Interferon and delayed-type hypersensitivity to a viral antigen.

Delayed hypersensitivity to Newcastle disease virus was measured with use of a footpad test in mice. When tissue culture interferon was administered 24 hr before sensitization, footpad swelling upon subsequent challenge with the virus was significantly decreased. In animals already sensitized to the virus, footpad swelling was similarly decreased if interferon was administered a few hours before footpad challenge. This result indicates that interferon can affect both the afferent and the efferent pathways of delayed hypersensitivity to Newcastle disease virus and is in agreement with previous results obtained with nonviral antigens.