Urinary immunoglobulin G: a routine and highly sensitive technique based on competitive binding.
The evaluation of both small amounts of urinary immunoglobulins and the albumin/immunoglobulin ratio are important indices during the early stages of diabetic nephropathy. For this reason there is at present a need for highly-sensitive and specific routine tests for urinary immunoglobulins. A technique has been designed based on the competition between radiolabelled immunoglobulin G and immunoglobulins in the urine to be tested in binding to an anti-immunoglobulin antibody in solid phase. The immunoglobulin fraction of a rabbit anti-human immunoglobulin antiserum in a basic Ca-carbonate buffer is left to coat highly adsorbent polystyrene microtitre tubes. After the antibody-coated tubes have been saturated with gelatine, a 1/5 dilution of the urine to be tested and an equal volume of purified and radiolabelled human immunoglobulin G are left to incubate and are then added to the antibody-coated tubes. After incubation and repeated washings, radioactivity is counted. This technique has the characteristics of a routine assay for the accurate detection of immunoglobulin G in the urine. It requires only a few microliters of urine, takes only 3 hr to complete (after having coated the tubes) and detects about 120 ng of immunoglobulin G/ml, well below what is needed to assess physiological or pathological values.
D001667:Binding, Competitive; D003920:Diabetes Mellitus / Q000652:urine; D003928:Diabetic Nephropathies / Q000175:diagnosis* / Q000652:urine; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007074:Immunoglobulin G / Q000652:urine*
D007074:Immunoglobulin G