Figure 4

Development and progression of early arthritis in IFN-γ deficient mice. Mono-articular antigen-induced arthritis (AIA) was triggered in mice previously immunized against methylated bovine serum albumin (mBSA); arthritis was induced after an intra-articular (i.a.) injection of mBSA. Plasma and synovial cytokine expression was assessed together with histological measures of arthritis severity during early arthritis (one day after i.a. mBSA injection). (A) Plasma cytokine expression (mean ± SEM; pg/ml) shown in wild-type and IFN-γ-/- mice one day after AIA induction; *P < 0.05. (B) and ( C), representative immunohistochemical staining for IL-1β in joint sections from IFN-γ+/+ and IFN-γ-/- mice respectively; intense positive brown staining (denoted by black block arrows) present in the synovial lining layer, joint exudate and focal areas of inflamed synovium, (original magnification ×10). Arthritis severity was graded in histological sections from IFN-γ+/+ (n = 7) and age matched IFN-γ-/- (n = 6) mice one day post arthritis induction. ( D ). Individual parameters of arthritis severity (mean ± SEM) reported. (E). Representative H&E stained para-sagittal section demonstrating histopathology of a IFN-γ+/+ knee joint processed one day post arthritis induction. ( F). Corresponding section from IFN-γ-/-, showing comparable cellular infiltration, synovial hyperplasia and joint exudate (original magnification ×4). (G) and (H). Representative, Safranin-O/Fast green stained, para-sagittal section demonstrating typical cartilage architecture in arthritic knees on Day 1. Replete GAG staining (red) in articular cartilage; (G) IFN-γ+/+ and (H) IFN-γ-/- (original magnification ×20).