Functions Of Mica*A5.1 Allele In Ulcerative Colitis In Chinese Patients

AimsThe MHC class I-related molecules A (MICA) is a stress-inducible cell surface antigen that are recognized by immunocytes with NKG2D receptor, including intestinal epithelial Vδ1 γδ T cells, NK cell and CD8+ T cell, which participate in immunological reaction in intestinal mucosa.The present study was aimed to investigate the functions of the MICA*A5.1 allele in the pathogenesis of ulcerative colitis (UC) in Chinese population.Methods The microsatellite polymorphisms of MICA were genotyped in unrelated 124 Chinese patients with UC and 172 ethnically matched healthy controls by a fluorenscently labeled PCR.All the subjects were the Chinese Han nationality in central China.MICA*A5.1 gene were synthesized from total RNA from Hela cell line and amplified by PCR method.The PCR products were cloned into the retroviral vector pCLXSN.MICA*A5 with a full-length cytoplasmic tail was performed by site-directed mutagenesis to delete a guanine before the third GCT repeat in the TM sequence of MICA*A5.1 allele.The mutant MICA*A5 construct was transfected into Raji cells.Soluble MICA in the culture supernatant and IFN-γ were detected by ELISA.The cytotoxicity of NK cell to MICA*A5.1 expressed Raji cell was detected by LDH method.Results The frequency of MICA*A5.1 was significantly higher in UC patients compared with the healthy controls (29.0% vs. 17.4%,P=0.001, Pc=0.005,OR= 1.936, 95%CI: 1.310-2.863).Raji cell with MICA*A5.1 expression produced higher soluble MICA protein than both Raji/A5 cell (1916.35±255.21pg/ml vs. 1304.04±53.94pg/ml, t= 10.839, P<0.01) and Raji/emp cell (1916.35±255.21pg/ml vs. 777.89±32.57pg/ml, t= 5.778, P<0.01), respectively.Raji cells with MICA*A5.1 expression was more resistant to killing of NK cells and less IFN-γ release than Raji cells with full-length MICA expression.Conclusions The MICA*A5.1 allele is significantly associated with Chinese UC patients in central China and functions as influence of soluble MICA and NK cell killing activity in pathogenesis of UC.