RECOGNITION OF MURINE INTEGRIN BETA(1) BY A RAT ANTI-STROMAL CELL MONOCLONAL-ANTIBODY

Previous studies with the rat monoclonal antibody KMI6 had localized i ts antigen in vivo to a discrete subpopulation of marrow stromal cells . The KMI6 antigen has now been identified as the murine homolog of in tegrin beta(1) by amino acid sequence analysis and by cross-reactivity with antiserum to the avian integrin beta(1). The relative tissue abu ndance of murine integrin beta(1) was determined by Western blot. Alth ough immunoperoxidase staining of fixed murine hematopoietic tissues d emonstrated an abundance of intracellular beta(1), few primary-derived cells of lymphohematopoietic origin were surface positive as assessed by immunofluorescence and flow cytometry. Fetal erythroblasts provide d the only exception. In contrast, the antigen was readily detected on the surface of several cultured cell lines in association with a vari ety of or chains. The biochemical properties of the surface labeled mu rine integrin beta(1) were similar to those of its human counterpart, exhibiting an altered electrophoretic migration under reduced conditio ns or following N-glycanase treatment. The antibody recognition of the protein was insensitive to glycosylation state, presence of divalent cations, detergents, or transfer to a nitrocellulose membrane. However , on Western blot, the epitope was lost on reduction of the protein, s uggesting that it is conformation dependent. These data indicate that although KMI6 epitope is widely distributed, its surface expression in vivo may be restricted within lymphohemopoietic tissues.