Figure 1.

BCG uptake by bladder urothelial cells. Representative photomicrographs indicating uptake of acid fast bacteria by the urothelial cells and infiltration of PMNs. Twenty four hours after bladder instillation with BCG, bladders were removed and stained with fast acid (A-C) or H&E (D-F). Acid fast-positive bacteria were detected within umbrella cells and underlying urothelial cells, indicating that BCG is taken up by an apparent intact epithelium (Figure 1A-C). Black wavy lines indicate areas containing fast acid-positive bacteria; black arrows indicate PMNs, and red arrow indicates lymphocytes.