CD1-restricted microbial lipid antigen-specific recognition found in the CD8⁺ αβ T cell pool

It is generally accepted that TCR αβ⁺ CD8⁺ T cells recognize immunogenic peptides bound to MHC-encoded class I molecules. This recognition is a major component of the cellular response mediating immune protection and recovery from viral infections and from certain intracellular bacterial infections. Here, we report two human CD8⁺ TCR αβ⁺ T cell lines specific for Mycobacterium tuberculosis Ags presented in the context of CD1a or CD1c Ag-presenting molecules. These T cells recognize lipid Ags and display cytotoxicity as well as strong Th cell type I cytokine responses. By extending presentation by the CD1 system to the major TCR αβ CD8⁺ T cell pool, this system gains wider applicability beyond the double negative subset of T cells previously shown to have this reactivity. This implies that previous assumptions about the role of CD8⁺ T cells in microbial immunity may require revision as the relative proportions of CD1-restricted and MHC class I-restricted CD8⁺ T cells are further defined.