Purification and structural characterization of LFA-1, a lymphocyte function-associated antigen, and Mac-1, a related macrophage differentiation antigen associated with the type three complement receptor. Academic Article uri icon

abstract

  • LFA-1, an antigen associated with antigen-specific T lymphocyte-mediated killing, and Mac-1, a macrophage differentiation antigen associated with type three complement receptor function, contain alpha chains of Mr = 180,000 and 170,000, respectively, and beta chains of Mr = 95,000. The monoclonal antibodies defining these antigens do not cross-react. The LFA-1 and Mac-1 beta chains are highly homologous or identical, whereas the alpha chains are highly different by tyrosyl tryptic peptide mapping (K├╝rzinger, K., Ho, M. K., and Springer, T. A. (1982) Nature (Lond.) 296, 668-670). T lymphoma cell lines express LFA-1 but not Mac-1 as shown by immunofluorescence and immunoprecipitation. Conversely, some macrophage-like lines express Mac-1 but not LFA-1. Other macrophage-like lines co-express Mac-1 and small amounts of LFA-1. Mac-1 and LFA-1 are present as separate molecules in these cells. [35S]Methionine and [[3H]glucosamine are incorporated into both alpha and beta chains of Mac-1 and LFA-1, showing both chains are endogenously synthesized and are glycoproteins. Cross-linking and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis experiments show that in both Mac-1 and LFA-1 the alpha and beta chains are noncovalently associated in alpha 1 beta 1 quaternary structures. By quantitative immunofluorescence flow cytometry, the EL-4 T lymphoma and P388D1 macrophage-like lines were estimated to express 10(5) LFA-1 and 1.6 x 10(5) Mac-1 molecules/cell, respectively. From these sources the antigens have been purified to homogeneity in 200-400-micrograms quantities by monoclonal antibody affinity chromatography. The purified antigens contain only the alpha and beta subunits.

publication date

  • October 25, 1982