TLR4 and Arthritis: Consistent with these results, adoptive transfer of macrophage- (MD) or mast cell-depleted (MsD) WT spleen cells into TLR4-/- mice did not restore antibody-induced arthritis or cytokine production in the joints, whereas non-depleted WT spleen cells fully restored arthritis in TLR4-/- mice (Figure 6A, B).