CD4+ and CD8+ T cells mediate adoptive immunity to aerosol infection of Mycobacterium bovis bacillus Calmette-Guérin.

An adoptive-transfer model using recombinase activation gene-deficient (RAG-1-/-) mice was developed to evaluate CD4+ and CD8+ T cell responses to infection with Mycobacterium bovis bacillus Calmette-Guérin (BCG). After receiving immune, unfractionated T cells or T cell subsets isolated by fluorescence-activated cell sorter, the RAG-1-/- mice were exposed to aerosol BCG, and the bacteria load in the infected organs was examined 4 weeks later. Adoptive immunity was expressed more effectively in the spleens than in the lungs. Although CD4+ or unfractionated T cells protected both lungs and spleens, CD8+ T cells conferred significant protection only in the spleens and not in the lungs. The results confirm that in addition to CD4+, CD8+ T cells also play a role in the prevention of bacterial dissemination. This transfer model may be useful for dissecting T cell responses to mycobacterial infection.