Characterization of Antibodies in Normal Human Urine.

Certain of the physiochemical and immunochemical properties of the y-globulins of normal human urine have been reported by Webb, Rose, and Sehon (2) and by Franklin (3). These urinary proteins were found to be electrophoretically and antigenically closely related to serum y-globulins, but smaller in size; their molecular weights ranged from 10,600 (2) to 38,000 (3). Sedimentation coefficients S,,20 for the major constituents of the urinary y-globulins were reported to be 1.14 S (2) and 1.6 S (3). Although Webb and associates (2) and, more recently, Rowe and Soothill (4) did not demonstrate 7 S material in total urine concentrates, Franklin (3) noted a small amount of a rapidly sedimenting component with Sw,20 of about 7, in addition to the major 1.5 to 1.6 S peak in y-globulins from a number of different urines. Recently, precipitating and viral neutralizing antibodies were shown to be present in the y-globulins of normal human urine (5, 6). The antibody activity was considered to be probably residing in the 7 S fraction. Porter (7), has shown however, that nonprecipitating fragments with an approximate molecular weight of 55,000, obtained by enzymatic degradation in vitro of rabbit serum antibodies, retain the ability to combine specifically with homologous antigen. The present studies were therefore undertaken to determine whether the low-molecular-weight y-globulins of normal urine possess antibody activity, and preliminary observations (8) suggested that they do.