Moreover, recent study by Elahi and Horton provided novel insights into the role of T regs in chronic viral infection. This study showed that HIV-specific CD8 T cells restricted by protective HLA-B27/B57 alleles are much more resistant to T reg-mediated suppression than CD8 T cells restricted by non-protective HLA alleles. This resistence to T reg suppression was because CD8 T cells restricted by protective HLA alleles upregulated low levels of T cell immunoglobulin Mucin Protein-3 where they encountered their antigen. Thus, T regs were not able to suppress proliferation of these HIV-specific CD8 cytotoxic T lymphocyte through Tim-3:Galactine-9 interaction. In contrast, HIV-specific CD8 cytotoxic T lymphocyte restricted by non-protective allels upregulated high levels of Tim-3 when they encountered their antigen and were subsequently suppressed by T regs. The lack of suppression of B27/B57-restricted cytotoxic T lymphocyte allows them to continue to proliferate and kill infected targets during chronic infection, which may account for delayed disease progression in persons with protective alleles
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