Transplantation

Donor-type CD4+CD25+ regulatory T cells suppress lethal acute graft-versus-host disease after allogeneic bone-marrow transplantation.Hoffmann, P. et al. J. Exp. Med. 196, 389–399 (2002)

CD4+CD25+ immunoregulatory T cells: new therapeutics for graft-versus-host disease.Cohen, J. L. et al. J. Exp. Med. 196, 401–406 (2002)

CD4+CD25+ regulatory T cells are known to have an important role in inducing tolerance to allogeneic organ transplants. These two studies show that these cells can also suppress graft-versus-host disease (GVHD; the main complication of allogeneic haematopoietic stem-cell transplantation) in mouse models. Cohen et al. show that CD4+CD25+ T cells that are naturally present in the graft regulate GVHD, because their removal from the graft accelerated the development of this disease. The addition of freshly isolated CD4+CD25+ T cells at the time of grafting delayed or even prevented GVHD. Hoffman et al. show that interleukin-10 produced by transplanted CD4+CD25+ T cells is required for full protection and that these cells must be of donor origin.

Dendritic cells

Characterization of a new subpopulation of mouse CD8α+B220+ dendritic cells endowed with type-1 interferon production capacity and tolerogenic potential.Martín, P. et al. Blood 100, 383–390 (2002)

The authors describe a new B220+ subpopulation of immature-like mouse dendritic cells (B220+ DCs) that are present in the thymus, bone marrow, spleen and lymph nodes, and that express low levels of MHC and co-stimulatory molecules. These B220+ DCs share ultrastructural features with human plasmacytoid cells and, in line with this, they produced type I interferon after virus stimulation. In addition, these DCs had reduced T-cell stimulatory potential, which indicates that they might be a physiological subset of tolerogenic DCs.

T-cell development

Thymocyte development in early growth response gene-1-deficient mice.Bettini, M. et al. J. Immunol. 169, 1713–1720 (2002)

In this study, Bettini et al. investigated the role of the transcriptional regulator early growth response gene 1 (Egr1) in thymocyte development. They looked at thymocyte development in Egr1−/− mice on a normal polyclonal T-cell receptor (TCR) background and on different TCR-transgenic backgrounds. The overall thymic cellularity of the Egr1−/− mice was increased, which indicates that Egr1 regulates the size of the thymus. Egr1 is also important for the positive selection of CD4+ and CD8+ single-positive T cells and is a positive regulator of Id3 and Bcl2 expression in response to TCR signalling in double-positive thymocytes.