However, co-expression of CD38 and HLA-DR on the CD161+ MAIT cell subset itself was inversely correlated to the CD161+ MAIT cell frequency (Fig. 3C), indicating that at least an indirect effect of activation (for example at early stages of infection) is likely to be associated with the reduction of the CD161+ MAIT cell subset. The gene discussed is KLRB1; the disease is infection.