IL1B and arthritic joint disease: Consistent with the results of our in vitro experiments (Figure 3A-D), recombinant IL-12 increased the expression of IFN-γ and IL-1β in the joints of TLR4-/- mice with arthritis, whereas neither recombinant IL-1β nor IFN-γ altered joint IL-12p35 expression levels (Figure 4B).