Mycoplasma pneumoniae can exacerbate asthma, and recent evidence indicates that a subset of patients with chronic asthma are polymerase chain reaction positive for the organism and show marked improvement on treatment with clarithromycin. We examined the interactions of the organism with surfactant protein (SP)-A and SP-D, two bronchoalveolar proteins that are potent modulators of the innate immune response. SP-A and SP-D are pattern recognition molecules, and their effects on innate immunity can be either positive or negative depending on the activation state of the target cell and the nature of the microbial ligand. SP-D binds intact mycoplasma and membranes derived from the organism with high affinity (apparent dissociation constant = 7.0 nmol/L). Characterization of the ligands present in membranes reveals that several glycolipid species are recognized by SP-D. SP-A also binds mycoplasma membranes with high affinity (apparent dissociation constant = 0.3 nmol/L), and the ligands are lipids that are different from those bound by SP-D. Macrophages respond to intact mycoplasma and derived membranes by secreting tumor necrosis factor-α and nitric oxide. Purification and characterization of the major macrophage activation factor from mycoplasma reveals that it is a membrane lipoprotein that acts through Toll-like receptor 2. SP-A enhances the response of macrophages to mycoplasma membranes and lipoprotein preparations by increasing the tumor necrosis factor-α response threefold and the nitric oxide response 2.5-fold. These findings indicate that mycoplasma can potentially promote inflammation in the lung by binding SP-D and neutralizing its anti-inflammatory effects, and by interacting with SP-A and macrophages and enhancing the release of proinflammatory mediators.