IL4 and synovial sarcoma: It has been shown that autoimmune B cell activation plays a role in the initiation and propagation of SS by producing abnormal antibodies including interferon (IFN)-γ, IL-4, a B cell activating factor and perpetuating chronic inflammation, and also contributes to the development of B cell lymphoma.[2,13] Our experiments indicated that IFN-γ was expressed on endothelia of capillaries in lacrimal glands with SS, whereas the molecule was expressed on interstitial fibroblastic cells in those with GVHD.