From old results to new perspectives: a look at interferon's fate in the body.

In a previous report, we presented preliminary data on interferon-alpha A (IFN-alpha A) pharmacokinetics through the simultaneous study of distribution of the radiolabeled protein by numerical dynamic scintigraphy and the trichloroacetic acid (TCA)-precipitable radioactivity in whole blood and serum, as well as the radioactivity linked to blood mononuclear cells. The interferon preparation then used was contaminated with free iodine which gave parasite images and counts. Here we present further analysis of those data, enlightened by additional information collected in new studies with interferon preparations without free iodine. Interferon uptake by the kidneys, liver, and heart was a consistent finding. On the contrary, images in stomach and duodenum seem mostly related to their well-known iodine uptake. At present, whether interferon is present in saliva and nasal secretion is unclear. The extent to which blood radioactivity corresponded to blood cells or plasma was analyzed. TCA-precipitable radioactivity measured after administration of filtered radiolabeled interferon was mainly confined to serum. The marginal amount bound to cells seemed to be in leukocytes. Current research points to compare the pharmacokinetic profiles of IFN-alpha and IFN-gamma.