IL33 and rheumatoid arthritis: Even though we observed nuclear IL‐33 expression only in ECs and not extracellularly, we evaluated soluble ST2 levels in serum and observed significantly higher levels in RA patients compared with non‐RA patients (mean ± SEM 158.5 ± 52 pg/ml versus 12.79 ± 13 pg/ml; P = 0.002) (Figure 2D).