HLA-D and -DR antigens on human amniotic fluid cells. II. Heterogeneous expression of HLA-DR and other cell surface markers

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Abstract
To evaluate further the feasibility of HLA typing for prenatal diagnosis human amniotic fluid cells (AFC) known to express HLA-A, -B and -C antigens were tested for the presence of HLA-DR antigens using type-specific antisera in the microcytotoxicity assay and a monoclonal antibody directed against the common HLA-DR structure (cDR) in indirect immunofluorescence. Prenatal typing of HLA-DR on AFC in the microcytotoxicity test was possible in only 1 of 8 families studied. The detected DR2 antigen was confirmed by postnatal typings of cord blood lymphocytes. Thereafter, 23 different AFC cultures were tested with monoclonal antibodies in indirect immunofluoresence. Only 6 cultures were partially positive (23-35% fluorescent cells) with the monoclonal cDR antibody while all AFC cultures demonstrated strong positive fluoresence (68-100%) with a monoclonal antibody against the common HLA-A, -B and -C structure (cHLA). Evidently, only a small subpopulation of AFC expresses class II (HLA-DR) antigen in contrast to the nearly ubiquitous expression of class I (HLA-A, -B and -C) antigens. The heterogeneous expression of cell surface antigens within the various AFC cultures was substantiated with monoclonal antibodies directed towards cell surface antigens of the OKT, OKM and Lyt series that were found to be characteristic for subpopulations of lymphoid and hematopoetic cells. Thus, at present, HLA-DR typing is not reliable for prenatal diagnosis.