CD1 has been distinguished from conventional antigen-presenting molecu
les by its ability to present mycobacterial lipoglycans. Here, Rick Fa
irhurst and colleagues postulate that the hydrophobic groove of CD1 bi
nds palmitic acid, displaying diverse, covalently-attached carbohydrat
es to T cells. Such T cells may constitute a previously unappreciated
subset that helps B cells mount an antibody response to polysaccharide
antigens.