Innate immunity and pulmonary host defense

Abstract

The lung, in order to facilitate gas exchange, represents the largest epithelial surface area of the body in contact with the external environment. As normal respiration occurs, the upper and lower airways are repeatedly exposed to a multitude of airborne particles and microorganisms. Since these agents are frequently deposited on the surface of the respiratory tract, an elaborate system of defense mechanisms is in place to maintain the sterility of the lung. Innate defenses are primarily responsible for the elimination of bacterial organisms from the alveolus. Early bacterial clearance is mediated by a dual phagocytic system involving both alveolar macrophages and polymorphonuclear leukocytes. The recruitment and activation of inflammatory cells at a site of infection involves the orchestrated expression of leukocyte and vascular adhesion molecules, as well as the establishment of chemotactic gradients via the generation of proinflammatory cytokines and chemokines. Immunologic manipulation of innate immunity may serve as an important adjuvant therapy in the treatment of both immunocompromised and immunocompetent patients with severe lung infections. As the complexities of the host-pathogen interaction are further dissected and elucidated, it is likely that the therapeutic benefits from these approaches will be realized.

Early granuloma formation after aerosol Mycobacterium tuberculosis infection is regulated by neutrophils via CXCR3‐signaling chemokines

“…After aerosol infection with Mycobacterium tuberculosis, PMN migrate to the lung tissue and the alveolar space within a few hours (reviewed in [3][4][5]). However, current knowledge about the contribution of PMN to the control of tuberculosis remains controversial.…”

Toll-Like Receptor 2 Plays a Role in the Early Inflammatory Response to Murine Pneumococcal Pneumonia but Does Not Contribute to Antibacterial Defense

“…The first line of defense against invading bacteria is provided by the innate immune system, which recognizes pathogen-associated molecular patterns (PAMPs), 3 conserved microbial patterns shared by large groups of pathogens, but not found in higher eukaryotes (7)(8)(9). Over the last few years, it has become evident that both the recognition and the subsequent response to pathogens is mainly transferred by members of the Toll-like receptor (TLR) family (for review, see Refs.…”

Broadening Our View About the Role of Mycobacterium tuberculosis Cell Envelope Components During Infection: A Battle for Survival

“…In the bronchoalveolar lavage fluid, they normally represent less than 2% of all cells, however, during inflammation a massive influx of neutrophils occurs (Mizgerd, 2002;P. Zhang et al, 2000).…”

“…Zhang et al, 2000). Neutrophils eliminate microbes by a number of oxidative and nonoxidative mechanisms (P. Zhang et al, 2000) including secreted hydrolases such as N-acetyl--glucosaminidase, -glucuronidase, -mannosidases, and lysozyme. Neutrophils can kill M.tb through both oxidative and non-oxidative processes (Brown et al, 1987;Jones et al, 1990).…”