TLR4 and rheumatoid arthritis: Type II collagen (CII, α1(II)3), the most abundant fibrillar protein of articular cartilage [14], is considered an important autoantigen involved in the pathogenesis of collagen-induced arthritis in mice and RA in humans [15,16] In addition, collagen has been shown to deliver a direct maturation stimulus to DCs [17], possibly via ligation of Toll-like receptor 4 (TLR4) or by binding to cell surface integrins [18,19], suggesting that DCs can present collagen T cell epitopes without additional inflammatory or danger signals.