Expression of Blimp1 mRNA in the PBMCs of patients with RA and the corresponding regulation of IL-21

Abstract

Objective To Investigate the expression of IL-21 and Blimp1 mRNA in Rheumatoid arthritis (RA) patients and the influence on the expression of Blimp1 in peripheral blood mononuclear cells (PBMCs) of RA patients after IL-21 stimulated; To further explore the mechanism of IL-21 and blimp1 in the pathogenesis of RA. Methods Case control study. The samples of peripheral venous blood from 50 RA patients of department of rheumatology of The First Affiliated Hospital of Zhengzhou University and 50 healthy people were collected respectively, then the plasma and PBMCs was separated. IL-21 in plasma was measured by ELISA; the correlation between patients clinical index DAS28, anti-CCP antibody and IL-21 was analyzed. Blimp1 mRNA of patients' PBMCs was detected by qPCR; PMBCs were isolated from RA patient and then cultured in vitro. Blimp1 mRNA level was measured by qPCR and the ratio of CD20 positive B cell and the ratio of CD138 positive cells in all groups were detected by flow cytometry after 72 h stimulated by IL-21 and CD40L. Results IL-21 content in RA patient blood plasma (130.51±11.35)ng/L was significantly higher than that in healthy control(25.46±6.05)ng/L, t=5.39, P<0.05. Besides, IL-21 level also had a close relativity with patients DAS28(r=0.658) and anti-CCP antibody (r=0.674, P=0.039 and 0.035). In addition, the expression level of Blimp1 mRNA in RA patient PMBCs(1.321±0.11)was higher than that in healthy control group(1.000±0.000), Z=-2.48, P<0.05. While after IL-21 and/or CD40L stimulation, Blimp1 mRNA of IL-21 group and CD40L+ IL-21 group(1.084±0.029, 1.157±0.028)were higher than those of control(1.000±0.000)(P=0.002, P=0.001), moreover the expressive level of Blimp1mRNA of CD40L+ IL-21 group was higher than that of control group (t=4.862, P=0.02). Compared to negative control group, the ratio of CD20 positive B cells [2.42±0.35, 2.63±0.33, 6.35(4.85, 6.57), F=278.363, P<0.001] and the ratio of CD138 positive cells(0.474±0.110, 0.668±0.120, 0.955±0.170, F=49.01, P<0.001)in CD40L group, IL-21 group and CD40L+ IL-21 group were much higher and the differences among CD40L+ IL-21 group with CD40L group and IL-21 group were statistically significant. Conclusion IL-21 could promote the level of Blimp1 mRNA in peripheral blood mononuclear cells in RA patient; IL-21 and CD40L could co-promote B cell maturation though regulating Blimp1 mRNA expression and eventually participate in RA pathogenesis.(Chin J Lab Med, 2015, 38: 552-556) Key words: Arthritis, rheumatoid; Interleukins; Repressor proteins; Leukocytes, mononuclear; CD40 ligand