Objective of this proposal is to develop a novel adhesion-blocking antibody for therapy of chronic inflammatory diseases like asthma and rheumatoid arthritis. Current treatments involve steroids or inhibition of inflammatory cytokines. An alternative approach is modulation of cell adhesion that is expected to limit inflammatory cell recruitment without immunosuppression inherent to anti-TNFalpha or steroid therapy. Leukocyte adhesion is mediated by the selectins. L-selectin binds to endothelial ligands defined by the monoclonal IgM MECA-79. MECA-79 reactive vessels are found in peri-bronchial biopsies from asthmatics and in rheumatoid synovium. The MECA-79 epitope includes a functionally critical 6-O-sulfation of N-acetylglucosamine contained within sialyl-Lewisx type capping groups of O-glycans on endothelial mucins. We have shown that MECA-79 treatment is therapeutic in asthmatic sheep. The MECA-79 epitope is therefore an attractive target for antibody-based anti-adhesive therapy. In specific aim 1 humanized single-chain antibodies specific to the MECA-79 epitope will be generated from phage display libraries. Aim 2 is to obtain a subset that blocks L-selectin binding. Aim 3 is to obtain a further set of antibodies that block lymphocyte adhesion and migration in-vitro and in-vivo. In phase II, resulting antibodies will be tested in disease-relevant animal models. Provided efficacy, a clinical lead will be developed.