TABLE 2.

Flow cytometric analysis of pulmonary CD4⁺ lymphocytes expressing IFN-γ, IL-4, or both from mice infected with wt RSV or rRSV/mIL-2^a

Virus	Day 4			Day 10b			Day 32			Day 38
	IFN-γ+	IL-4+	Dbl+	IFN-γ+	IL-4+	Dbl+	IFN-γ+	IL-4+	Dbl+	IFN-γ+	IL-4+	Dbl+
rRSV/mIL-2	3.3 ± 0.32	0.99 ± 0.21	0.20 ± 0.06	8.8 ± 1.10*	2.4 ± 0.09**	0.61 ± 0.01**	1.3 ± 0.34	0.78 ± 0.12	0.04 ± 0.02	20 ± 3.83	0.56 ± 0.07	0.22 ± 0.06
wt rRSV	2.7 ± 0.66	0.95 ± 0.28	0.14 ± 0.05	4.2 ± 1.11	0.65 ± 0.18	0.15 ± 0.06	4.1 ± 0.66	1.1 ± 0.28	0.09 ± 0.04	19.3 ± 1.35	0.43 ± 0.05	0.14 ± 0.00
None (mock)	0.48 ± 0.03	0.28 ± 0.00	0.03 ± 0.00	1.7 ± 0.25	1.1 ± 0.21	0.31 ± 0.10	ND	ND	ND	5.8 ± 0.10c	0.70 ± 0.14c	0.10 ± 0.02c

^aMice were infected intranasally on day 0 with 10⁶ PFU of the indicated virus per animal or were mock infected. Animals from each group were sacrificed on days 4 and 10, as indicated. The remaining animals (including the mock-infected group) were challenged on day 28 with 10⁶ PFU of wt RSV per animal, and the animals were sacrificed on days 32 and 38 (4 and 10 days postchallenge) as indicated. Total pulmonary mononuclear cells were analyzed by flow cytometry using immunostaining for CD4, IFN-γ, and IL-4. Values are expressed as the percentage of CD4⁺ lymphocytes. Each group contained four mice per day with the following exceptions: the wt RSV group on day 4 had three animals, the mock-infected group on day 4 had two animals, and the mock-infected group on days 10 and 38 had three animals each. The cells of each animal were processed separately, and each group is expressed as the mean of the individual data for the two to four mice with the standard error indicated. Dbl⁺, doubly positive (IFN-γ⁺ and IL-4⁺); ND, not determined. 

^bStatistical significance calculated by Student's t-test compared to that of wt rRSV control: ∗, P < 0.005; ∗∗, P < 0.001. 

^cNote that the animals in the Mock group were mock infected on day 0 but received the RSV challenge on day 28. Hence, the day 38 point corresponds to the day 10 point for the wt RSV group.