Tumor necrosis factor ␣ (TNF␣) is a potent immunomodulator and proinf lammatory cytokine that has been implicated in the pathogenesis of autoimmune and infectious diseases. For example, plasma levels of TNF␣ are positively correlated with severity and mortality in malaria and leishmaniasis. We have previously described a polymorphism at ؊308 in the TNF␣ promoter and shown that the rare allele, TNF2, lies on the extended haplotype HLA-A1-B8-DR3-DQ2, which is associated with autoimmunity and high TNF␣ production. Homozygosity for TNF2 carries a sevenfold increased risk of death from cerebral malaria. Here we demonstrate, with reporter genes under the control of the two allelic TNF promoters, that TNF2 is a much stronger transcriptional activator than the common allele (TNF1) in a human B cell line. Footprint analysis using DNase I and B cell nuclear extract showed the generation of a hypersensitive site at ؊308 and an adjacent area of protection. There was no difference in affinity of the DNA-binding protein(s) between the two alleles. These results show that this polymorphism has direct effects on TNF␣ gene regulation and may be responsible for the association of TNF2 with high TNF␣ phenotype and more severe disease in infections such as malaria and leishmaniasis.

Over half of the inherited predisposition to insulin-dependent diabetes mellitus maps to the region of chromosome 6 that contains the highly polymorphic HLA class II genes which determine immune responsiveness. Analysis of DNA sequences from diabetics indicates that alleles of HLA-DQ beta determine both disease susceptibility and resistance, and that the structure of the DQ molecule, in particular residue 57 of the beta-chain, specifies the autoimmune response against the insulin-producing islet cells.

The low number of CD4+ CD25+ regulatory T cells (Tregs), their anergic phenotype, and diverse antigen specificity present major challenges to harnessing this potent tolerogenic population to treat autoimmunity and transplant rejection. In this study, we describe a robust method to expand antigen-specific Tregs from autoimmune-prone nonobese diabetic mice. Purified CD4+ CD25+ Tregs were expanded up to 200-fold in less than 2 wk in vitro using a combination of anti-CD3, anti-CD28, and interleukin 2. The expanded Tregs express a classical cell surface phenotype and function both in vitro and in vivo to suppress effector T cell functions. Most significantly, small numbers of antigen-specific Tregs can reverse diabetes after disease onset, suggesting a novel approach to cellular immunotherapy for autoimmunity.