Innate Immune Response PDF
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Badr University in Cairo
Dr. Amany M. Tawfeik
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Summary
This document provides a detailed description of the innate immune response, covering its components, barriers, cells, and mechanisms. It explains how the innate immune system reacts to invading pathogens, and the processes involved in phagocytosis and other mechanisms. The document also includes learning objectives, references, and a wide range of topics in Immunology, including various cells, molecules, and processes involved in host defense responses to pathogens. The document is designed for academic purposes.
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Innate immune response By Dr. Amany M. Tawfeik Medical Microbiology & Immunology department Learning Objectives: 1- Identify Innate Immune Components/Barriers. 2- Cells of Innate Immunity and their functions. References: 1. First Aid for the USMLE Step 1 20...
Innate immune response By Dr. Amany M. Tawfeik Medical Microbiology & Immunology department Learning Objectives: 1- Identify Innate Immune Components/Barriers. 2- Cells of Innate Immunity and their functions. References: 1. First Aid for the USMLE Step 1 2018. Le Tao, BhushanVikas, Sochat Matthew, ChavdaYash, Zureick Andrew, KalaniMehboob and Kallianos Kimberly. New York: McGraw-Hill Education, 2018. page 109 2. First Aid for the USMLE Step 1 2018.Kaplan Page 1070 Innate Immunity The innate immune system is an important part of any immune response. It is responsible for reacting quickly to invading microbes and for keeping the host alive while the adaptive immune system is developing a very specific response. The innate immune defenses are all present at birth, ready to fight off an infection; they have a very limited diversity for antigen, and they attack the microbes with the same basic vigor no matter how many times they have seen the same pathogen. Act fast: immediately within minutes – hours after infection. The encounter with the target leaves NO MEMORY → the response is not enhanced by repeated exposure. Several Lines of Protection Mechanisms Innate Immune Components/Barriers They include physical (anatomic) barriers, physiologic barriers, Biological, innate cellular response, and inflammation. Physical (anatomic) barriers: The skin: most pathogens can’t invade intact skin. The pH of the skin is also slightly acidic and can retard the growth of pathogenic organisms. The respiratory tract: is lined with cilia that physically attempt to remove microbes as they enter. Saliva and mucous are also difficult environments for microbes to live in, as there are many antimicrobial enzymes and chemicals within those entities. The GI tract is also a mucous membrane with similar properties to the respiratory tract; however, pathogens that enter here must first survive a trip through the stomach with a highly acidic pH that kills many microorganisms. Sticky mucus on mucus membranes entraps any foreign material. Skin & Mucus Membranes Physiologic Barriers:.Temperature: – Many microbial pathogens can’t survive much past human body temperature..pH: – The acidic pH of the stomach impedes the growth and transmission to the gut of many pathogens. – The skin is also acidic and retards the growth of many microorganisms..Chemical: – Lysozyme present in secretions such as tears, saliva, breast milk and mucous can break down the cell wall peptidoglycan of bacteria. – Defensins found within phagocytes can form pores in bacteria and fungi..Interferons: – IFN-α and IFN-β are anti-viral interferons. Innate immunity mechanisms Chemical Components lysozyme: Destroys peptidoglycan of the bacterial cell wall → lysis. Blinking, sneezing, coughing reflexes expel foreign particles. The flushing action of saliva, tears and urine helps in washing microbes from the body. Sweat, sebaceous secretions contain substances that inhibit microorganisms. Normal Bacterial Flora compete with pathogens for attachment sites and for essential nutrients. Some also: Produce bacteriocins and acids that destroy pathogenic microorganisms = A biological barrier External defenses: BARRIERS What happens when the physical and physiological barriers are breached? Damage to surface barriers e.g. by cuts, needle sticks, wounds, smoking or exposure to air pollutants, alcohols, narcotics, etc. can suppress this line of defense and allow entry of foreign organisms into internal tissues → infection. Innate Cellular Response: Phagocytic cells (monocytes/macrophages, neutrophils and dendritic cells) are part of the fist line of defense against invading pathogens. They recognize pathogens via shared molecules that are not expressed on host cells. Receptors of the innate immune system are referred to as pattern recognition receptors (PRRs). PRRs recognize pathogen-associated molecular patterns (PAMPs), molecules that are shared by pathogens of the same type (e.g bacterial LPS). These receptors are present intrinsically, encoded in the germline genes, and are not generated through somatic recombination as the lymphocyte receptors are generated. The innate immune system can recognize
