ASSOCIATION OF THE PUTATIVE B-LYMPHOCYTE SURFACE-MOLECULE B7.3 WITH APROTEIN-KINASE ACTIVITY

Monoclonal antibody BB1 was previously shown to recognize the CD80 pro tein as well as a putative B7.3 molecule, both ligands of the importan t T-cell receptors CD28 and CTLA-4. We report that BB1 coprecipitated from detergent lysates of human B- and pre-B-cell lines a protein kina se activity, as detected by solid phase immunoprecipitation followed b y in vitro kinase assay. As other monoclonal antibodies to CD80 did no t co-precipitate any kinase activity, it seems likely that this protei n kinase is associated with the so far poorly characterized putative B 7.3 molecule. (C) 1996 Academic Press, Inc.