(a, b) C57BL/6 mice were uninfected or infected with N. brasiliensis. Twenty-three days later, mice were challenged intratracheally with PBS or HDM (25 μg in PBS) daily for 3 consecutive days. 24h after the last challenge, BAL fluids and lungs were collected and analyzed. N.b., N. brasiliensis only; HDM, HDM challenge in uninfected mice; N.b.+HDM, HDM challenge 23 days after N. brasiliensis infection; N.b.+HDM+anti-MHCII, 500 μg anti-MHCII antibody was injected i.v. on day 1 and day 3 of HDM challenge. Percentages shown were calculated as a percent of the live cells. ****P<0.0001; **, P<0.01; ***, P<0.001; *, P<0.05; ns, not significant, P>0.05. (c) Lung histology analysis. Top 3 panels, lung sections were stained with H&E; left panel arrow - mucus metaplasia; center panel arrow - perivascular infiltration; right panel arrow - alveolar infiltration. Lower left panel, PAS staining arrow - mucus metaplasia; lower middle, Luna staining arrow - eosinophils; and lower right, Ym1 staining arrow – Ym1+ macrophages. Data are representative of two (a, c) or three (b) independent experiments with 3–4 mice in each group.