We have previously isolated several IgG rheumatoid factors (RFs) from patients with both rheumatoid arthritis and idiopathic\nthrombocytopenia purpura using phage display system. To study IgG RFs in patients with other autoimmune diseases, phage display\nantibody libraries froma hepatitisCvirus infected patientwith SjÃ?¨ogrenââ?¬â?¢s syndromewere constructed. After panning, a specific clone\nRFL11 was isolated for characterization in advance.The binding activity and specificity of RFL11 to IgGFc fragmentwere comparable\nto those of RFs previously isolated. The analysis with existed RF-Fc complex structures indicated the homology model of RFL11 is\nsimilar to IgM RF61 complex with high binding affinity of about 6 Ã?â?? 10-8 M. This effect resulted from longer complementaritydetermining\nregion (CDR) combining key somatic mutations. In the RFL11-Fc interfaces, the CDR-H3 loop forms a finger-like\nstructure extending into the bottom of Fc pocket and resulting in strong ion and cation-pi interactions. Moreover, a process of\nantigen-driven maturation was proven by somatically mutated VH residues on H2 and H3 CDR loops in the interfaces. Taken\ntogether, these results suggested that high affinity IgG RFs can be generated in patients with SjÃ?¨ogrenââ?¬â?¢s syndrome andmay play an\nimportant role in the pathogenesis of this autoimmune disease.
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