TABLE 2.

Effects of in vitro infection with live M. avium subsp. paratuberculosis on IFN-γ production in cell culture supernatants from healthy cows and cows with subclinical or clinical Johne's disease

Disease status of cow (no. of cows)	M. paratuberculosis infection	Concn of IFN-γ produced (ng/ml) (mean ± SEM)a
		8 h	3 days	6 days	Avgb
Healthy (5)	No	0.40 ± 0.17 *†	0.06 ± 0.04 *	0.89 ± 0.49 †	0.45 ± 0.19 A
	Yes	0.92 ± 0.38 *	4.85 ± 2.00 *	8.73 ± 2.74 †	4.83 ± 1.40 C
Subclinical disease (4)	No	3.20 ± 1.03 *	1.44 ± 0.87 *	2.36 ± 1.66 *	2.33 ± 0.68 BD
	Yes	2.96 ± 0.26 *	3.36 ± 0.88 *	4.05 ± 2.00 *	3.45 ± 0.68 BC
Clinical disease (5)	No	2.91 ± 0.32 *	1.16 ± 0.34 †	0.72 ± 0.45 †	1.60 ± 0.32 D
	Yes	5.26 ± 0.73 *	6.79 ± 1.49 *	4.84 ± 1.73 *	5.63 ± 0.77 C

^aPBMC culture medium was replaced with complete medium on day 6. On day 7 (18 h later), cells in culture were stimulated with live M. avium subsp. paratuberculosis at a bacterium-to-adherent cell ratio of 10:1. Culture supernatants were collected at 8 h, 3 days, and 6 days after in vitro infection and analyzed by an ELISA. The different symbols after the values indicate statistically significant differences over time (P < 0.05) (values with the same symbol were not significantly different).

^bValues in the Avg column are the mean concentration of IFN-γ produced for all time points in the medium control supernatants with or without in vitro infection with M. avium subsp. paratuberculosis by cells from healthy, subclinically infected, and clinically infected cows. The different letters after the values indicate statistically significant differences between the values for the treatment groups (P < 0.05) (values with the same letter were not significantly different).