rhIL-15 administration is associated with an enlarged liver with normal hepatocytes, but with the presence of leukocytes including lymphocytes and neutrophils in the liver sinusoids. Left panel is the liver histology of an animal receiving vehicle control for 12 days with a necropsy on day 13. Center panel is the liver histology of an animal receiving 50 μg/kg/d for 12 days, with necropsy at day 13, showing normal hepatocytes but the presence of leukocytes including lymphocytes and neutrophils in the liver sinusoids. Right panel is the liver histology of an animal receiving 50 μg/kg/d of rhIL-15 for 12 days with necropsy at day 44, showing a return toward a normal pattern.