CD4+CD25+ T Cell-Dependent Inhibition of Autoimmunity in Transgenic Mice Overexpressing Human Bcl-2 in T Lymphocytes

Abstract

Regulation of lymphocyte survival is essential for the maintenance of lymphoid homeostasis preventing the development of autoimmune diseases. Recently, we described a systemic lupus erythematosus associated with an IgA nephropathy in autoimmune-prone (NZW × C57BL/6)F1 overexpressing human Bcl-2 (hBcl-2) in B cells (transgenic (Tg) 1). In the present study, we analyze in detail a second line of hBcl-2 Tg mice overexpressing the transgene in all B cells and in a fraction of CD4+ and CD8+ T cells (Tg2). We demonstrate here that the overexpression of hBcl-2 in T cells observed in Tg2 mice is associated with a resistance to the development of lupus disease and collagen type II-induced arthritis in both (NZW × C57BL/6)F1 and (DBA/1 × C57BL/6)F1 Tg2 mice, respectively. The disease-protective effect observed in autoimmune-prone Tg2 mice is accompanied by an increase of peripheral CD4+CD25+ hBcl-2+ regulatory T cells (Tregs), expressing glucocorticoid-induced TNFR, CTLA-4, and FoxP3. Furthermore, the in vivo depletion of CD4+CD25+ Tregs in (DBA/1 × C57BL/6)F1 Tg2 mice promotes the development of a severe collagen type II-induced arthritis. Taken together, our results indicate that the overexpression of hBcl-2 in CD4+ T cells alters the homeostatic mechanisms controlling the number of CD4+CD25+ Tregs resulting in the inhibition of autoimmune diseases.