Study on the human natural killer (NK) cell activity in the normal first pregnancy, post partum and hydatidiform mole

Abstract

Previous studies in mice, had revealed an increase in levels of null cells in the maternal lymphoid organs and peripheral blood during the first pregnancy. Several investigators had suggested an alteration of NK cell in human pregnancy; however, controversies still exist. In the present studies, groups of the first, second and third trimester of primigravidous and postpartum women as well as hydatidiform mole patients were studied. The conventional cytotoxic assay of radioactive chromium-51 release was done. The number of NK cells was enumerated as large granular lymphocytes (LGL) from Giemsa stained blood films. The results showed a slightly increased in NK cell activity during the first and second trimesters. Significantly increased NK cell activity was observed in the group of third trimester subjects. After parturition, NK cell activity dropped to the same levels as observed in normal healthy female controls. The alterations of NK cell function and possible LGL level during pregnancy suggest a preferential recruitment of active NK cells from the circulating blood cells. Nevertheless, such alteration should be harmless to both fetus and mother. Preliminary studies of NK cells in patients with hydatidiform mole indicated that the NK cell activity of primigravidous patients was slightly depressed, whereas NK cell activity of the multigravidous patients was the same as or slightly increased from normal primigravidous pregnant. It is premature to draw any conclusion, that there is a negative correlation of NK cell activity against gestation time.