HLA-G5 is secreted by erythroblasts but not by mature erythrocytes. (A) Detection of HLA-G5 in the supernatants of a 2-phase liquid culture from light-density cord blood cells using an HLA-G5-specific ELISA. The culture supernatant of M8-HLA-G5 cells was used as positive control and HLA-G5 concentration was more than 70 ng/mL. No HLA-G5 proteins were detected in the culture supernatant of KG1a leukemic cells used as negative control. (B) Immunolocalization of HLA-G5 in erythroblasts but not in mature erythrocytes from a 16-week fetal liver. Magnification is × 600. (C) Immunohistochemistry analysis of 16-week fetal BM using the 5A6G7 mAb. (D) Immunohistochemistry analysis of HLA-G5 expression by erythroid cells on paraffin-embedded bone marrow section from an 82-year-old adult. Magnification is × 400 in panels C and D.