Anti-thymocyte globulin (ATG) is used in the treatment of acute organ rejection. We studied in vitro the effect of low-dose ATG on B-cell activation and differentiation to antibody-secreting cells, as this may have an effect on B cell-driven autoimmune diseases, such as pemphigus vulgaris. Immunoglobulin production was analysed in the supernatants of peripheral blood mononuclear cells (PBMC) and CD19+ B cells from healthy donors and from patients with different autoimmune diseases. B-cell proliferation, viability and differentiation were analysed using flow cytometry. Differentiation of B cells to immunoglobulin G (IgG) secreting cells was significantly reduced by ATG, but not by control unspecific IgG from non-immunized rabbits (rIgG). B-cell viability was not altered by sub-depleting concentrations of ATG. In contrast, B-cell proliferation was enhanced by ATG. When PBMC from patients with autoimmune diseases were studied, specific autoantibodies could be detected in 1 out of 10 patients. In this patient, who had pemphigus vulgaris, ATG not only decreased total IgG, but decreased also specific anti-desmoglein-3. In conclusion, these data suggest that ATG at low concentrations inhibits B-cell differentiation and function.
