Electron microscopy of the Arthus reaction, using ferritin as antigen.

Arthus lesions were produced in skin and striated muscle of guinea pigs and rabbits sensitized to ferritin. Biopsies of these lesions were then examined with the electron microscope. Electron micrographs of lesions obtained as early as 15 minutes following challenge with antigen demonstrated ferritin surrounded by amorphous material of lesser electron-density comparable to in vitro ferritin-antibody precipitates. Ferritin-anti-body precipitates were widely distributed throughout the lesions and were preferentially localized in and on either side of the basement membranes of small blood vessels.