Binding of alpha-2-macroglobulin trypsin complex to human monocytes in culture.
125I-labelled alpha 2-macroglobulin-trypsin (alpha 2MT) complex bound specifically to freshly isolated human blood monocytes at 4 degrees C but not to B or T lymphocytes, polymorphonuclear leucocytes, erythrocytes or thrombocytes. Binding of 12 pmol/l labelled alpha 2MT to freshly isolated monocytes was low. However, when monocytes were cultured in vitro, binding increased, reaching 10- to 20-fold higher specific binding by 2-4 weeks. Non-specific binding was absent. Considerable variations were observed in binding to monocytes from different cultures (individuals). The half-time of 125I-labelled alpha 2MT complex association to 14-days-old monocyte cultures was about 6 h at 4 degrees C. Dissociation of labelled complex after the addition of a saturing concentration of unlabelled complex was biphasic. About half of the labelled complex dissociated with a half-time of about 1 h, whereas the other half dissociated extremely slowly. At near steady state, half of the receptors were occupied at a complex concentration of about 200 pmol/l and Scatchard analysis showed that the data were adequately described by assuming one class of receptors. It is concluded that human monocytes express a marked increase in binding of alpha 2M complex when developing to macrophage-like cells in tissue cultures.
D002478:Cells, Cultured; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008264:Macrophages / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000378:metabolism*
D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; C028939:alpha-2-macroglobulin-trypsin complex; D000511:alpha-Macroglobulins; D014357:Trypsin