TABLE 3.

IFN-γ responses to SEB, PPDb, and PPDj in whole-blood cultures of fresh (8-h-old) or day-old samples^a

Stimulus concn (μg/ml)	IFN-γ response of cow:
	1031			1053			1075			1089			1101			1104			1112			1122
	SEB	PPDb	PPDj	SEB	PPDb	PPDj	SEB	PPDb	PPDj	SEB	PPDb	PPDj	SEB	PPDb	PPDj	SEB	PPDb	PPDj	SEB	PPDb	PPDj	SEB	PPDb	PPDj
Day 1
1	3.16			3.11			2.25			1.18			2.87			1.89			3.17			1.75
2.5		0.13	0.64b		0.16	0.81b		0.01	0.02		0.08	0.05		0.78	1.58b		0.02	0.44b		1.07	1.65b		0.02	0.25b
5		0.21	0.46b		0.17	0.64b		0.02	0.05		0.02	0.05		0.38	1.77b		0.04	0.27b		1.22	2.10b		0.04	0.31b
10		0.30	1.58b		0.24	0.74b		0.01	0.16b		0.02	0.11b		0.48	2.05b		0.05	0.38b		1.43	2.81b		0.06	0.38b
20		0.34	1.85b		0.22	0.87b		0.04	0.13b		−0.02	0.10b		0.59	2.22b		0.07	0.44b		1.53	2.96b		0.08	0.40b
40		0.20	2.07b		0.16	0.96b		0.05	0.16b		−0.03	0.14b		0.54	2.25b		0.08	0.53b		1.51	3.07b		0.09	0.47b
Day 2
1	3.02			0.92			1.69			0.77						1.23			1.07			0.88
2.5		0.02	0.62b		0.00	0.28b		0.00	−0.01		−0.04	0.04					0.01	0.09		0.13	0.24b		0.01	0.03
5		0.02	0.52b		0.02	0.09		−0.02	0.00		0.01	−0.07					0.01	0.06		0.20	0.46b		0.01	0.06
10		0.06	0.59b		0.06	0.14b		−0.01	0.01		0.01	0.01					0.02	0.08		0.26	0.69b		0.01	0.08
20		0.07	0.63b		0.05	0.19b		−0.01	0.03		−0.06	0.06					0.02	0.09		0.28	0.82b		0.02	0.09
40		0.06	0.70b		0.06	0.15b		−0.01	0.03		−0.18	−0.18					0.04	0.10b		0.30	0.90b		0.04	0.11b

^aAll results are expressed as the OD of stimulation − no-antigen (PBS) stimulation. Three additional animals produced IFN-γ levels with PPD-PBS of <0.1 in all stimulations (positive control [SEB] >1.5) and were omitted from the table.

^bPositive test result for paraTB by the IDEXX criterion: PPDj-PBS >0.100 and PPDb-PPDj < 0.71.