title: Cross-reactivity between streptococcal M surface antigen and human skin.
abstract: Psoriasis can be triggered by haemolytic streptococcal infections. As M protein is a major pathogenic surface antigen in these streptococci, the cross-reactivity between streptococcal M protein surface antigens and human epidermis was investigated. The conserved component common to the few M proteins investigated consists of an alpha-helical 'coiled-coil' configuration, similar to sub-units of human keratin. The amino acid sequence of protein M6, one of the M proteins that has been fully sequenced, was compared with that of 4721 ubiquitous peptides, by computer-assisted analysis using a protein-sequence data bank. Of all human proteins in the data bank 50-kDa keratin type 1 showed the closest homology with protein M6. Further evaluation revealed that this homology mainly involved the heptapeptide repeat patterns, which form the alpha-helical 'coiled-coil' structure, in both M6 and 50-kDa keratin. Cryostat sections of normal, involved and uninvolved psoriatic skin were studied for cross-reactivity with rabbit antisera raised against 10 different M proteins. All these antisera reacted with the stratum corneum of normal and psoriatic epidermis to a variable extent. Staining of keratinocyte cytoplasm was also observed, but this tended to be more prominent in lesional than in uninvolved and normal skin. Some of the M antisera also stained dendritic cells in the upper dermis as well as endothelium and smooth muscle. These cross-reactivities might be relevant to the pathogenesis of post-streptococcal psoriasis.
authors.affiliation: Department of Dermatology, St Mary's Hospital, London, U.K.
authors.forename: J
authors.initials: J
authors.lastname: McFadden
authors.forename: H
authors.initials: H
authors.lastname: Valdimarsson
authors.forename: L
authors.initials: L
authors.lastname: Fry
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D002352:Carrier Proteins; D003429:Cross Reactions / Q000502:physiology; D001330:Electronic Data Processing; D004817:Epidermis / Q000276:immunology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007633:Keratins / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D011565:Psoriasis / Q000235:genetics / Q000276:immunology*; D016415:Sequence Alignment / Q000379:methods
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; C014689:streptococcal M protein; D007633:Keratins