CD1 and MHC II find different means to the same end

CD1 molecules are a third family of antigen-presenting molecules and are the only one specialized to present lipid-containing antigens. Some CD1 molecules traffic to the same intracellular compartments as MHC II molecules. Moreover, MHC II and the class II-associated invariant chain influence CD1d trafficking. Despite this intersection between the MHC II and CD1 pathways, CD1 proteins use a mechanism entirely different from MHC II to traffic to late endosomes to acquire antigens. Recent experimental evidence has illuminated these unique aspects of the CD1 antigen-presentation pathway.