Synthesis of C1 inhibitor (C1-INA) by a human monocyte-like cell line, U937.
Human monocytes are known to synthesize many of the components of complement, including C1-INA. In this report we demonstrate that the human monocyte-like cell line U937 is also capable of synthesizing functional C1-INA. This was shown in several ways, including 1) incorporation of tritiated amino acids into antigenic C1-INA, immunoprecipitation, and detection by fluorography; 2) a sensitive ELISA, which allowed quantitation of antigenic C1-INA in cell lysates, and 3) a C2-dependent hemolytic assay in which the functional activity of U937 C1-INA was assayed. Data from the ELISA indicate that U937 cells contain between 2.1 to 12.8 ng of C1-INA per 1 X 10(6) cells. Furthermore, fluorescence-activated cell sorter analysis revealed that approximately 16% of U937 cells carry C1-INA as a surface bound antigen. Other proteins found to be synthesized by U937 cells include C1r, C8, and possibly alpha-2-macroglobulin. These results suggest that the U937 cell line could be a convenient and valuable model for the study of monocyte C1-INA synthesis and physiology.
D000596:Amino Acids / Q000378:metabolism; D000954:Antigens, Surface / Q000032:analysis; D002460:Cell Line; D003174:Complement C1 Inactivator Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000502:physiology; D003175:Complement C2 / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006461:Hemolysis; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis; D009000:Monocytes / Q000032:analysis / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate
D000596:Amino Acids; D000954:Antigens, Surface; D003174:Complement C1 Inactivator Proteins; D003175:Complement C2; D008565:Membrane Proteins; D011506:Proteins; D012967:Sodium Dodecyl Sulfate