Seeing that the arthritic joint in both of these cytokine-driven arthritis models is injected with mBSA and that the IL-23 requirement appears to be at the initiation stage, we considered that this timing could be linked to IL-23-dependent cell population changes occurring in the mBSA “primed” joint prior to systemic cytokine administration, i.e. the IL-23 might not in fact be downstream of exogenous cytokine action per se. Here, IL23A is linked to arthritic joint disease.