Down-Regulated Expression of Perforin-Positive/CD16+ Cells in the Peripheral Blood Lymphocytes in the First Trimester of Pregnancy and Up-Regulation at the End of Pregnancy

PROBLEM: Immunophenotypic profiles of perforin (P)‐positive peripheral blood lymphocytes in the first trimester and at the term of human pregnancy were analyzed. METHOD OF STUDY: Perforin expression in peripheral blood lymphocyte subsets was measured by simultaneous detection of P (intracellular antigen) and cell‐surface antigens (CD3, CD4, CD8, CD16, and CD56) by flow cytometry in nonpregnant (NP) and pregnant women in the first trimester (FTP) and at the time of parturition (TP). RESULTS: The percentage of total P+ cells in peripheral blood compared to nonpregnant women was slightly lower in the FTP but significantly higher at TP. Perforin‐positive cells were significantly elevated in T lymphocyte subsets (CD3+P+, CD4+P\ CD8+P+) in both the FTP and TP groups, as was the percentage of CD56+P+ cells. Profound changes in the CD16+ subpopulation were found in the FTP group compared to both the NP and TP groups (a drastic decrease of CD16+P+ cells; CD16+ cells among P+ cells; P+ cells among CD16+ cells). A considerable part of CD3+ cells in both the FTP and TP groups are CD3+CD56+P+. The average fluorescence intensity (AFI) for P (a measure of P content per cell) was significantly decreased in FTP and increased in TP groups. CONCLUSIONS: The CD16 molecule is FcγRIIIA which is the only Fc receptor responsible for antibody dependent cell‐cytotoxicity (ADCC) of NK and T‐cells. In the first‐trimester human pregnancy this mechanism is severely down‐regulated compared to both the NP and TP groups.