PHYSICOCHEMICAL AND IMMUNOLOGIC STUDIES OF GAMMA GLOBULINS OF NORMAL HUMAN URINE*

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Abstract
Studies of normal human urine by immunologic and physicochemical techniques have demonstrated that the protein fractions of urine with an electrophoretic mobility similar to that of gamma globulin are antigenically closely related to the serum gamma globulins but differ from them in being only 1/5 to 1/6 their size. The sedimentation coefficient (so20,w) of the urine gamma globulins from 12 subjects varied from 1.1-1.9 Svedberg units (S) with a mean of 1.6 S. The molecular weight of 4 of these ranged from 24,000 - 38,000. Significant heterogeneity of each fraction was apparent. Immunologic studies by quantitative precipitin analyses and agar diffusion methods employing antisera to serum and urine gamma globulins demonstrated significant cross reaction between the 7 S gamma globulin fraction of serum and the urinary gamma globulins. Studies with radioactive I131-labelled 7 S gamma globulin given intravenously to 4 subjects demonstrated that the small fragments present in the urine were derived from the gamma globulin in serum and that they were not synthesized de novo. The possible source and significance of these proteins and their bearing on current theories of glomerular filtration is discussed.