Tissue Distribution of Human α1-Microglobulin

Human alpha(1)-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-alpha(1)-microglobulin serum was prepared and observed to react monospecifically in gel diffusion to purified alpha(1)-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-alpha(1)-microglobulin serum in immunodiffusion. The lymphocyte culture supernate was found to contain alpha(1)-microglobulin. Both thymus-derived(T)- and bone marrow-derived(B)-lymphocyte culture media clearly displayed a specific precipitin line against anti-alpha(1)-microglobulin serum when tested with the Ouchterlony immunodiffusion method. The tissue distribution of alpha(1)-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 alpha(1)-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 alpha(1)-microglobulin shares some immunological role in vivo with lymphocytes and(or) is one of the membrane proteins of lymphocytes.