Surface‐bound anti–type II collagen–containing immune complexes induce production of tumor necrosis factor α, interleukin‐1β, and interleukin‐8 from peripheral blood monocytes via fcγ receptor IIA: A potential pathophysiologic mechanism for humoral anti–type II collagen immunity in arthritis

OBJECTIVE: Type II collagen (CII) is a major component of hyaline cartilage, and antibodies against CII are found in a subgroup of patients with rheumatoid arthritis. We undertook this study to investigate whether and how antibodies directed against CII can form solid-phase immune complexes (ICs) with cytokine-inducing properties in a model theoretically resembling the situation in the inflamed joint, in which CII is exposed for interaction with anti-CII antibodies during periods of inflammation. METHODS: Sixty-five arthritis patients with varying levels of anti-native CII antibodies and 10 healthy controls were evaluated concerning anti-CII and cytokines induced in a solid-phase IC model. Monocytes were either depleted or enriched to define responder cells. Antibodies blocking Fc gamma receptors (Fc gammaR) were used to define the responsible T cell surface receptors. RESULTS: ICs containing anti-CII from arthritis patients induced the production of tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), and IL-8. We found a close correlation between enzyme-linked immunosorbent assay optical density values and induction of TNFalpha (r = 0.862, P 99%) after monocyte depletion, and receptor blocking studies showed significant decreases in the production of TNFalpha, IL-1beta, and IL-8 after blocking Fc gammaRIIa, but not after blocking Fc gammaRIII. CONCLUSION: These findings represent a possible mechanism for perpetuation of joint inflammation in the subgroup of arthritis patients with high levels of anti-CII. Blockade of Fc gammaRIIa and suppression of synovial macrophages are conceivable treatment options in such patients.