Microchimerism and systemic sclerosis.

Systemic sclerosis (SSc) is a connective tissue disease characterized by progressive fibrosis of the skin and internal organs. SSc is an immunologically mediated disease. A prominent immunological abnormality in SSc patients is the presence of circulating autoantibodies against a variety of nuclear proteins. Furthermore, SSc is characterized by the presence of increased numbers of activated T cells, with the prevalence of CD4+ cells, present in the periphery of skin lesions as well as in other organs in the early stages of the disease. We have recently shown the existence of a predominant activation of IL-4-producing Th2-like T cells in patients with SSc, which may account for the major alterations which occur in this disease. SSc has clinical and serological similarities to chronic graft versus host disease (cGVHD), although there are some important differences. T cells, which orchestrate the tissue damage, are present in great amounts in the inflammatory infiltrates in SSc- and cGVHD-affected tissues. More importantly, T cells from cGVHD tissues produce Th2-like cytokines, thus showing a pathogenetic similarity with SSc. SSc has been postulated as a type of cGVHD resulting from the transplacental transfer of cells between mother and fetus. Very recently, we have shown that in SSc, the microchimeric T cells react with the maternal MHC antigens and are able to produce Th2-type cytokines. Both features are characteristics of cGVHD, supporting the hypothesis that SSc is a disease similar to cGVHD.