Expression of a NK cell-restricted epitope on decidual large granular lymphocytes

Decidual large granular lymphocytes (DLGL) are the most abundant lymphoid cell type found in the first trimester maternal decidua. The function of DLGL remains controversial, although freshly isolated DLGL have been shown to exert a weak NK activity. We report here the phenotypic characterization of two DLGL subpopulations by immunofluorescence, using mAb against CD56, PEN5 as well as adhesion molecules potentially involved in cell-cell contact between DLGL and trophoblasts. DLGL are CD56bright and express the CD2, CD11a, CD18, CD38 and CD50 molecules, dimly the CD54 molecule, and poorly the CD102 and CD69 molecules. A strong expression of the polysialylated form of N-CAM (or CD56) was also observed on the surface of DLGL. Finally, 40% of CD56bright DLGL cells express the PEN5 epitope, which is selectively expressed on CD56dim cells NK in the peripheral blood. No other phenotypic difference was detected between the CD56brightPEN5+ and the CD56brightPEN5- DLGL populations. Our results show that DLGL are heterogeneous and suggest that the CD56brightPEN5+ DLGL subset belongs to the classical NK cell lineage.