Table 1. cSiO₂ exposure increases severity of lymphocytic cell infiltration in lungs of NZBWF1 mice relative to C57Bl/6 mice.

Histopathological Lesion	cSiO2 dose
	NZBWF1			C57Bl/6
	0.0 mg	0.25 mg	1.0 mg	0.0 mg	1.0 mg
Lymphocytic cell infiltration	0.8 ± 0.2	2.5 ± 0.3*	3.4 ± 0.2*, b	0.0 ± 0.0	2.3 ± 0.2*, a
Alveolitis	0.0 ± 0.0	1.5 ± 0.2*	2.5 ± 0.3*, a	0.0 ± 0.0	2.3 ± 0.3*, a
Alveolar proteinosis	0.0 ± 0.0	1.4 ± 0.2*	2.6 ± 0.2*, a	0.0 ± 0.0	2.6 ± 0.2*, a

Mice were graded individually for severity of lung inflammation (% of total pulmonary tissue examined) as follows: 0, no changes; 1, minimal (<10%); 2, slight (10–25%); 3, moderate (26–50%); 4, severe (51–75%) 5; very severe (>75%) of total area affected. Data are mean ± SEM (n = 8/gp). NZBWF1 mice were analyzed by One-way ANOVA on Ranks followed by Spearman rank-order correlation. C57Bl/6 mice were analyzed by Mann-Whitney Rank Sum Test. Comparisons between strains at 1.0mg cSiO₂ were analyzed for statistical differences by Mann-Whitney Rank Sum Test. Asterisks indicate statistical difference between silica treatment and vehicle control (p < 0.05). Different letters indicate statistical difference in histopathological lesions between strains (p < 0.05). cSiO₂ dose in NZBWF1 significantly correlated (p < 0.05) with lymphocytic cell infiltration (Spearman rank-order correlation coefficient = 0.87), alveolitis (Spearman rank-order correlation coefficient = 0.90), and alveolar proteinosis (Spearman rank-order correlation coefficient = 0.94)