Both the uterus and oviduct are functionally adapted to facilitate sperm transport, oocyte fertilization, embryonic/fetal development, and deliver a calf. However, the mucosa of the uterus and oviduct is exposed to ascending infections at coitus, during pregnancy, and after parturition. Therefore, the mucosal immune system of the uterus and oviduct should exhibit a large degree of flexibility to potentially regulate maternal immune reactions to allogeneic spermatozoa and semi-allogeneic embryos without hindering the effective immune defense responses against infectious agents (Ellington, 1991; Yaniz et al., 2000; Bauersachs and Wolf, 2013).

Immunologically, sperm are allogeneic to the maternal immune system (Gaunt, 1983; Lander et al., 1990). Therefore, once sperm is deposited into the uterus during artificial insemination (AI), a sequence of cellular dynamics and immunological inflammatory reactions toward sperm is anticipated. These inflammatory responses are regarded as the rapid and transient leukocytic infiltration, mostly polymorphonuclear neutrophils...