Lymphocyte subsets defined by monoclonal antibodies in human pregnancy.

Using monoclonal antibodies, indirect immunofluorescence, and flow cytometry, the proportions and absolute numbers of various lymphocyte subsets in peripheral blood have been measured in normal human pregnancy. Groups of ten women were studied at 12, 28, and 36 weeks of gestation and compared with 16 nonpregnant control women. The percentage of T cells (OKT3+) was constant throughout pregnancy, and this was confirmed in three women studied serially prior to and throughout early pregnancy. A slight fall in the proportion of helper cells (OKT4+) and rise in the proportion of suppressor cells (OKT8+) was observed at 12 and 28 weeks, but these changes, and the resulting fall in helper/suppressor ratio, were not statistically significant. Absolute lymphocyte counts determined by white cell count and differential were lower during pregnancy. The absolute numbers of T cells, helper cells, suppressor cells, and Ia-bearing cells (mainly B cells) were significantly lower at 36 weeks' gestation. T cells and helper cells were significantly reduced in absolute number at 12 weeks' gestation. There was no change in the ratio of T cells to B cells at any stage of gestation. The lack of any significant change in the balance between helper and suppressor cells in peripheral blood suggests that these cells are not important in the immune adaptation to pregnancy.