Uroplakins Ia and Ib (special tetraspanins) specifically bind with their associated (non-tetraspanin) uroplakins II and IIIa, and together form two dimensional crystals of 16 nm particles, known as urothelial plaques, which cover almost the entire apical surface of the mammalian bladder urothelium, modulating the urothelial permeability barrier [45, 46], and are involved in urinary tract infection [47]. This evidence concerns the gene UPK2 and urinary tract infection.