The identification and significance of hypoxanthine in dialyzable transfer factor

The composition of dialyzable transfer factor has been studied. A fraction that had previously been shown to contain the property of transferring delayed hypersensitivity to immunodeficient patients was found to contain hypoxanthine. Removal of hypoxanthine from whole transfer factor by digestion with xanthine oxidase did not impair the ability of the transfer factor to passively sensitize rhesus monkeys. Moreover, studies with pure hypoxanthine indicated that it was not responsible for certain antigen-independent activities in transfer factor such as chemotaxis or cyclic nucleotide accumulation. Digestion of whole transfer factor with xanthine oxidase did not affect its chemotactic activity, but did reduce its effect on cyclic nucleotide accumulation.