Lymphocytes are covered with sugars. Some of the oligosaccharides on lymphocytes may be recognized by specific lectins such as the selectins, but what other functions do all of these oligosaccharides serve? Two recent papers in Cell(Moody et al., 2001) and Immunity(Daniels et al., 2001) describe a novel role for glycosylation in the thymus—regulating the interaction of MHC class I molecules with CD8 during thymocyte maturation.