Immunologic factors contributing to the initiation of labor--lymphocyte reactivity in term labor and threatened preterm delivery.

To obtain data on the immunologic events during labor, we investigated cytotoxic activity, progesterone-prostaglandin F2 alpha and prostaglandin E2 sensitivity of the lymphocytes in late pregnancy at early and late stages of labor and in the puerperium. In an attempt to investigate common determinants between the behavior of lymphocytes during labor and threatened preterm delivery, the same parameters of lymphocytes obtained from women with threatened preterm delivery were tested in parallel. At the beginning of labor, cytotoxic activity of the lymphocytes significantly increased and remained at a high level till the end of labor. A negative correlation (r = -0.803) was found between the increase of cytotoxicity and the duration of labor. High progesterone sensitivity of pregnancy lymphocytes decreased while low sensitivity to prostaglandin E2 increased during labor. Sensitivity of the lymphocytes to prostaglandin F2 alpha was similar in all of the groups examined. Except for prostaglandin E2 sensitivity all parameters of the lymphocytes obtained from women with threatened preterm delivery were similar to those of lymphocytes obtained during labor.