Histology of BALB/c and C57BL/6 mouse lung after OVA sensitization and 3 days of aerosolized OVA challenge. Both strains show an inflammatory response around the bronchovascular bundles after 3 OVA challenges (arrows), the routine time for assessment of lung MCp's. The lung from the BALB/c mouse (left panel) shows much more leukocyte infiltration than does the lung from the C57BL/6 mouse (right panel).