Molecules that interact with the NKT cell antigen receptor and its counterpart antigen presenting molecule, but which inhibit the NKT cell immune function, are administered to a patient. Conditions of particular interest include the treatment of systemic lupus erythematosus (SLE), cancer, atherosclerosis, and allergic disease. In some embodiment of the invention, the inhibitory agent is an anergizing glycolipid, for example .beta.-galactosylceramide. Pharmaceutical formulations of such glycolipids are provided, and find use in the treatment of diseases involving undesirable NKT cell activation.