These results, in addition to highlighting a significant genetic influence of CD8+ T-cell levels and HLA-DRB1 in LS, also suggest that the increased numbers and activation of CD4+ T-cells found in the BAL of LS patients may be due to interactions between the genes of CD8+ and CD4+ T-cells with HLA-DRB1 and other genetic and/or environmental factors. Here, CD4 is linked to Leigh syndrome.