Kidney histology. Representative sections of renal cortex from NZB × NZW F1 female mice. (a) Section of kidney with glomeruli (arrows) and tubules that are within normal limits from a 12-week-old mouse. (b) Section from an untreated 36-week-old mouse. Glomeruli (arrows) are small with markedly thickened basement membranes and decreased numbers of cells (glomerulosclerosis). Tubules are dilated and contain protein casts or droplets in the lumens. (c) Section from a 36-week-old mouse treated with sirolimus has kidneys that are within normal limits. Glomerular (arrows) basement membranes are slightly thicker than those in the untreated 12-week-old mice. H & E, 40× original magnification.