Biopsies from human kidney transplants with acute T-cell–mediated rejection are characterized by high tubular C3a production and IL-17 infiltration. Histology samples from acutely rejecting (top panels) and nonrejecting (bottom panels) kidney transplants were stained with indicated Abs and analyzed by confocal fluorescence microscopy. Results shown are representative of histology data obtained from samples of 3 patients with acute kidney rejection and 2 patients without signs of kidney rejection (×60 magnification for the 8 large panels, and ×100 magnification for the inset). ctrl, control; FITC, fluorescein isothiocyanate; H&E, hematoxylin and eosin; TRITC, tetramethylrhodamine isothiocyanate.