The concentrations of IL-1 differed significantly between the RA and OA groups (9.26 (11.1) pg/ml vs. 7.76 (2.6) pg/ml; P < 0.05), and between the OA and asymptomatic organ donor groups (7.76 (2.6) pg/ml vs. 9.08 (1.6) pg/ml; P < 0.05) (values reported are medians (interquartile ranges)). The gene discussed is IL1B; the disease is rheumatoid arthritis.