THE LEWIS blood group antigens Lea and Leb have been found on red blood cells (RBCs), in secretions and fluids such as saliva, alimentary tract juice, and urine, and in various tissues including renal tubular cells, collecting ducts, urothelium, and ductal or mucosal epithelium of the sweat glands, salivary glands, gastrointestinal tract, pancreas, uterus, cervix, and breast. l .s Hepatic bile ...