FIG. 1.

Adaptive immunity limits H. influenzae colonization. The density of the H. influenzae strain indicated in the upper respiratory tract lavage fluid of BALB/c WT (circles) and SCID (triangles) mice was determined at 3 days (A) and 14 days (B) post-intranasal inoculation. Bacterial strains included Hib with or without PC expression, NTHI-1 strain TN106.P2, NTHI-2 strain SR7332, and NTHI-3 strain 86.028NP. The log CFU/ml of each H. influenzae strain in the lavage fluid is indicated for each mouse, and horizontal bars denote mean values. The dashed line indicates the limit of detection. Statistical differences were determined using the Mann-Whitney test (*, P < 0.05; **, P < 0.01).