Years ago, we showed that systemic sclerosis (SSc), an immunologically mediated disorder of the connective tissue, is characterized by a predominant activation of IL-4-producing Th2 cells, which may account for the clinical and serological similarities of SSc to chronic graft versus host disease (cGVHD), in which T cells from involved tissues produce Th2-type cytokines. The gene discussed is IL4; the disease is systemic sclerosis.