The Sda antigen in the human kidney and colon.

The range of concentration of the Sda blood group antigen has been determined in the human adult kidney and colon. No Sda antigen was found in 2% of kidneys. Immunofluorescent studies of the kidney showed that Sda is present in the distal convoluted tubules and collecting ducts and occurs in the same location as Tamm-Horsfall protein. No Sda antigen was detected in about 2% of colons. In an additional 6%, no antigen was detected in saline extracts but was present in an insoluble form. In the colon, Sda is sited on the brush borders of the epithelial cells and in the goblet cells. No Tamm-Horsfall protein was identified in the colon.