Differential expression of KIR/NKAT2 and CD94 molecules on decidual and peripheral blood CD56bright and CD56dim natural killer cell subsets

Objective: To investigate killer inhibitory receptor (KIR) expression by natural killer (NK) cells in early pregnancy. Design: Case-control study of immunologic markers. Setting: University hospital. Patient(s): Thirty pregnant women and 22 nonpregnant women. Intervention(s): Peripheral venous blood sampling and decidual tissue collection after elective abortion. Main Outcome Measure(s): Flow cytometry was used to assess expression of KIR by NK cells in the cell samples. Result(s): In contrast to CD56(bright) peripheral blood NK cells, CD56(dim) cells express killer cell Ig-like receptor KIR/NKAT2. However, KIR/NKAT2 and lectin-like CD94 are present on both subsets of decidual NK cells. We found no differences between peripheral blood NK cell subsets from pregnant and nonpregnant women. Conclusion(s): Our findings demonstrate that NK cell subsets, distributed in accordance with CD56 molecule density on cell surface, express killer inhibitory receptors CD94 and KIR/NKAT2 in a different way. Our data support the view that CD56(bright)KIR/NKAT2(+)CD94(+) decidual NK cells are specialized NK cells that have an important role to play in early pregnancy. ((C) 2004 by American Society for Reproductive Medicine).