Synthetic peptide segments from the Escherichia coli porin OmpF constitute leukocyte activators.

After characterization of the porin OmpF and selection of molecular structures responsible for leukocyte activation by using computer-assisted epitope analysis, the analogs OmpF (153-174) (containing amino acids 153 to 174), OmpF (157-174), and OmpF (275-285) were synthesized and tested. Like the native protein, the segments were mitogenic for BALB/c splenocytes and induced B lymphocyte differentiation into antibody-producing plasma cells and tumor cytotoxicity of macrophages against the fibroblast cell line L929. We thus demonstrated that defined peptide segments are responsible for the leukocyte-activating properties of a major bacterial surface protein.