HUMAN ALPHA-1-MICROGLOBULIN - ITS MEASUREMENT AND CLINICAL-SIGNIFICANCE

α 1‐Microglobulin (α1‐M), also called protein HC, is a low‐molecular‐weight (LMW) glycoprotein (about 30 kDa) with unique physicochemical properties. Using purified urinary α1‐M as a standard and specific antibody against α1‐M, an assay system for α1‐M was developed, and the clinical significance of this protein was investigated by measuring total levels of α1‐M under physiological and pathological conditions. α1‐M is distributed in various body fluids: in serum, it consists mainly of free LMW α1‐M and monomeric IgA–α1‐M complex. The total α1‐M level in serum and urine usually reflects LMW α1‐M variation sensitively, and its determination is quite useful as an indicator of renal glomerulotubular dysfunction and hepatic dysfunction. Serum levels can vary, depending on IgA‐α1‐M complex level, in parallel with the IgA concentration. The heterogeneity of α1‐M purified from different sources of urine by different procedures and underestimation of IgA‐α1‐M complex by solid‐phase antibody assays can be important causes for the discrepancy of serum levels between assays. Copyright © 1990 Wiley Periodicals, Inc., A Wiley Company