ample to the purified lipid cell-wall component or the conjugate. [0063] The organic carrier may be a protein including bovine serum albumin (BSA), gelatin, keyhole limpets haemocyanin and the CD1 molecule, or may be a carbohydrate or may be a micelle. [0064] According to another aspect of the invention there is provided a purified lipid cell-wall component or analog or derivative thereof or a con