257.A 14-year-old girl presents in the pediatric nephrology clinic with
fatigue, malaise, anorexia, abdominal pain, and fever. She reports a loss of
6 lb in the last 2 months. Serum gamma globulin as well as the immunoglob-
ulins: IgG, IgA, and IgM are all elevated. She is diagnosed with bilateral pho-
tophobia as a result of nongranulomatous uveitis. Her serum creatinine is
1.4 mg/dL (normal: 0.6 to 1.2 mg/dL) and urinalysis of glucose and protein
are 2+on dipstick test and are confirmed by the laboratory at 8.0 g/dL and
0.95 g/dL, respectively. A renal biopsy is prepared for light and electron
microscopy. Lymphocytes, plasma cells, and eosinophils are found within
infiltrates with pathological change in the tubular basement membrane. The
cell most affected is shown in the accompanying transmission electron
micrograph. Which of the following is a correct statement about this cell?
388 Anatomy, Histology, and Cell Biology
a. Impermeable to water despite the presence of ADH
b. The site of the countercurrent multiplier
c. The site of action of aldosterone
d. The source of renin
e. The primary site for the reduction of the tubular fluid volume