Significance of human neutrophil antigen-2a (NB1) expression and neutrophil number in pregnancy.

Background: Expression of human neutrophil antigen-2a (HNA-2a) is greater in women than in men. The size of the HNA-2a-positive neutrophil population increases with pregnancy.

Study Design And Methods: T he relationship between HNA-2a expression on neutrophils and monocytes, and their relative numbers, was investigated. HNA-2a expression shown as the size of the HNA-2a-positive cell population and the fluorescence intensity on the cells was analyzed using flow cytometry. This investigation was done among 165 pregnant women during pregnancy and postpartum.

Results: In normal pregnancy, numbers of neutrophils and monocytes changed in relation to HNA-2a expression. HNA-2a was also expressed intensively on monocytes from some pregnant women in the first and second trimesters. HNA-2a expression and the number of cells markedly decreased postpartum. In threatened premature labor, the number of neutrophils decreased earlier than in normal pregnancy.

Conclusion: HNA-2a expression may increase soon after fertilization. In this study, the results indicate that the change in the number of neutrophils and monocytes is related to HNA-2a expression.