Double transgenic wild type FcRγ bone marrow chimeras showed a robust arthritic phenotype on all limbs, while the double transgenic ITAM tyrosine mutant FcRγ chimeras were totally protected from arthritis development (Figures 5C,D; P = 0.04 for FcRγ KO + 2x WT FcRγ Tg vs. FcRγ KO + 2x YF FcRγ Tg and P = 0.70 for FcRγ KO + 2x YF FcRγ Tg vs. FcRγ KO in connection with the fore limbs; P = 9.2 × 10−3 for FcRγ KO + 2x WT FcRγ Tg vs. FcRγ KO + 2x YF FcRγ Tg and P = 0.96 for FcRγ KO + 2x YF FcRγ Tg vs. FcRγ KO in connection with the hind limbs). This evidence concerns the gene FCER1G and arthritic joint disease.