CALB1 and Balkan nephropathy: Immunofluorescence staining of lotus tetragonolobus lectin (LTL) (a proximal tubule marker), calbindin D28k (a distal tubule marker), aquaporin-3 (a collecting duct marker), and PSTPIP2 was performed to explore the location of PSTPIP2 in the setting of AAI-induced AAN or to identify the segments of the nephron with PSTPIP2 expression.