The critical role of the local immune response in infection control

Abstract

Microbes are able to survive on animal and plant products by releasing digestive enzymes directly and absorbing the nutrients, and/or by growth on living tissues (extracellular), in which case they are simply bathed in nutrients. Other microbes infect (invade and live within) animal/human cells (intracellular), where they not only survive, but also replicate utilizing host-cell  sources. 

The immune system protects us from attack by various microbes. It uses  well specialized organs in order to respond to microbes entering the body’s tissues. Molecules and cells respond rapidly to attack. Healthy individuals  (i.e. immunocompetent) have many distinct  molecules, innate immunity cells  and lymphocytes, each of which is specific for a different clonal selection foreign substance (antigen).

Mucosal  and skin immune responses provide local protection against infection, without inducing excessive amounts of inflammation that would alter epithelial integrity or function.  The skin is not a simple   sheath made of several layers of cells but has the functions of a dynamic organ/system with cells and molecules which are activated when the tissue is under attack. Interaction of skin immunity with systemic response  is essential to avoid dysregulations associated with inflammatory disease. In addition  the mucosal immune system provides protection against  pathogens and maintains a tolerance towards non-harmful commensal microbes and benign environmental substances.

MALT (mucosa-associated lymphoid tissue)  provides the organism with an important first line of defense. Many data support the concept of  MALT (including  gut, lung, mammary gland, salivary and lacrimal glands, and genital tract) as a general system  reacting to an immunogen at a mucosal site and producing immunity at distant sites.