Delayed hypersensitivity to Newcastle disease virus in high and low interferon-producing mice.

Since it was previously shown that IFN, under certain conditions, can stimulate sensitization to SRBC, we examined the intensity and duration of DH to NDV in high and low IFN-alpha and -beta producing mice that carried either the h or I allele at the If-1 locus. In C57BL/6 mice (If-1h) DH to NDV is of higher intensity and longer duration than in BALB/c (If-1l). Evidence that this difference is related to the higher IFN-alpha and -beta production induced by NDV in C57BL/6 mice was obtained by comparing DH to NDV in C57BL/6 (If-1h) mice and in mice of three congenic strains, carrying the If-1l allele on a C57BL/6 background (B6.C-H-28c-If-1l). In the latter, DH to NDV was much more of BALB/c than of C57BL/6 type, since after footpad challenge a significant reaction was only observed at 24 hr and no longer at 48 hr. When the low endogenous IFN production of the If-1l congenic mice was compensated for by giving extra IFN-alpha and -beta a few hours after sensitization with NDV, DH was enhanced. If, on the other hand, anti IFN-alpha and -beta globulins were administered to either C57BL/6 or If-1l congenic mice immediately after sensitization with NDV, DH was decreased. These results indicate that, on a C57BL/6 background, the establishment of DH to NDV is influenced by the alleles at If-1, determining the levels of endogenous IFN-alpha and -beta induced by NDV.