A 4-year-old child develops a runny nose and cough. After the cough persists for 2 weeks she exhibits paroxysms of coughing so severe she becomes cyanotic. On physical examination, her temperature is 37.4deg C. Her mouth and pharynx reveal no erythema or swelling. On auscultation of the chest, her lungs show crackles bilaterally. She has spasmodic coughing, with a series of coughs on a single breath, bringing up mucus plugs, followed by labored inspiration. The pathogenesis of her disease most likely results from disabling of which of the following?

Bordetella pertussis is the causative agent for whooping cough. These infections occur infrequently when there is widespread childhood vaccination against this organism. This coccobacillary organism is difficult to culture, and direct fluorescent antibody (DFA) testing is the fastest and most reliable way to diagnose the infection. Nasopharyngeal aspirates and swabs are the best specimens because the organisms attach to ciliated respiratory epithelium. The toxin paralyzes cilia. Complement lysis is most useful against circulating infectious agents. Immunoglobulins that circulate can bind organisms, but secretion is an adaptive immune response taking days to weeks. NK cells attack host cells with MHC signaling turned off by intracellular infectious agents such as viruses. Mycobacterial organisms inhibit phagolysosome formation to reduce their intracellular destruction in macrophages.