innate immunity 2

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Western University
Microbiology and Immunology
Microbiology and Immunology 2500A/B
John Mc Cormick

INNATE IMMUNITY  Innate immunity is the first line of defense against a pathogen  It is always ready to destroy pathogens and is effective at stopping most at an early stage o Active all the time o Over 90% of pathogens destroyed this way Properties of Innate Immunity  1. Inherited o Born with innate immunity (cells and soluble molecules) o Conserved though evolution  Everyone has same innate immune system (same barriers, cells, soluble molecules)  2. Always initiated when pathogen contacts body  3. Responds immediately o Pathogen usually destroyed before any symptoms  4. No memory o Same immune response to identical pathogen each exposure (non-adaptive) Innate Immune Defenses 1. Barriers  Main barrier = epithelial cells  As long as skin is intact it is a very effective barrier  Mucus is another barrier  Additional barriers:   Anti-microbial enzymes = secreted by activated epithelial cells (natural antibiotics)  They act to destroy the cell wall of pathogen  Commensal bacteria 2. Cells 3. Soluble molecules  First barriers try to block the pathogens entry into tissues  If the pathogen enters the tissue then innate cells and soluble molecules are activated and rapidly eliminate the pathogens that enter  If the innate immune system is unsuccessful then certain innate cells instruct the adaptive immune system to eliminate the pathogen Modes of pathogen entry into the body: 1. Wound on the skinn 2. Ingestion (gets into the GI tract) 3. STDs (through reproductive tract) 4. Breathing (respiratory tract) Antibiotics kill bacteria  They kill the pathogenic bacteria and the bacterial microflora (good bacteria)  They cant distinguish between the two  Commensal bacteria act as another barrier for epithelial cells  they use up nutrients in the area so there are no nutrients for pathogenic bacteria o Antibiotics kill this bacteria too  if you take correct dosage some will be destroyed but not enough to destroy the whole layer o If you overdose you destroy the barrier and leaves the epithelial cells unprotected and then pathogen can gain entry Crohn’s Disease  Inflammatory bowel disease
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