DISTRIBUTION OF IMMUNOREACTIVE TAMM-HORSFALL PROTEIN IN VARIOUS SPECIES IN THE VERTEBRATE CLASSES

A sheep antibody to human Tamm-Horsfall protein, the major protein in normal urine, was used in an immunohistological study of organs of 48 species of vertebrate animals, representing the classes Mammalia, Aves , Reptilia, Amphibia, Osteichthyes and Chondrichthyes. Immunoreactivit y was shown in the thick limb of the loop of Henle in the kidney of ma mmals, but there was no reactivity with tissues of birds or reptiles. Superficial layers of the skin of several amphibians and fish, superfi cial layers of the oral mucosa and gills of fish, and the distal tubul es of the kidney of some amphibians, reacted with the antibody. Immuno reactivity with mammalian kidney was removed by passage of the antibod y down an immunoadsorption column coated with human Tamm-Horsfall prot ein, and amphibian immunoreactivity was removed by incubation of the a ntibody with material prepared from frogs in the same way as Tamm-Hors fall protein. These findings suggest that immunoreactive Tamm-Horsfall protein appeared early in vertebrate phylogeny, initially in skin and gills and later in kidney, and that although conserved in evolution, it shows antigenic differences between amphibians and mammals. Its dis tribution is consistent with the hypothesis that it acts as a waterpro ofing agent.