Several studies have demonstrated that the synovial tissue of animal models of arthritis, such as CIA, adjuvant-induced arthritis (AA), antigen-induced arthritis (AIA), streptococcal cell wall (SCW) arthritis, and SKG (ZAP-70 mutation model, harbor a strain of a recessive mutation of the gene encoding an SH2 domain of ζ-associated protein 70 (ZAP-70), a key signaling molecule in T cells), express and synthesize an array of pro-inflammatory molecules (IL-1ß, IL-6, and TNFα) at the onset that determines the aggressive damaging disease phenotype (19). Here, IL6 is linked to arthritic joint disease.