Tissue Distribution of Human α1-Microglobulin

Abstract

Human α₁-microglobulin was isolated from the urine of patients with tubular proteinuria, and its molecular weight was established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis at 33,000 daltons. The carbohydrate content was 21.7%. Anti-α₁-microglobulin serum was prepared and observed to react monospecifically in gel diffusion to purified α₁-microglobulin, as well as to normal human serum and urine. Sera from the domestic chicken, mouse, rat, rabbit, dog, calf, cow, goat, sheep, and horse, however, did not react to anti-α₁-microglobulin serum in immunodiffusion. The lymphocyte culture supernate was found to contain α₁-microglobulin. Both thymus-derived(T)- and bone marrow-derived(B)-lymphocyte culture media clearly displayed a specific precipitin line against anti-α₁-microglobulin serum when tested with the Ouchterlony immunodiffusion method. The tissue distribution of α₁-microglobulin was studied under immunofluorescence, and a positive staining was recognized on the lymphocyte surface. Identical staining patterns were noted on both T and B lymphocytes, though B lymphocytes took a more intense stain. It would thus seem quite possible that lymphocytes are the primary source of α₁-microglobulin and that this is filtered through the glomerular basement membrane and partly reabsorbed by the renal tubules. This, then, would suggest the possibility that α₁-microglobulin shares some immunological role in vivo with lymphocytes and(or) is one of the membrane proteins of lymphocytes.