Fig. 5.

Possible model of immune-related gene expressions and their interactions during periods covering days 13, 19 and 25, while the equine conceptus goes through three stages of development; migration (day 13, Upper), fixation (day 19, Middle), and attachment (day 25, Lower) to the uterine endometrium. Intrauterine migration induces endometrial IL-15, resulting in NK cell recruitment. These uNK cells produce GZMB and induce other immune-related gene expressions at the phase of conceptus fixation. As the capsule subsides and conceptus attachment proceeds, Th1 and Th2 cells are recruited into the attachment area of the endometrium. These sequential gene expressions may be required for equine pregnancy to proceed.