healthy mares during oestrus (a phase of the reproductive cycle) compared to dioestrus (another phase of the reproductive cycle).
• More CD4+ and CD8+ lymphocytes (a type of white blood cell) were found in the stratum compactum compared to the stratum spongiosum (another part of the endometrial stroma).
• More CD4+ lymphocytes than CD8+ lymphocytes were present in the stratum compactum, but roughly equal numbers were found in the stratum spongiosum and in lymphoid aggregates (clusters of immune cells).
• Occasionally CD4+ and CD8+ cells were found in the luminal (innermost) and glandular epithelium (layer of glandular cells).
• B cells (another type of white blood cell) were rarely present in the endometrium and not observed in the epithelium.
• The quantities of T and B cells did not seem to be affected by the stage of the mare’s reproductive cycle.

Findings in Mares Susceptible to Endometritis

• Densities of CD4+, CD8+, and B cells were significantly increased in mares prone to endometritis.
• Large aggregates of lymphoid cells, containing about twice as many CD4+ cells compared to CD8+ cells, were present in these mares’ endometrium.
• All three subclasses of lymphocytes were occasionally found in the luminal and glandular epithelium.

Research Implications

• The results indicate that the distribution and quantity of certain cells and lymphocyte subpopulations differ between the endometrium of healthy mares and those susceptible to endometritis.
• These differing profiles can potentially provide insight into the immune responses of the mare’s endometrium and how it might be connected to disease susceptibility.
• Understanding these patterns could contribute valuable knowledge for treatment strategies and potentially to the prevention of endometritis in mares.