Further Studies of the Gamma-Related Proteins of Normal Urine

Abstract

The designation "gamma-related" will be applied to any protein antigenically related to-i.e., reacting with antiserum prepared against-human plasma y-globulins.Webb, Rose and Sehon (1) and Franklin (2) have described the urinary proteins of y-electrophoretic mobility. They found that these consisted largely of material of lower molecular weight than, but antigenically related to, the 7S y-globulin of plasma. The protein population described in these two papers overlaps that defined in this and a previous paper (3) by its antigenic characteristics. It has been decided to continue the interim definition based on antigenic properties for several reasons. First, it permits a ready and probably significant delineation of the group of proteins. Next, as will be shown, not all of the y-related proteins are of y-electrophoretic mobility, and much of the urinary protein of -y-electrophoretic mobility is not y-related.The urinary y-protein, defined by either electrophoretic or antigenic criteria, is divisible into two fractions (2, 3): one of higher molecular weight, and apparently identical with plasma 7S .y-globulin; the other of lower molecular weight. Resemblances between the latter and Bence Jones proteins have been described (3).The present paper reports further investigations of the low molecular weight y-related protein of urine. This will be referred to as "y-u protein." It is further compared with Bence Jones proteins, it is tentatively identified in normal serum and cerebrospinal fluid, and it is shown that it is probably not merely a breakdown product of larger plasma y-globulin molecules.

Characterization of Antibodies in Human Urine*

“…This material contained the antigenic groupings I and II described in Bence Jones proteins and other immunoglobulins (31). This observation has also been reported by earlier investigators (6,8). However, our studies showed in addition that material antigenically related to H chains and F fragments of 7 S y-globulin was regularly found in small amounts in the YL-fraction.…”

“…This has been described by other authors (6) and is apparent from the broad distribution of electrophoretic mobility and by the studies presented here in the gel filtration experiments.…”

“…These findings are of interest, as earlier studies have indicated that the yL-globulin may be quantitatively more important than the 7 S y-globulin in urine (2,4,6,16,17). This is also indicated by our results with quantitative precipitation of the gel filtration 7 S and YL-fractions with various antisera.…”

“…In normal as well as in certain pathological proteinurias -y-globulin, 182A-globulin, and the y-related low molecular weight protein (yL-globulin) have been described by several authors (1)(2)(3)(4)(5)(6)(7)38). Antibody activity demonstrable in urine could be expected to be related to any or all of these immunoglobulins.…”

“…Recent studies, however, have given evidence that the urinary L chains, making up most of the YL-fraction, are not the result of a breakdown of serum 7 S y-globulin (6,49). They may be synthesized independently in a way similar to that shown for Bence Jones proteins (50).…”