FIG. 5.

Effects of gamma interferon and TNF-α on MHC class I expression by bovine macrophages incubated for 24 h with or without M. avium subsp. paratuberculosis (M. pt) or M. avium subsp. avium. Unlike M. avium subsp. paratuberculosis-infected macrophages, M. avium subsp. avium-infected macrophages upregulated MHC class I molecules in response to gamma interferon and TNF-α. As a positive control, uninfected macrophages were incubated with gamma interferon and killed S. intermedius (Staph) organisms. The mean and SE for three separate experiments are shown. a, statistically significant differences relative to control values (P < 0.05); b, statistically significant differences relative to samples incubated with M. avium subsp. avium organisms alone (P < 0.05).