Chapter 19: Proteins in Plasma and Urine

Proteins in Plasma and Urine provides a comprehensive look at diagnostic techniques like serum protein electrophoresis, which separates albumin from alpha-1, alpha-2, beta, and gamma globulins to reveal characteristic patterns of disease, such as the "bridging" effect in liver cirrhosis or the specific density changes associated with nephrotic syndrome. A significant portion of the text is dedicated to the acute-phase response, explaining how cytokines like interleukin-6 trigger the production of C-reactive protein (CRP) and other positive reactants while decreasing negative reactants like albumin and transferrin. The discussion extends to the complex complement system and its activation pathways—classic, alternative, and lectin—which are vital for innate immunity and the removal of pathogens. Students will also find detailed explanations of hypoalbuminaemia causes, including dilution, redistribution, and increased catabolism, alongside the clinical implications of B-cell malignancies. These disorders, such as multiple myeloma and Waldenström’s macroglobulinaemia, are highlighted through the identification of monoclonal paraproteins and the detection of Bence Jones proteins in urine. Finally, the chapter addresses renal health by distinguishing between glomerular and tubular proteinuria and introducing microalbuminuria as a critical early marker for diabetic nephropathy, while also detailing the pathology of amyloidosis and the extracellular accumulation of insoluble protein fibrils.