A human leukocyte differentiation antigen family with distinct alpha-subunits and a common beta-subunit: the lymphocyte function-associated antigen (LFA-1), the C3bi complement receptor (OKM1/Mac-1), and the p150,95 molecule.
The human lymphocyte function-associated antigen-1 (LFA-1), the complement receptor-associated OKM1 molecule, and a previously undescribed molecule termed p150,95, have been found to be structurally and antigenically related. Each antigen contains an alpha- and beta-subunit noncovalently associated in an alpha 1 beta 1-structure as shown by cross-linking experiments. LFA-1, OKM1, and p150,95 alpha-subunit designations and their molecular weights are alpha L = 177,000 Mr, alpha M = 165,000 Mr, and alpha X = 150,000 Mr, respectively. The beta-subunits are all = 95,000 Mr. Some MAb precipitated only LFA-1, others only OKM1, and another precipitates all three antigens. The specificity of these MAb for particular subunits was examined after subunit dissociation by high pH. MAb specific for LFA-1 or OKM1 bind to the alpha L- or alpha M-subunits, respectively, while the cross-reactive MAb binds to the beta-subunits. Coprecipitation experiments with intact alpha 1 beta 1-complexes showed anti-alpha and anti-beta MAb can precipitate the same molecules. In two-dimensional (2D) isoelectric focusing-SDS-PAGE, the alpha subunits of the three antigens are distinct, while the beta-subunits are identical. Biosynthesis experiments showed alpha L, alpha M, and alpha X are synthesized from distinct precursors, as is beta. The three antigens differ in expression on lymphocytes, granulocytes, and monocytes. During maturation of the monoblast-like U937 line, alpha M and alpha X are upregulated and alpha L is downregulated. Some MAb to the alpha subunit of OKM1 inhibited the complement receptor type three. LFA-1, OKM1, and p150,95 constitute a novel family of functionally important human leukocyte antigens that share a common beta-subunit.
D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000276:immunology*; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes; D005455:Fluorescent Antibody Technique; D006098:Granulocytes / Q000276:immunology; D006801:Humans; D007525:Isoelectric Focusing; D016169:Lymphocyte Function-Associated Antigen-1; D009000:Monocytes / Q000276:immunology; D011951:Receptors, Complement / Q000276:immunology*; D017463:Receptors, Complement 3b; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D000939:Epitopes; D016169:Lymphocyte Function-Associated Antigen-1; D011951:Receptors, Complement; D017463:Receptors, Complement 3b