Immunological mimicry between N-acetyl-beta-D-glucosamine and cytokeratin peptides. Evidence for a microbially driven anti-keratin antibody response.

We discovered recently that a subset of mouse anti-streptococcal mAbs cross-reacted with N-acetyl-beta-D-glucosamine (GlcNAc) and certain cytoskeletal proteins, and recognized both carbohydrate and peptide antigenic determinants. To further study the nature and biologic significance of immunologic mimicry between carbohydrate and peptide Ags, eight human hybridomas secreting anti-GlcNAc mAbs were produced by in vitro stimulation of PBL with streptococcal peptidoglycan-polysaccharide complexes and pokeweed mitogen. All human anti-GlcNAc mAbs described in this study were shown to express marked cross-reactivity with keratin from human skin in the ELISA and Western immunoblot. Mapping of the mAbs with overlapping synthetic decapeptides of the entire amino acid sequence of human cytokeratin 14 revealed that human anti-GlcNAc mAbs recognized specific cytokeratin decapeptides. Four human anti-GlcNAc mAbs recognized a single cytokeratin decapeptide whereas two mAbs reacted with several individual peptide epitopes in different fragments of cytokeratin 14. In addition, two mAbs, 1.C8 and 9.B12, reacted with multiple cytokeratin decapeptides, predominantly in the head domain of the molecule, and their reactivity correlated with positive binding of the mAbs to cytokeratin 14 in the Western immunoblot and with positive staining of human epidermis in the indirect immunofluorescent assay. Finally, we demonstrated that Abs to keratin and synthetic keratin decapeptides were induced in BALB/c mice immunized with GlcNAc-BSA but not with BSA, suggesting that the anti-keratin Ab response in vivo may be driven by nonkeratin Ags containing terminal O-linked GlcNAc.