Background Infection with Mycoplasma pneumoniae (Mp) in asthma can occur both acutely and chronically with an associated Th2 inflammatory response and/or increased numbers of bronchial mast cells. Mast cells have previously been shown to promote mycoplasma clearance in mice; however, it is unknown whether mast cells would aid Mp clearance under allergic conditions.
Objective Our aim was to determine the impact of allergic inflammation on mast cell-mediated lung Mp clearance. Furthermore, as we have previously demonstrated an essential role for IL-6 in lung Mp clearance we also investigated the role of mast cell-derived IL-6.
Methods Mast cell-deficient (WBB6F1/J-KitW/KitW-v) mice were challenged with ovalbumin to induce airway inflammation before Mp infection. The role of mast cell-derived IL-6 in bacterial clearance was further investigated by reconstitution of mast cell-deficient mice with IL-6−/− mast cells.
Results Allergic mast cell-deficient mice exhibited increased lung Mp burden compared with control littermates. Intravenous adoptive transfer of wild-type and IL-6−/− mast cells significantly improved Mp clearance in mast cell-deficient mice. Acutely after Mp infection, allergen-challenged mast cell-deficient mice had increased levels of the pro-inflammatory cytokines IL-6 and TNF-α in the bronchoalveolar lavage (BAL) fluid. The total number of neutrophils was also increased in mast cell-deficient mice.
Conclusions Our results establish that mast cells aid host defense against Mp in an allergic setting and that while IL-6 is necessary for lung Mp clearance, mast cell-derived IL-6 is not required.
Cite this as: N. M. Michels, H. W. Chu, S. C. LaFasto, S. R. Case, M. N. Minor and R. J. Martin, Clinical & Experimental Allergy, 2010 (40) 1406–1413.