Endometrial distribution of bovine immune cells in relation to days to conception after parturition

Abstract

In dairy cows, the processes involved in the resolution of uterine inflammation during thepostpartum are closely related to improved fertility during the subsequent lactation period. Littleis known, however, about the role and distribution of endometrial immune cell populationsduring the pre-implantation period. This study was aimed to analyze the endometrial distributionof several mononuclear immune cells (T cells, γδ T cells, B cells and macrophages) in healthydairy cows during the postpartum, beyond the transition period, looking for its possible association with the parturition-conception interval (PCI) and delayed conception. The quantification of immune cells was evaluated by immunohistochemistry (IHC), and the expression of hormone receptors in immune cells was evaluated by double IHC. Dairy cows were grouped according to their PCI: PCI shorter than or equal to 90 DIM (PCI≤90), PCI between 90 and 120 DIM (PCI90–120), and PCI greater than 150 DIM (PCI≥150). The distribution of endometrial mononuclear immune cells was analyzed by a Generalized Linear Model, and the association of the distribution of mononuclear immune cells with delayed conception was evaluated with a Kaplan-Meier test. The cows from the PCI90–120 group showed the highest number of endometrial macrophages, and a lower number of B cells than the PCI≤90 group. Results also showed an association between the lower number of B cells in the endometrium during the pre-implantation period and earlier conception. Also, the present findings indicates that ESR and PR are expressed in the endometrial MØ, T cells, γδ T cells and B cells.