Immunity to glycolipid antigens in microbial infections

T cells recognize ligands of different chemical structures. Recently, it ha s become clear that also self glycosphingolipids and bacterial lipoglycans may act as T cell stimulatory ligands. This type of antigen recognition is restricted by the non-polymorphic CD1 molecules, which have a structure res embling that of classical MHC molecules. Glycolipids insert their hydrophob ic lipid tails in two pockets below the antigen-binding groove and position their hydrophilic heads on the external part of CD1 molecules. TCR interac ts with these carbohydrates and discriminates their structural variations. Glycolipid-specific T cells may provide protection during bacterial and par asite infection probably with different mechanisms: by secreting pro-inflam matory lymphokines, by the direct killing of infected target cells, and by helping specific B cells in Ig production. Lipoglycans represent excellent candidates for new anti-microbial vaccines due to their wide distribution i n the microbial world and their structural composition which does not chang e and thus cannot give rise to escape mutants. Moreover, these vaccines mig ht induce anti-microbial protective T cell responses in the whole populatio n due to the non-polymorphic nature of CD1 presenting molecules.