A-B, In vitro analyses using primary mouse uterine epithelial cells demonstrated that TNFα induces the expression of annexin V, a marker of PS presentation at the outer membrane of Rb1f/f epithelial cells but does not in Rb1d/d ones, and P4 restores TNFα-primed annexin V expression in Rb1d/d uterine epithelial cells (mean ± SEM, Student's t test). Using three lines of primary mouse epithelial cells obtained from both Rb1f/fand Rb1d/d mice, the in vivo experiments were performed three times. Each of the annexin V-positive ratios was demonstrated. Scale bar = 100μm; green signal, annexin V. 