C571Bl/6 and BALB/c mice have similar neutrophil response to acute Streptococcus pneumoniae sinus infections

Background: Previous investigations have shown that mice with a tendency to ward a T(H)1 or T(H)2 lymphocyte response manifest different reactions to i noculation with the parasite Leishmania major. BALB/c mice (with a tendency for a T(H)2 response) showed evidence of systemic infection, whereas C57Bl /6 mice (with a tendency for a T(H)1 response) showed only a local reaction . Objective: To investigate whether BALB/c and C57Bl/6 mice respond different ly to acute bacterial infection of the sinuses. Methods: We inoculated the nasal cavities of C57Bl/6 and BALB/c mice with S treptococcus pneumoniae (type ATCC59), or with broth as a control. The mice were humanely killed 2,5, 10, and 14 days after inoculation. Their heads w ere fixed, decalcified, and embedded in paraffin blocks. Sections were stai ned with hematoxylin and eosin, and the degree of inflammation was quantifi ed by the number of neutrophils per square millimeter of the sinus mucosa a nd the percentage of the sinus cavity occupied by neutrophil clusters. Results: Both groups of mice showed evidence of inflammation that was signi ficantly greater than controls (P=.01), with no difference between groups. There was a correlation between the number of neutrophils per square millim eter in the sinus mucosa and the percentage of neutrophil clusters (C57Bl/6 mice, r=0.37, P<.001; BALB/c mice, r=0.20, P<.001). In the, infected mice, the number of infiltrating neutrophils was significantly greater (P<.001) in anatomically lower (dependent) areas of the sinuses compared with the up per areas. Conclusion: Unlike leishmaniasis, acute bacterial sinusitis is not affected by the tendency of the host to favor either a T(H)1 or T(H)2 response.