TABLE 5.

IFN-γ production by T-cell lines established from calves immunized with A. marginale MSP-2 without or with IL-12

Group and animal	IFN-γ (U/ml) produced by T-cell lines stimulated witha:
	Medium	URBC	A. marginale
II
57	NDb	ND	<10
63	ND	ND	236
65	ND	ND	<10
III
59	694	654	1,325
60	1,400	1,413	2,884
61	691	948	1,642

^aT-cell lines were established from antigen-draining (right) LNC and stimulated weekly with antigen and APC for 3 weeks. After being washed, 2 × 10⁶ T cells were cultured in duplicate for 48 h with 2 × 10⁶ APC and either medium or 3 μg of membrane antigen prepared from URBC or A. marginale per ml. Supernatants were analyzed for IFN-γ production by ELISA with bovine IFN-γ as a standard. Values are the mean titers of IFN-γ production for each cell line. The mean titer of IFN-γ produced by cell lines from group III calves (immunized with MSP-2 and IL-12) is significantly greater (P < 0.05) than that produced by cell lines from group II calves (immunized with MSP-2), as analyzed by the one-tailed, nonpaired Student's t test for samples with unequal variance. APC cultured with antigen produced <1 U of IFN-γ per ml. 

^bND, not determined.