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 pre gnancy were analyzed. METHOD OF STUDY: Perforin expression in peripher al blood lymphocyte subsets was measured by simultaneous detection of P (intracellular antigen) and cell-surface antigens (CD3, CD4, CD8, CD 16, and CD56) by now cytometry in nonpregnant (NP) and pregnant women in the first trimester (FTP) and at the time of parturition (TP). RESU LTS: The percentage of total P+ cells in peripheral blood compared to nonpregnant women was slightly lower in the FTP but significantly high er at TP. Perforin-positive cells were significantly elevated in T lym phocyte subsets (CD3(+)P(+), CD4(+)P(+), CD8(+)P(+)) in both the FTP a nd TP groups, as was the percentage of CD56(+)P(+) cells. Profound cha nges 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 consi derable part of CD3(+) cells in both the FTP and TP groups are CD3(+)C D56(+)P(+). The average fluorescence intensity (AFI) for P (a measure of P content per cell) was significantly decreased in FTP and increase d in TP groups. CONCLUSIONS: The CD16 molecule is Fc gamma RIIIA which is the only Fc receptor responsible for antibody dependent cell-cytot oxicity (ADCC) of NK and T-cells. In the first-trimester human pregnan cy this mechanism is severely down-regulated compared to both the NP a nd TP groups.