Immunosuppressive drugs on inducing Ag-specific CD4+CD25+Foxp3+ Treg cells during immune response in vivo

A variety of immunosuppressive drugs are currently used in patients with allo-grafts or autoimmune diseases. Though the effects of rapamycin (RPM) and other immunosuppressant on the CD4+CD25+Foxp3+ T regulatory cells (Tregs) were studied, their impact on Ag-specific Tregs during immune response was not well defined. In our studies, we adoptively transferred TCR-transgenic CD4+KJ1-26+ T cells, CD4+KJ1-26+CD25− naïve T cells or CD4+KJ1-26+CD25+ Tregs into syngeneic BALB/c mice. 24 h later, we treated the recipients with OVA immunization and immunosuppressant including rapamycin (RPM), fingolimod (FTY720), cyclosporin A (CsA), mycophenolate mofetil (MMF), leflunomide (LEF), cyclophosphamide (Cy) or none, respectively. The levels and function of CD4+KJ1-26+CD25+Foxp3+ Tregs in draining lymph nodes (dLNs) and spleens were determined at different time points. Significantly higher percentage and cell number of Ag-specific CD4+KJ1-26+CD25+Foxp3+ Tregs were observed in OVA immunized mice treated with RPM or FTY720 compared with mice that received OVA immunization alone. Furthermore, RPM augmented the population of functional iTregs in dLNs and spleens whereas inhibited nTregs during immune response. In contrast to RPM and FTY720, MMF, LEF, CsA, and Cy markedly decreased the levels of Ag-specific CD4+KJ1-26+CD25+Foxp3+ Tregs during immune response. Thus, different immunosuppressive drugs have distinct effects on the Ag-specific CD4+CD25+Foxp3+ Tregs during immune response. The stronger inhibiting effects of MMF, LEF, CsA and Cy on CD4+CD25+Foxp3+ Tregs than on T effectors may block the host immune tolerance potentiality.

► RPM or FTY20 increase Ag-specific CD4+CD25+iTregs in mice immunized with OVA.
► RPM augmented iTregs whereas inhibited nTregs during immune response.
► MMF, LEF, CsA and Cy decrease CD4+CD25+Foxp3+Tregs during immune response.