**Tropical Lung Diseases**

Ntumba Jean-Marie Kayembe

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/52371

**1. Introduction**

Infectious disease results from the disruption of the balance between the host and the patho‐ gen. Pathogen influencing factors include virulence, immunoevasion capacities, and drug resistance ability. According to the host, disease outcome relay on many factors such as: im‐ munocompetence, comorbidities, terrain (ageing, malnutrition).

The lung epithelium is a large surface exposed to outside aggression. The environment plays a key role in the onset and development of illness by many factors such as: climate, social and cultural habits, vegetations, degree of industrial, or domestic pollutions...

Despite this exaggerated exposition, the lung is nevertheless protected through non specific and/ or specific defense mechanisms (Agostini CV, Chilosi M, Zambello R et *al*, 1993).

## **1.1. Non specific defense mechanisms**

According to its size, a foreign substance can reach the upper or lower respiratory tract, and be cleaned via the mucociliary escalator, during coughing or sneezing. Epithelial cells also secrete many agents such as lysozyme, toxic oxygen radicals, with antimicrobial properties. The renewal of the epithelium, as for the skin, is an additional protecting property.

Innate immune recognition is a second protective mechanism implicating immune cells and secreted mediators. Its under the control of cells carrying receptors for recognition of foreign antigens (PRRs: pathogen recognition receptors) such as macrophages, dendritic cells, neutrophils, mastocytes, epithelial cells, NK cells, and fibroblasts which can link mi‐ crobial structures (PAMPS: pathogen associated molecular patterns) for further destruc‐ tion (Ahnen DJ, 1985).

© 2013 Kayembe; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
