Ultrastructural study of uterine natural killer cells found in pregnant, interleukin-2 receptor beta-chain overexpressed transgenic mice

We previously reported that all fetuses died or were resorbed on day 12 of pregnancy (Day 1=the day of plug) in interleuldn-2 (IL-2) receptor Beta-chain overexpressed transgenic (Tg2Rbeta) mice. In this study, to clarify the role of uterine natural killer (uNK) cells in pregnancy, the ultrastructure of Tg2Rbeta mouse uNK cells was analyzed using a transmission electron microscope, uNK cells and their granules on day 10 of pregnancy were larger in Tg2Rbeta mice than control mice, indicating that differentiation of uNK cells in Tg2Rbata mice progressed rapidly. Additionally, the granules of uNK cells in Tg2Rbeta mice on day 10 of pregnancy had an irregular morphology. The multivesicular regions were present in the cap structure of these granules, suggesting that the uNK cells of the Tg2Rbeta mice had cytotoxic activity.