Role of innate immunity in respiratory mycoplasma infection

Mycoplasmas are unique among respiratory pathogens. They possess very small genomes, lack cell walls and are strictly dependent on the host for survival. These pathogens have developed the ability to quickly adapt to the host environment through attachment to target cells within the host. Mycoplasmas have been identified as commensal microbial flora of healthy persons yet, infection of the upper and lower respiratory tracts can result in acute cough, fever and headache, and even chronic disease involving multiple organs. The lung contains a complex system of defense mechanisms with which to combat these pathogens, including innate (nonspecific) and acquired (specific) immune responses. Innate defenses include mechanical clearance, cellular responses provided by host phagocytes and molecular protection in the form of antimicrobial peptides. The interaction of mycoplasmas with different components of the innate immune system and mechanisms by which they incite pathology has proved elusive. The mechanisms by which pathogenic mycoplasmas evade the innate immune system are unknown. The purpose of this review is to summarize current knowledge of these interactions in the hope of identifying new avenues for research and therapy.