TOTAL NONDIALYZABLE SOLIDS (TNDS) IN HUMAN URINE. IX. IMMUNOCHEMICAL STUDIES OF THE R-1 “UROMUCOID” FRACTION*

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Abstract
Uromucoid, the non-ultrafiltrable material of normal urine insoluble in 0.1 [image] veronal buffer of pH 8.6, was demonstrated to be an electrophoretically and ultracentrifugally homogeneous material. Rabbit immune sera to this material gave a single precipitin zone in Ouchterlony gel diffusion plates with the original antigen. Treatment of urinary non-dialyzable solids with cetyltri-methylammonium bromide, dilute ethanol and other methods known to give reproducible fragmentation of uromucoid, resulted in 2 or more zones of precipitation in the gel diffusion against homogenous anti-uromucoid sera. This is interpreted as evidence that uromucoid is fragmented after injection into rabbit foot-pads, with formation of antibodies to some of the fragments as well as to the original molecules. Variations in the rates of gel diffusion of these partial and complete antigens plus multiple antibody formation combine to give several zones of precipitation in the Ouchterlony plates. The presence of 2 zones of precipitation in gel plates when veronal soluble solids of normal urine are diffused against uromucoid immune serum suggests the presence of at least one such "fragment" or short chain length of uromucoid in normal urine. Human tissue from kidney, striated muscle, subcutaneous fat, and skin all contained antigens which gave serological reactions of partial identity with uromucoid immune serum. Human blood plasma, erythrocyte membranes, saliva, bone matrix and seminal fluid contained no substance with demonstrable serologic reactivity to uromucoid immune serum. Complete serologic identity was established between uromucoid and Tamm and Horsfall urinary mucoprotein, but not between uromucoid and any material from sources other than non-dialyzable solids of human urine.