Immune System Properties & Barriers (PDF)

26.1 Basic Properties of the Immune System Immunity is the ability of an organism to resist infection. Innate immunity (nonspecific immunity) ^ inborn host defenses against a broad range of pathogens the noninducible ability to recognize and destroy an individual pat...

26.1 Basic Properties of the Immune System Immunity is the ability of an organism to resist infection. Innate immunity (nonspecific immunity) ^ inborn host defenses against a broad range of pathogens the noninducible ability to recognize and destroy an individual pathogen or its products does not require previous exposure to a pathogen or its products  Adaptive immunity – the acquired ability to recognize and destroy a particular pathogen or its products – dependent on previous exposure to the pathogen or its products (specificity) – directed toward an individual molecular component of the pathogen (antigen)  important IEttremely 땐 diflerent - lo0k - - - θ agerny □ Figure 26.1  26.2 Barriers to Pathogen Invasion cod toknow ( ? ) D Natural Host Resistance (Figure 26.2) – Normal Microbiota helps host resist pathogens, particularly on the skin and in the gut (competitive exclusion). – The ability of microbes to cause disease varies between species  Infection site and tissue specificity Quite interesting – Different pathogens invade different tissues. – Routes of infection are crucial (e.g., tetanus is in wounds, while Salmonella is ingested, not vice versa). (Table 26.1) Physical and chemical barriers to infection  Mucosal membranes are coated with a thick layer of mucus.  Stomach acid (low pH) inhibits bacterial growth.  Skin is salty and acidic, limiting bacterial growth.