Abstract
Electron microscopy of cerebral tissue in a human case of herpes-simplex encephalitis revealed tubular structures within the endoplasmic reticulum of endothelial cells and macrophages. These structures were morphologically identical to those recently described in kidney tissue in lupus erythematosus and a variety of other renal diseases. In addition, their size, relation to endoplasmic reticulum and occurrence within endothelial cells suggest that they are similar if not identical to crystalline aggregates described in a variety of neoplasms and infections, including herpes-simplex encephalitis in animals. Though these particles have been regarded as viral or virus-like in nature, consideration of their morphologic features and their distribution in many conditions suggests that they represent a cellular host response whose widespread occurrence has not been sufficiently appreciated.