CD1-restricted T cells: T cells with a unique immunological niche

Until recently, antigen presentation to T cells was defined only by protein s encoded within the MHC locus. That definition has now been expanded to in clude proteins encoded outside the MHC locus, most notably the CD1 family o f proteins. The pathway of CD1-presented antigens diverges from that of MHC processing, indicating that the CD1 antigen-processing pathway may be comp lementary to the MHC pathways. The most surprising finding of the CD1 antig en-presenting system is that the antigens presented by CD1 are not peptides , but rather lipid and glycolipid in nature. The most compelling evidence f or the role of CD1-restricted T cells in immune homeostasis stems from stud ies of mycobacterial infection and autoimmunity. These studies suggest that CD1-restricted T cells promote cell-mediated immune responses to intracell ular infection and protect against anti-self responses. (C) 2000 Academic P ress.