Cd1, Tuberculosis, and the Evolution of Major Histocompatibility Complex Molecules

Although the role of class I and class II MHC in adaptive immunity against microbial pathogens is clear, the participation of nonpolymorphic MHC molecules in host defense remains less well defined. Roles for murine class I MHC molecule Qa-2 and class Ib molecule H2-M3 have been suggested 1,2,3, and accumulating data have prompted speculation that CD1 family members may be important in immunity against pathogenic mycobacteria and parasites 4. In this issue, Spada et al. report the restriction of at least some human Vγ2/Vδ1 T cells, the most common tissue γ/δ T cells, by CD1c 5. Like other populations of CD1-restricted T cells, as discussed further below, the CD1c-restricted cells were autoreactive in vitro. These cells produced IFN-γ, but not IL-4, and displayed cytotoxicity against CD1c⁺ targets, leading the authors to...