The influence of parturition on peripheral blood mononuclear phagocyte subpopulations in pregnant women.

Mononuclear phagocytes (MPs) from human peripheral blood were separated on discontinuous Percoll gradients into two subpopulations. A high density population was isolated which contained less mature MPs, while the MPs in the low density population were more mature cells. The proportion of high density MPs was found to increase sharply in conjunction with the peripheral blood monocytosis associated with parturition in women. The data show that there is a measurable response in the circulating MP pool to this acute inflammatory stimulus and that this response is manifested as an increase in absolute numbers of both total and high density MPs. No significant change was found in the number of low density MPs.