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699792 
Journal Article 
Mast cells protect mice from Mycoplasma pneumonia 
Xu, X; Zhang, D; Lyubynska, N; Wolters, P; Killeen, N; Baluk, P; McDonald, D; Hawgood, S; Caughey, G 
2006 
Yes 
American Journal of Respiratory and Critical Care Medicine
ISSN: 1073-449X
EISSN: 1535-4970 
173 
2 
219-225 
English 
16210667 
As the smallest free-living bacteria and a frequent cause of respiratory infections, mycoplasmas are unique pathogens. Mice infected with Mycoplasma pulmonis can develop localized, life-long airway infection accompanied by persistent inflammation and remodeling.

Because mast cells protect mice from acute septic peritonitis and gram-negative pneumonia, we hypothesized that they defend against mycoplasma infection. This study tests this hypothesis using mast cell-deficient mice.

Responses to airway infection with M. pulmonis were compared in wild-type and mast cell-deficient Kit(W-sh)/Kit(W-sh) mice and sham-infected control mice.

Endpoints include mortality, body and lymph node weight, mycoplasma antibody titer, and lung mycoplasma burden and histopathology at intervals after infection. The results reveal that infected Kit(W-sh)/Kit(W-sh) mice, compared with other groups, lose more weight and are more likely to die. Live mycoplasma burden is greater in Kit(W-sh)/Kit(W-sh) than in wild-type mice at early time points. Four days after infection, the difference is 162-fold. Titers of mycoplasma-specific IgM and IgA appear earlier and rise higher in Kit(W-sh)/Kit(W-sh) mice, but antibody responses to heat-killed mycoplasma are not different compared with wild-type mice. Infected Kit(W-sh)/Kit(W-sh) mice develop larger bronchial lymph nodes and progressive pneumonia and airway occlusion with neutrophil-rich exudates, accompanied by angiogenesis and lymphangiogenesis. In wild-type mice, pneumonia and exudates are less severe, quicker to resolve, and are not associated with increased angiogenesis.

These findings suggest that mast cells are important for innate immune containment of and recovery from respiratory mycoplasma infection.