| Background and objectiveRheumatoid arthritis(RA) is a chronic systemic autoimmune disease of unknownaetiology that is characterized by symmetrical synovitis leading to persistent jointdestruction, affecting about0.5%of the adult polulation. Extrafollicular germinalcenters(GCs) can be formed easily in the synovium of RA patients, enabling B cellsplay a role in local inflamation in addition to generating memory B cells and plasmacells, all of which activate immune system and lead to joint destructiion. Although theetiology and pathology remain elusive, the basic view about the pivotal role ofcytokines in promoting synovium cell activaiton and subsequently causing articulardestruction is clear. In the last decades, RA has been considered to be preferentiallymediated by T cells and macrophge, which are important players in thepathophysiology of RA. More recently, increasing evidence of a pivotal role of Bcells involved in immune dysregulation in RA was obtained and fueled by clinical improvements in RA patients receiving B cell depleting therapies such asrituximab,an anti-CD20anti body. As a newly found T lymphocyte subset, Tfh cell(T follicularhelper cell) is found to be involved in the pathogenesis of various autoimmunediseases, one figure mechanism in promoting the autoformation of germinal centerand abnormal positive selection of autoantibody with high affinity. Besides, the Tcell subset can contact with B cells directly by CD40L, which causes the binding ofCD40-CD40L so as to triger the activation of NF-kB and the upregulation of IRF4inB cells, the later downregulates BCL6in turn so as to create condition for the furtherdifferentiation of B cells in germinal center. The key role of Tfh cells in thepathogenesis of autoimmune disease is finished through producing IL-21(Interlukin21) and other cytokines. IL-21is found to control the formation of germinal center byinteracting with B cells directly and promote B cells differentiation into plasma cellsby activating STAT3, but whether other signal pathway involving in plasma celldevelopment exists still need further study. As one of the three key transcriptionalfactors(STAT3， IRF4， Blimp1) in the development of plasma cell, B lymphocyteinduced maturation protein1(Blimp1) is a key transcriptional regulator in plasma cellgeneration and immunogloblin secretion, whose role in auoimmune disease rarelygets explored so far, so dose the corresponding regulaiton of IL-21. The study wasdesigned to explore the expression of IL-21and Blimp1mRNA in Rheumatoidarthritis patients and the effect of IL-21on Blimp1mRNA expression and CD20expression on B cells of cultured PBMCs from Rheumatoid arthritis patients in vitro.To research the possible pathogenetic mechanism of IL-21in Rheumatoid arthritis.Methods1.30Rheumatoid arthritis patients hospitalized in department of Rheumatologyfrom The First Affiliated Hospital of Zhengzhou University dating from2012.10to2013.3and30healthy controls were chosen.2. The level of plasma IL-21in RA patients and controls was measured withELISA； DAS28that reflects disease activity was recorded and the level of auto-antibody against CCP was tested in the department of laboratory, the correlationof both and IL-21level was analyzed.3. Real-time fluorescent quantitative PCR (QRT-PCR)was applied to analyze thelevel of Blimp1mRNA expression in PBMCs of RA patients, and the results werecompared with healthy controls.4. PBMCs were separated and cultured in vitro;Four groups were set accordingto culture condition, namely negatively control,CD40L,IL-21and IL-21plus CD40L.The level of Blimp1mRNA expression in cultured PBMCs was measurd withQRT-PCR72h later after IL-21and/or CD40L stimulation and the rusults werecompared respectively.5. PBMCs were separated and cultured in vitro; The group of negative control,IL-21, CD40L and IL-21plus CD40L were set according to the corresponding culturecondition.The cultured cells were harvested96h later after stimulation and theproportion of CD20positive B cells of each group was analyzed by flow cytometry.Results1. The level of serum IL-21in RA patients(126.31±12.68ng/L) is much higherthan healthy controls (21.26±6.35ng/L)(t=-23.185, P＜0.05)and correlates well withboth DAS28(r=0.102) and anti-CCP (r=0.083)antibody(P＜0.05).2. The expression of Blimp1mRNA in PBMCs from RA patients（1.216±0.21）is higher than healthy controls（1.000±0.00）（Z=-2.41,P＜0.05).3. After stimulation in vitro, the change of Blimp1mRNA expression in eachgroup as follows: There is no significant difference between Group CD40L（1.008±0.027） and negative control（1.000±0.00）,but Group IL-21（1.084±0.029）andGroup IL-21plus CD40L（1.157±0.028）are both higher than negative control(P＜0.05), what’s more, Group IL-21plus CD40is higher than Group IL-21(P＜0.05).4. The propotion of CD20positive B cells (%)in group IL-21（2.63±0.33），CD40L(2.42±0.35)and IL-21plus CD40L （5.60±0.42） were both higher thannegative control（1.62±0.14）(P＜0.05), and the propotion of CD20positive B cells in group IL-21was higher than group CD40L(P＜0.05).ConclusionsThe level of IL-21is upregulated in RA patients and correlates well with DAS28and antibody to CCP, indicating that IL-21may involved in the pathogenesis of RAand correlates with function of plasma cell; The expression of Blimp1mRNA inPBMCs from RA patients is higher than healthy controls and the abnormal expressionfo Blimp1may participate in the pathogenesis of RA; IL-21could involve in thepathogenesis of RA by upregulating the expression of Blimp1so as to promote B celldifferentiation and maturation. |
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