THE MONOCLONAL-ANTIBODY AS02 RECOGNIZES A PROTEIN ON HUMAN FIBROBLASTS BEING HIGHLY HOMOLOGOUS TO THY-1

Recently, we described a novel fibroblast-restricted monoclonal antibo dy (mAb AS02) that recognizes a membrane-bound antigen. Characterizati on and isolation of the corresponding antigen showed that mAb AS02 rec ognized a protein on human fibroblasts that is highly homologous or id entical to human Thy-1 antigen (CD90). Partial amino acid sequencing o f the corresponding mAb AS02 antigen and comparison with known protein s revealed a 100% homology of the sequenced peptides to the human Thy- 1 antigen. Cross-immunodepletion studies with mAb AS02 and an anti-Thy -1 antibody confirmed these results. Utilizing two-dimensional (2D) ge l electrophoresis of fibroblast cell extracts and purified antigen, mA b AS02 and the anti-Thy-1-antibody recognized identical protein spots. Furthermore, we demonstrated many identical biochemical properties of the corresponding AS02 antigen and Thy-1 antigen, such as the molecul ar weight of the core protein and deglycosylation products and the det ection of a GPI anchor. In functional assays, the attachment of fibrob lasts to collagen I and fibronectin was increased after incubation of fibroblasts with mAb AS02. Therefore, the Thy-1 antigen appears to be involved in the regulation of the adherence of human dermal fibroblast s.