Although Syk (-/-) mice die shortly after birth, immune cells derived from these mice respond abnormally during antibody-dependent stimulation through FcεR or FcγR while B-cell differentiation and BCR functionality are similarly altered [8–11].Consistent with these deficits at the cellular level, mice with a conditional deletion of Syk are protected in antibody-mediated models of arthritis [12–14]. Here, SYK is linked to Arthritis.