Figure 1.

Surface human leucocyte antigen class I (HLA-I) molecules on primary cells from normal human pregnancies. Compared to isotype controls (a), extravillous trophoblast cells are identified by staining with the HLA-G specific monoclonal antibody (mAb) G233 (b). Double labelling with the mAb Tü149 (c) or B1.23.2 (d) confirms that these HLA-G⁺ cells also express HLA-C in the β₂microglobulin-associated conformation. mAb HC10 (e) or L31 (f) that bind open conformers of HLA-C molecules do not bind trophoblast. The mAb recognizing all conformations of HLA-C molecules detect their antigens at the surface of 721.221 cells transfected with HLA-Cw4 (g). The mAb HC10 and L31 also detect their antigens on primary decidual cells identified by gates for CD56⁺, CD3⁺ or cells negative for leucocyte lineage markers (h). In histograms binding of the indicated mAb is shown in grey compared to staining of an isotype control in white.