FIG. 2.
Immunohistochemistry of autopsy lung specimens from a 15-month-old patient with an untreated RSV infection (72). Immunostaining for RSV antigens (a) revealed infection of the bronchiolar epithelium in a near circumferential pattern sparing the basal cells. The basal cells can restore the epithelium, but in the process may lead to mucus metaplasia and remodeling of airways. In addition to infection of the polarized ciliated epithelium, it appears that other cell types, potentially including intraepithelial DCs, can be infected (arrows point to the projections of irregularly shaped RSV-infected cells that are thought to be DCs, based on morphology). Immunostaining for CD1a+ DCs (b) showed that they are not prominent in the lung parenchyma during infection, but when present can have a distinctive morphology with multiple projections that can extend beyond the apical or basal boundary of the columnar epithelium. CD69+ monocytes were the major cell type present in peribronchiolar infiltrates. However, CD3+ T cells also were abundant and, while most of them appeared to be double negative for CD4 and CD8, many were positive for CD8 immunostaining (c). In panels a to c, L indicates airway lumen; in panel c, the lower lumen is occluded with debris and immune cells.