Mast cells protect against airway Mycoplasma pneumoniae under allergic conditions


Richard J. Martin, 1400 Jackson Street, Denver, CO 80206, USA.


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.