It is unlikely that the ‘reduced frequencies’ of this MAIT cell population is merely a result of dilution due to expansion of HIV-specific subsets following infection as virus-specific CD8+ T cells do not contribute significantly to the CD161++ CD8+ T cell pool (data not shown and [9]) and MAIT cells are activated by a range of bacteria and fungi (but not viruses) in a MR1-dependent manner. This evidence concerns the gene KLRB1 and infection.