CHARACTERIZATION OF THE ANTIGENS RECOGNIZED BY 2 MONOCLONAL-ANTIBODIES REACTIVE WITH BASAL-LAYER KERATINOCYTES OF HUMAN EPIDERMIS

Two monoclonal antibodies, GR3 and GR4, reactive with the basal-layer keratinocytes of human epidermis, were derived by immunization of Balb /c mice with glycoproteins isolated from cultured keratinocytes by lec tin-affinity chromatography. Immunoprecipitation of Triton X-100 extra cts from human keratinocytes metabolically labelled with D-[1-C-14]glu cosamine revealed that GR3 recognized a major glycoprotein with migrat ion properties identical with those of a glycoprotein (reduced form M( r) 126000) which was previously shown to be implicated in intercellula r adhesion [Roberts and Brunt (1985) Biochem J. 232, 67-70]. In their unreduced forms the antigens recognized by GR3 and GR4 both migrated a s two bands with M(r) values of 118000 and 147000. Comparison of I-125 -labelled glycoproteins immunoprecipitated by GR3, GR4 and integrin an tibodies revealed that, under reducing conditions, the major band immu noprecipitated by both GR3 and GR4 co-migrated with the alpha(3) and b eta(1) integrin chains. In addition the immunoprecipitate obtained wit h GR4 contained an additional band co-migrating with the alpha(2) inte grin chain. Sequential immunoprecipitation studies with GR3, GR4 and i ntegrin antibodies confirmed that GR3 is directed against the alpha(3) integrin chain, whereas GR4 is directed against the beta(1) chain. Th ese studies also indicate that some of the alpha(3) integrin chains on keratinocytes may be associated with a beta-chain not recognized by t he antisera against the beta(1) integrin chain used in this study.