Figure 5 IL6, IL8, and PGE₂ secretion in second passage SFB from patients with RA and OA after stimulation with TNFα, the agonistic anti‐TNF‐R1 mAb HTR‐9, or the agonistic anti‐TNF‐R2 mAb UTR‐1 (with or without inhibition of p38). In RA‐ and OA‐SFB (n = 6 each), TNFα significantly induced the secretion of IL6 (A), IL8 (B) and PGE₂ (C) compared with non‐stimulated cells through TNF‐R1. The induction of IL6 (mediated through TNF‐R1) and of PGE₂ (mediated through both TNF‐Rs) was significantly reduced by p38 inhibition in RA‐ and OA‐SFB (A, C). Bars indicate means (SEM). *p<0.05 for the comparison of non‐stimulated and stimulated cells; †p<0.05 for the comparison of cultures with or without SB203580.