IL21 and rheumatoid arthritis: In the stratified analysis by RF status, pooled associations were found between RF− RA risk and IL-21 rs6822844 polymorphism in the homozygote comparison (OR = 0.52, 95% CI = 0.32–0.84, Pheterogeneity=0.466, P=0.008, Figure 6) and the recessive genetic model (OR = 0.49, 95% CI = 0.31–0.80, Pheterogeneity=0.651, P=0.004) (Table 2).