Isolation and characterization of 7S IgG, a γ-fragment, β2-microglobulin and a Bence Jones protein in urine of a patient with plasma cell leukemia

Abstract Large quantities of a monoclonal 7S IgGκ, a κ type Bence Jones protein, and β 2 -microglobulin along with a smaller amoung of a γ-fragemnt were found in the urine of a patient, TSCH, with plasma cell leukemia. The serum of this patinet also contained a monoclonal 7S IgGκ. Comparison of the isolated urinary IgG and the serum IgG disclosed no significant differences between the two proteins with respect to amino acid composition, amino-terminal amino acid sequence, amino sugar composition, sodium dodecyl sulfate acrylamide gel elecgtrophoresis, ultracentrifugation and antigenicity. Both IgG proteins were intact 7S molecules with a γ chain of γl subclass and with a κ chain of VκIII subgroup. A double immunodiffusion study showed that teh γ-fragment represents a portion of the Fc fragment. This γ-fragment was previously shown to be noncovalently bound to β 2 -microglobulin (Seon & Pressman, 1977). A relatively simple procedure was successfully used to isolate a large amoung of β 2 -microglobulin from the urine of the patient.