058 Identification Th2 cell epitopes in NC16A domain on bullous pemphigoid

Abstract

Bullous pemphigoid (BP) is a cutaneous autoimmune inflammatory disease characterized by autoantibodies directed against BP180-NC16A, a transmembrane protein of epidermal basal cells. In this study, we examined and mapped the fine specificity of T cell epitope to NC16A. As IL-4 secretion is a marker of Th2 antigen-specific activation, PBMCs from 43 BP patients were collected and tested for IL-4 cytokine responses to a complete panel of 22 overlapping peptides spanning the BP180-NC16A domain by ELISPOT assay. Results revealed that IL-4 responses were significantly stronger for three peptides, P14, P18 and P21, in 27 BP patients, which representative aa492 to aa513 in NC16A domain. Further, Flow cytometry and ELISA analysis showed that those three peptides were able to stimulated BP patient’s PBMCs proliferation, B cells activation, pathogenic autoantibodies production, and linearly associated with BP180 titer in BP patients. As other studies have reported, HLA class II regions are linked to BP susceptibility in the Caucasian and Japanese population. We analyzed HLA I/II allele types of 43 Chinese BP patients and 500 healthy controls and found that HLA-DQB1*0602/0202, DRB1*1201/0101/0403/1602 were associated with BP in Chinese Hans population. To further define HLA restriction of those three peptides, we employed HLA-DQ, HLA-DP and HLA-DR neutralizing antibody to blocking antigen presenting during ELISPOT assay. The data showed that HLA-DR antibody could completely block P21 induced IL-4 sections while HLA-DQ and HLA-DP antibody has no effect on this process, which indicated that HLA-DR was involved in the P21 induced antigen presentation process. The P14 and P18 peptides HLA restriction will be confirmed by further study. In conclusion, our research identified aa492 to aa513 as a specificity of T cell epitope to NC16A, those regions are HLA-DR restriction and have the ability to stimulated BP patient’s T cells proliferation, B cells activation and pathogenic autoantibodies production. This results may contribute to the understanding the pathogenesis of BP.