Furthermore, a comparison of mice bearing either the H2-Ab allele or H2-Aj allelic variant clearly showed profound shaping of the TCR repertoire, along with less efficient thymic selection of CD4+ T cells in the H2-Aj allelic context, and the authors of those studies proposed that the H2-Aj allele confers reduced capacity to present Mtb antigens to the CD4+ T cells that contribute to TB susceptibility (20). Here, CD4 is linked to tuberculosis.