Pathways stimulated by microbes and their associated molecular patterns in oral (A) and airway (B) epithelial cells leading to β-defensin expression. These models are based solely on published studies demonstrating the role of the respective receptors, adapter molecules, and transcription factors. In some cases, e.g., stimulation of hBD-2 by P. intermedia, specific stimulatory molecule, receptor, pathway, and/or transcription factors have not been identified, and are shown as a question mark.