TABLE 3.

Intracellular staining for IFN-γ production by lymphocyte subsets in response to mycobacterial antigen stimulation

Treatmenta	IFN-γ production by subset:
	Ungatedb	CD4+	CD8+	γδ TCR+
No stimulation	1.07 (0.49)	0.51 (0.22)	0.34 (0.22)	0.11 (0.11)
WCS stimulation	12.16 (4.57)*	9.65 (3.27)**	0.92 (0.44)	0.63 (0.16)
PPDa stimulation	7.10 (2.65)	3.92 (1.10)	0.97 (0.71)	0.68 (0.32)

^aAt 313 days postchallenge, PBMC were cultured with either medium alone, 5 μg of PPDa/ml, or 10 μg of strain 19698 WCS (WCS/ml) for 7 days (ionomycin, PMA, and brefeldin A added for the terminal 5 h), harvested, and analyzed by flow cytometry for phenotype and intracellular IFN-γ by flow cytometry. Data are presented as mean (±SEM, n = 3) percent of cells staining positive for IFN-γ.

^bUngated refers to the response of the total live PBMC population. Differs (*, P = 0.07; **, P < 0.05) from nonstimulated samples, same subset (i.e., vertical comparisons within group). Responses were not detected for samples obtained from noninfected animals of the same sex, age, breed, and herd of origin as infected animals (data not shown; n = 3).