Circulating ß cell-specific CD8+ T cells restricted by high-risk HLA class I molecules show antigen experience in children with and at risk of type 1 diabetes.

In type 1 diabetes (T1D), autoreactive cytotoxic CD8+ T cells are implicated in the destruction of insulin-producing ß cells. The HLA-B*3906 and HLA-A*2402 class I genes confer increased risk and promote early disease onset, suggesting that CD8+ T cells that recognize peptides presented by these class I molecules on pancreatic ß cells play a pivotal role in the autoimmune response. We examined the frequency and phenotype of circulating preproinsulin (PPI)-specific and insulin B (InsB)-specific CD8+ T cells in HLA-B*3906+ children newly diagnosed with T1D and in high-risk HLA-A*2402+ children before the appearance of disease-specific autoantibodies and before diagnosis of T1D. Antigen-specific CD8+ T cells were detected using human leucocyte antigen (HLA) class I tetramers and flow cytometry was used to assess memory status. In HLA-B*3906+ children with T1D, we observed an increase in PPI5-12 -specific transitional memory CD8+ T cells compared to non-diabetic, age- and HLA-matched subjects. Furthermore, PPI5-12 -specific CD8+ T cells in HLA-B*3906+ children with T1D showed a significantly more antigen-experienced phenotype compared to polyclonal CD8+ T cells. In longitudinal samples from high-risk HLA-A*2402+ children, the percentage of terminal effector cells within the InsB15-24 -specific CD8+ T cells was increased before diagnosis relative to samples taken before the appearance of autoantibodies. This is the first study, to our knowledge, to report HLA-B*3906-restricted autoreactive CD8+ T cells in T1D. Collectively, our results provide evidence that ß cell-reactive CD8+ T cells restricted by disease-associated HLA class I molecules display an antigen-experienced phenotype and acquire enhanced effector function during the period leading to clinical diagnosis, implicating these cells in driving disease.

Dendritic cells pulsed with antigen-specific apoptotic bodies prevent experimental type 1 diabetes.

Dendritic cells (DCs) are powerful antigen-presenting cells capable of maintaining peripheral tolerance. The possibility to generate tolerogenic DCs opens new therapeutic approaches in the prevention or remission of autoimmunity. There is currently no treatment inducing long-term tolerance and remission in type 1 diabetes (T1D), a disease caused by autoimmunity towards beta cells. An ideal immunotherapy should inhibit the autoimmune attack, avoid systemic side effects and allow islet regeneration. Apoptotic cells--a source of autoantigens--are cleared rapidly by macrophages and DCs through an immunologically silent process that contributes to maintaining tolerance. Our aims were to prevent T1D and to evaluate the re-establishment of peripheral tolerance using autologous DCs pulsed in vitro with apoptotic bodies from beta cells. Immature DCs derived from bone marrow of non-obese diabetic (NOD) mice were obtained and pulsed with antigen-specific apoptotic bodies from the beta cell line NIT-1. Those DCs that phagocytosed apoptotic cells diminished the expression of co-stimulatory molecules CD40 and CD86 and reduced secretion of proinflammatory cytokines. Moreover, these cells were resistant to increase the expression of co-stimulatory molecules after lipopolysaccharide activation. The administration of these cells to NOD transgenic mice expressing interferon-beta in their insulin-producing cells, a model of accelerated autoimmune diabetes, decreased diabetes incidence significantly and correlated positively with insulitis reduction. DCs pulsed with apoptotic cells that express disease-associated antigens constitutes a promising strategy to prevent T1D.