Human postthymic precursor cells in health and disease. VII. Immunoregulatory circuits of the peripheral blood mononuclear cells from patients with progressive systemic sclerosis.

The study of T cell subpopulations and their immunoregulatory circuits in 9 patients with progressive systemic sclerosis (PSS) and 9 age/sex matched controls showed: 1. Normal postthymic precursor autologous rosette-forming T cells (Tar cells). 2. Normal T cells with receptors for the Fc portion of IgG(Ty). 3. Decreased T cells with receptor for Fc portion of IgM(Tmu). 4. Normal function of postthymic precursors. 5. Normal Concanavalin-A-induced and spontaneously-expanded suppressor cell functions. 6. Abnormally increased T helper cell function. These findings suggest that the primary immunoregulatory aberration in PSS is at the level of Tmu cells and their helper function. Relationship between this T cell disturbance and fibroblast function may explain the pathogenesis of PSS.