Regulatory T Cells Fail to Suppress Fast Homeostatic Proliferation In Vitro.

Homeostatic proliferation (HP) is a physiological process that reconstitutes the T cell pool after lymphopenia involving Interleukin-7 and 15 (IL-7 and IL-15), which are the key cytokines regulating the process. However, there is no evidence that these cytokines influence the function of regulatory T cells (Tregs). Since lymphopenia often accompanies autoimmune diseases, we decided to study the functional activity of Tregs stimulated by HP cytokines from patients with rheumatoid arthritis as compared with that of those from healthy donors. Since T cell receptor (TCR) signal strength determines the intensity of HP, we imitated slow HP using IL-7 or IL-15 and fast HP using a combination of IL-7 or IL-15 with anti-CD3 antibodies, cultivating Treg cells with peripheral blood mononuclear cells (PBMCs) at a 1:1 ratio. We used peripheral blood from 14 patients with rheumatoid arthritis and 18 healthy volunteers. We also used anti-CD3 and anti-CD3 + IL-2 stimulation as controls. The suppressive activity of Treg cells was evaluated in each case by the inhibition of the proliferation of CD4+ and CD8+ cells. The phenotype and proliferation of purified CD3+CD4+CD25+CD127lo cells were assessed by flow cytometry. The suppressive activity of the total pool of Tregs did not differ between the rheumatoid arthritis and healthy donors; however, it significantly decreased in conditions close to fast HP when the influence of HP cytokines was accompanied by anti-CD3 stimulation. The Treg proliferation caused by HP cytokines was lower in the rheumatoid arthritis (RA) patients than in the healthy individuals. The revealed decrease in Treg suppressive activity could impact the TCR landscape during lymphopenia and lead to the proliferation of potentially self-reactive T cell clones that are able to receive relatively strong TCR signals. This may be another explanation as to why lymphopenia is associated with the development of autoimmune diseases. The revealed decrease in Treg proliferation under IL-7 and IL-15 exposure can lead to a delay in Treg pool reconstitution in patients with rheumatoid arthritis in the case of lymphopenia.

Dendritic Cells Transfected with MHC Antigenic Determinants of CBA Mice Induce Antigen-Specific Tolerance in C57Bl/6 Mice.

BACKGROUND: Nonspecific immunosuppressive therapy for graft rejection and graft-versus-host disease (GVHD) is often accompanied by severe side effects such as opportunistic infections and cancers. Several approaches have been developed to suppress transplantation reactions using tolerogenic cells, including induction of FoxP3+ Tregs with antigen-loaded dendritic cells (DCs) and induction of CD4+IL-10+ cells with interleukin IL-10-producing DCs. Here, we assessed the effectiveness of both approaches in the suppression of graft rejection and GVHD. METHODS: IL-10-producing DCs were generated by the transfection of DCs with DNA constructs encoding mouse IL-10. Antigen-loaded DCs from C57BL/6 mice were generated by transfection with DNA constructs encoding antigenic determinants from the H2 locus of CBA mice which differ from the homologous antigenic determinants of C57BL/6 mice. RESULTS: We found that both IL-10-producing DCs and antigen-loaded immature DCs could suppress graft rejection and GVHD but through distinct nonspecific and antigen-specific mechanisms, respectively. Discussion. We provide data that the novel approach for DCs antigen loading using DNA constructs encoding distinct homologous determinants derived from major histocompatibility complex genes is effective in antigen-specific suppression of transplantation reactions. Such an approach eliminates the necessity of donor material use and may be useful in immunosuppressive therapy side effects prevention.

Comparison of CD4+CD25hiFoxP3+ Treg Induction by pIL-10-Transfected Dendritic Cells in Different Mouse Strains.

Tolerogenic dendritic cells (tolDCs) and T-regulatory cells (Tregs) are involved in maintaining tolerance to self-antigens and foreign antigens. The cells are used as therapeutic tools for inducing tolerance to transplanted organs or tissues. We investigated the possibility of inducing Tregs in splenocyte cultures using DCs transfected with a DNA construct encoding mouse interleukin-10 (DCpIL-10). DCs were derived from bone marrow cells in the presence of rmGM-CSF and rmIL-4 and electroporated with a plasmid encoding mouse IL-10. Furthermore, DCpIL-10 was cocultured with syngeneic splenocytes. The CD4+CD25hiFoxP3+ Treg frequency, IL-10 expression, and inhibition of the mixed lymphocyte reaction were evaluated. C57Bl/6 and CBA mice differ in their initial frequency of CD4+CD25hiFoxP3+ Tregs and baseline IL-10 production. Also, the effectiveness of CD4+CD25hiFoxP3+ Treg upregulation by tolDCpIL-10 was different. In this study, DCpIL-10 from C57Bl/6 mice induced CD4+CD25hiFoxP3+ Tregs in syngenic splenocytes, which was accompanied by an increase in the IL-10 production and a decrease in the proliferation of splenocytes in response to the alloantigen. DCpIL-10 may be used to induce CD4+CD25hiFoxP3+ Tregs and the regulatory potential of splenocytes.