TABLE 1.

Cell yield from lungs of I/St mice before and after challenge^a

Infection dose (CFU)	Cell yield (106/mouse)
	2 wk postinfection				5 wk postinfection
	Total	CD3+	CD4+	CD8+	Total	CD3+	CD4+	CD8+
0 (control)	1.2 ± 0.2	0.8 ± 0.2	0.5 ± 0.1	0.3 ± 0.1
103	1.8 ± 0.3	1.0 ± 0.2	0.6 ± 0.1	0.4 ± 0.1	1.8 ± 0.4	1.2 ± 0.4	0.7 ± 0.2	0.6 ± 0.2
105	5.0 ± 1.4	2.8 ± 0.6	1.4 ± 0.5	1.0 ± 0.2	4.5 ± 1.8	2.6 ± 0.3	1.5 ± 0.3	1.2 ± 0.2

^aCells were obtained by enzymatic disruption from lungs of three mice in each group, pooled, enriched for T cells by sequential plastic and nylon wool passages, and counted (total). Percentages of CD3⁺, CD4⁺, and CD8⁺ cells were estimated by flow cytometry, and the yield of corresponding T-cell subsets was calculated. The yield of TCRαβ⁺ cells (not shown) never differed from that of CD3⁺ cells by more than 2%. Values are means from three independent experiments ± standard errors. Values which differ significantly from those for naive mice are in bold (P < 0.05 as determined by Student’s t test and Wilcoxon’s U criterion).