A Study About The Influences Of Follicular T Helper Cells And Interleukin-21 In Mice Ulcerative Colitis

Purpose: Our study was aimed at investigating role of follicular T helper cells(Tfh) and Interleukin(IL)-21 in the development of ulcerative colitis(UC), and the relationship between IL-21 and Tfh cells in colitis microenvironment.Methods: Wild-type(WT) and IL-21 knockout(IL-21KO) mice was been used, both on the same genetic background(C57BL/6J). The mice were induced to UC by DSS. WT mice were divided into 5 groups: A1(oral water), A2(oral 3%DSS), A3(oral 3%DSS + intraperitoneal injection anti-IL-21), A4(oral 3%DSS + intraperitoneal injection Ig G), A5(oral 3%DSS + intraperitoneal injection water), IL-21 KO mice were divided into 2 groups: B1(oral water) and B2(oral 3%DSS). 6 mice in each group. Isolated and cultured the Lamina Propria Mononuclear Cell(LPMCs) which were extracted from mice in A2, then divided into 3 group: C1, C2 and C3, added Ig G, anti-IL-21 and IL-21 to the culture medium respectively. Tfh cells proportion and Tfh-associated Molecules(CXCR5, PD-1, CD40 L, ICOS and Bcl-6) expression of mice colon tissues in A1, A2, B1, B2 were detected by flow cytometry and PCR respectively; IL-21 expression of mice colon tissues in A1, A2 was detected by ELISA and PCR; compared the inflammation grading of mice colitis in A2, B2; Tfh cells proportion and inflammation grading of mice colon tissues in A3, A4 and A5 were compared; Tfh cells proportion and Tfh-associated Molecules(CD40L, ICOS and Bcl-6) expression of mice colon tissues in C1, C2, C3 were detected by flow cytometry and PCR respectively.Results: 1. Tfh cell proportion and Tfh-associated Molecules expression of mice colontissues in A2 were higher than in A1, the differences were significantly(P<0.05), but there was no difference between B1 and B2. Moreover, in WT mice, Tfh cells proportion and Tfh-associated Molecules expression were higher than in IL-21 KO mice, no matter induced by DSS or not. 2. IL-21 expression levels of mice colon tissues in A2 were higher than in A1(P<0.001). 3. Inflammation grading of mice colitis in A2 was higher than in A1(P=0.006). 4. Inflammation grading of mice Colitis in A3 was lower than in A4 and A5(P=0.003, P=0.004), but there was no difference between A4 and A5. The results of Tfh cells proportion were similarly. 5. Tfh cells proportion and Tfh-associated Molecules expression of mice colon tissues was lowest in C2 and was highest in C3, the differences were significantly.Conclusion: 1. Tfh cell and IL-21 promote the development of mice UC. 2. Blockade of Endogenous IL-21 ameliorates DSS-induced Colitis. 3. IL-21 promoted the proliferation and secretion of Tfh cell.