Follicular Helper T Cells And Their Subtypes Are Studied In IgG4-related Diseases

Aim:To study the expression and function of T follicular helper(Tfh)cells and its subsets in IgG4-related disease(IgG4-RD).Methods:We collected the peripheral blood and freshly involved tissue cell suspensions from IgG4-RD patients,blood from sex-and age-matched healthy controls were also collected at the same time.Flow cytometry was performed to analyze the expression of Tfh cells and its subsets from peripheral blood and involved tissues of IgG4-RD patients.With RT-PCR technique,we compared the levels of mRNA Bcl-6 and mRNA Blimp-1 from IgG4-RD patients,which were essential transcriptional regulators for the production of Tfh cells.At the meantime,we also compared the serum level and mRNA expression of IL-21 in IgG4-RD,which was important for Tfh cells performing function.The immunohistochemeistry and immunofluorescence technique were used to assess the location of IL-21 and(CD4+CXCR5+)Tfh cells in the involved tissues of IgG4-RD patients,respectively.Furthermore,by cells co-culture in vitro,we explored the ability of circulating Tfh and its subsets to help B cells proliferation,cell damage,apoptosis,differentiation,and producing antibodies in IgG4-RD.Results:The frequencies of(CD4+CXCR5+)T,(CD4+CXCR5+ICOS+)T,(CD4+CXCR5+PD-1+)T,(CD4+CXCR5+ICOS+PD-1)T cells in IgG4-RD patients were significantly higher in the perphrial blood and involved tissues of IgG4-RD patients compared with healthy controls,and the expression of these cells in those involved tissues was much higher than blood.Among them,the percentages of(CD4+CXCR5+ICOS+PD-1)T cells and PD-1 in(CD4+CXCR5+ICOS+)cTfh cells were positively correlated to the serum levels of IgG,IgG4,IgG4/IgG and the number of organ involved.Especially,the latter showed a significant positive corelation with(CD19+CD24-CD38hi)B cell subset,which has been proved producing higher IgG4 than other B cells.The expression of mRNA Bcl-6 in the peripheral blood CD4+ T cells of IgG4-RD showed no difference from healthy controls,while the expression of mRNA IL-21 in PBMCs of IgG4-RD was higher compared with healthy controls,and positively correlated with serum IgG4,IgG,IgG4/IgG values.In the involved tissues of IgG4-RD,both of the(CD4+CXCR5+)Tfh cells and IL-21 showed high expressed,mainly distributed around glandular cells or ectopic GC,and part of them showed diffuse infiltration.Importantly,compared to healthy controls,cTfh cells in IgG4-RD patients could more efficiently facilitate B cells proliferation and cell damage but inhibit cell apoptosis during co-culture in vitro.What's more,cTfh cells in IgG4-RD enhanced naive B cells(CD19+CD27-IgD)differentiate into switched(S)memory B cells(CD19+CD27+ IgD-)and(CD19+CD24-CD38hi)B cells more efficiently than in healthy controls,which resulted in much more IgG4 secretion.Furthermore,by study the function of cTfh subsets in IgG4-RD,we found that it was mainly cTfhl and cTfh2 but not cTfh17 were significantly higher in IgG4-RD patients compared with healthy controls,and they could enhance the ability of B cells differentiation into(CD19+CD24-CD38hi)B cells and producing much more IgG4 antibodies in IgG4-RD,in which the function of cTfh2 cells was more prominent.Conclusion:Tfh cells play a vital role in the pathgenesis of IgG4-RD.The expression of PD-1 in(CD4+CXCR5+ICOS+)cTfh cells may play an important role in the process of promoting germinal center(GC)B cells translate into plasma cells,which mainly secreting IgG4 antibodies.IL-21 might also play a vital role in the pathogenesis of IgG4-RD.What's more,the function of cTfh cells was aberrant activation.Compared to healthy control,Tfh cells from IgG4-RD patient could more efficiently facilitate B cells proliferation and cells damage,but inhibit cell apoptosis.Especially,Tfh cells could also promote B cells differentiation into S memory B cells and(CD19+CD24-CD38hi)B cells,which result in strong immune response and more IgG4 sectreting after being activated by antigens stimulation.And it was cTfh2 cell subsets mainly performing the function.