Abstract: [Abstract]   Objective   To study the role of the keratin peptides homologous with M protein in the pathogenesis of psoriasis. Methods   Keratin peptides homologous to M protein were synthetized chemically. The sequences of amino acid residues for these peptides were ALEEAN, LKKDVDC, GLRRVLDE and RLKYENELA, respectively. The levels of interleukin (IL)-2, IL-4 and interferon (IFN)-γ were detected by double-antibody sandwich ELISA assay. The proliferation of peripheral blood mononuclear cells (PBMCs) was detected by MTT method. The keratinocytes (HaCaT) were co-cultured with synthetic peptides. The proliferation of HaCaT was detected by MTT method. Results   The expression levels of IL-2, IL-4 and IFN-γ were significantly higher in psoriatic PBMCs cultured with synthetic ALEEAN and LKKDVDC than those in normal PBMCs. These three cytokines were not detected in the cell culture supernatants of homologous peptides GLRRVLDE and RLKYENELA. The proliferation of HaCaT was promoted in synthetic peptides ALEEAN, LKKDVDC and GLRRVLDE co-treated with keratinocyte growth factor (KGF) (P < 0.05). Conclusion    The keratin peptides homologous with M protein could promote proliferation of PBMCs and HaCat in patients with plague psoriasis, which may play a certain role in the pathogenesis of psoriatic aggravation and maintenance after hemolytic streptococcus infection.

Key words: Psoriasis, Streptococcus, haemolysis, keratinocytes, bacterial proteins, blood proteins, monocytes, 白细胞介素2