COMPLEMENT-DEPENDENT CYTO-TOXICITY IN THE ANALYSIS OF ANTIGENIC DETERMINANTS ON HUMAN HEMATOPOIETIC PROGENITOR CELLS WITH HLA-DR AS A MODEL

  • 1 January 1984
    • journal article
    • research article
    • Vol. 12  (11) , 817-821
Abstract
Complement-dependent cytotoxicity (CDC) assays using anti-Ia antisera have resulted in controversial conclusions about the expression of HLA-DR determinants on human hematopoietic progenitor cells (HPC). The expression of these antigens on CFU-E [erythroid colony forming unit] in particular could often not be demonstrated. The influence of both the antibody and complement concentrations in CDC assays was studied using murine monoclonal and polyclonal anti-Ia (HLA-DR backbone) antibodies and human anti-HLA-DR typing sera. With use of the same anti-Ia antibody concentrations, elimination of CFU-E required significantly more complement than CFU-GM [granulocyte-macrophage colony forming unit] and BFU-E. In CDC assays with antipolymorphic HLA-DR antisera, complete kill of both CFU-E and BFU-E required significantly more complement than of CFU-GM. Insufficient complement concentration could be partly overcome by increasing the antibody concentration. Intrinsic insensitivity of CFU-E to low concentrations of complement could be excluded by experiments using monoclonal anti-HLA-A/B/C backbone antibodies. FACS [fluorescence octinated cell sorter] experiments demonstrated that the density of HLA-DR determinants on CFU-E is lower than on BFU-E and CFU-GM. In CDC assays, antigens with low expression on HPC can easily be overlooked.