Non-specific and specific immunity to bacterial invasion of the middle ear cavity.

The role of the non-specific (mucociliary clearance, mucus, lactoferrin, lysozyme, fibronectin, lactoperoxidase, complement, phagocytosis) and specific (immunoglobulins) immune systems in combating bacterial pathogens invading the middle ear cavity is discussed. The non-specific system is present from birth, acts promptly against a broad spectrum of microorganisms, has no memory, and is present for life. In contrast, immunoglobulins act specifically. Secretory IgA antibody prevents bacteria from attaching to the epithelium, has no pro-inflammatory effect and does not activate complement. IgG antibodies can opsonize the bacteria for phagocytosis and eventually prevent the bacteria from penetrating the epithelium. IgG is pro-inflammatory and can activate a complement cascade.