Changes in Soluble CD4 and CD8 Proteins in Healthy Pregnant and Postpartum Women

PROBLEM: We examined physiological changes in serum levels of soluble CD4 (sCD4) and soluble CD8 (sCD8) during pregnancy and 1–12 months postpartum to study changes in the maternal immune system during and after pregnancy. METHOD: The serum concentrations of sCD4 and sCD8 were measured by enzyme immunoassay in the sera separated from blood samples withdrawn from healthy women in the 1st, 2nd, and 3rd trimesters of pregnancy and 1,4,7, and 10–12 months postpartum (n=182) and healthy non-pregnant women (n=25), and in 90 of the women, the changes in sCD4 and sCD8 were compared with changes in the number of peripheral CD4⁺ and CD8⁺ cells measured by flow cytometry. RESULTS: The serum concentration of sCD4 decreased throughout pregnancy, from the first trimester, and recovered gradually after delivery. The serum concentration of sCD8 did not change significantly during or after pregnancy compared to the concentration in the nonpregnant controls, but the concentration 1 month postpartum was significantly higher than that in the 3rd trimester. The numbers of CD4⁺ and CD8⁺ cells decreased during pregnancy but did not change significantly after delivery. Interestingly, the ratio of the serum sCD4 level to the number of CD4⁺ cells decreased and the ratio of the sCD8 level to the number of CD8⁺ cells increased in the first and second trimesters of pregnancy, but these ratios were within the normal range from the third trimester of pregnancy to 10–12 months postpartum. CONCLUSIONS: Decreases in serum sCD4 concentration and in the ratio sCD4/CD4⁺ cells, and an increase in the ratio sCD8/CD8⁺ cells may be important factors in the immunological changes that occur during pregnancy.