Provides, to the authors' knowledge, the first direct evidence for the proposed antigen-presenting function of CD1 molecules and suggests that the CD1 family plays a role in cell-mediated immunity to microbial pathogens. Major histocompatibility complex (MHC) genes; Restriction of the proliferative and cytotoxic responses of human CD4-8- alphabetaTCR+ T cells specific for Mycobacterium tuberculosis by CD1b; Details.