Role of Surfactant Protein-A in Nitric Oxide Production and Mycoplasma Killing in Congenic C57BL/6 Mice

We generated congenic surfactant protein A (SP-A)–deficient (SP-A[−/−]) mice on the mycoplasma resistant C57BL/6 background (B6.SP-A[−/−]) and characterized their response to mycoplasma infection in comparison to C57BL/6 (B6) mice. B6.SP-A(−/−) mice infected with 106 colony-forming units (cfu) of Mycoplasma pulmonis had significantly higher bacterial lung loads than B6 mice at 72 h postinfection (p.i.). At the higher infection dose of 107, B6.SP-A(−/−) mice had significantly higher lung cfu at 24 h; however, no difference in mycoplasma cfu was observed between B6 and B6.SP-A(−/−) mice at 48 and 72 h p.i. We found that uninfected B6 mice had lower bronchoalveolar lavage nitrite (NO2−) and nitrate (NO3−) levels as compared with B6.SP-A(−/−) mice. On the other hand, infection of B6 mice with mycoplasmas resulted in significantly higher bronchoalveolar lavage NO2− and NO3− as compared with B6.SP-A(−/−) mice. These data indicate that SP-A may help regulate NO production in response to a specific stimulus, i.e....