FIG. 1.

Microscopy of human nasopharyngeal explants. Immunohistochemistry of control explant (a) and explant infected for 72 h with influenza B virus (b). The latter shows strong signal from individual sustentacular cells, in contrast to absent staining in the control section. (c) Scanning electron micrograph of human nasopharyngeal explant incubated with PBS as a control for 48 h and superinfected with N. meningitidis for 24 h; bacteria are seen in association with nonciliated epithelial cells (original magnification, ×2,500). (d) Transmission electron micrograph of an explant treated similarly to that shown in panel c. Bacteria are seen adhering to the epithelial surface (bar = 10 μm).