Recently new studies have investigated the links among virus infections, upper and lower airway responses, and systemic immunological changes. To circumvent the problems associated with differing serotypes and viral strains, varying pathogenicity of wild-type viruses, and host characteristics, experimental viral cold disease programs have been initiated. This has made it possible to control important virus and host variables, obtain tissue samples from the upper and lower airway, measure airway responsiveness (AR) at set time points, and
Cu"ent affiliations: *University of Stellenbosch, Cape Town, South Africa. tRoyal Brisbane Hospital, Brisbane, Australia.