TABLE 1.

Examples of the appearance of CD4⁺ CD8⁺ cells in the lungs during intranasal infection of mice with C. pneumoniae or influenza A virus

Mouse strain	No. of mice	Infectious agenta	No. of days after infection	IFU/sampleb	EID50/mlc	% CD4+ CD8+ cellsd
NIH/S	56	C. pneumoniae	0	<4		2
	7		9	1,714		10
	7		17	<4		70
	7		24	<4		21
	7		42	<4		67
BALB/c	6	C. pneumoniae	0	<4		0
	4		4	29,534		0
	4		8	28,818		10
	4		18	208		0
C57BL/6	5	C. pneumoniae	2	865		1
	5		6	31,197		0
	5		12	41,162		0
	5		27	7		0
NIH/S	6	Influenza A virus	2		130,000	42
	6		4		3,200	33
	5		7		1,000	<1

^aThe infectious doses were 1.5 × 10⁶ IFU of C. pneumoniae for NIH/S and BALB/c mice, 1 × 10⁶ IFU of C. pneumoniae for C57BL/6 mice, and 2 × 10⁴ EID₅₀ of influenza A virus for NIH/S mice. 

^bGeometric means calculated from individual mice in each experiment. 

^cGeometric means calculated from individual mice in two to three experiments. 

^dAnalysis of cells isolated from a pool of lungs; lymphocytes were gated by forward- and side-scatter in fluorescence-activated cell sorter analysis.