The Immune system Macrophages are just one of the defenses our bodies use against infection ex a microphage engulfing a yeast cell These defenses are collectively called the IMMUNE SYSTEM TWO general categories of Immune mechanisms are Innate immunity and Acquired immu nity Innate Immunity Recognition of traits shared by broad ranges of pathogens using a small set of receptors rapid response Defense mechanisms we are born with Do not require prior exposure to pathogen Work against general groups of pathogens Innate immunity s barrier defenses include the skin mucous membranes and secretions Skin Tough waterproof protection Secretions from sweat glands are acidic and toxic Mucous and secretions Mucous is secreted in nasal passages and the trachea trap mi crobes which are then swept upward and out of body by CILIA Saliva tears and other mucous secretions continually clean and bath the outsides of our to fungi body Innate immunity s internal defenses include Phagocytic cells Antimicrobial proteins Inflam matory response natural killer cells 1 Phagocytic white blood cells recognize and destroy sets of pathogens by recognizing molecules on the surface of these pathogens Receptors on white blood cells called toll like receptor TLR Toll like receptors Gives white blood cells the innate ability to recognize foreign invaders Invaders are trapped into the internal vesicle fuses with lysosome that has enzymes to de grade and destroy invaders TLR4 lipopolysaccharides on bacterial cells TLR3 Double stranded RNA genome in certain viruses TLR5 Flagellin in bacteria and other microorganisms NEUTROPHILS the most common type of white blood cells comprising about 50 70 of all white blood cells survive the act known as chemotaxis They are phagocytic meaning that they can ingest other cells though they do not Neutrophils are the first immune cells to arrive at a site of infection through a process Though neutrophils are short lived with a half life of 4 10 hours when not activated and immediate death upon ingesting a pathogen they are plentiful and responsi ble for the bulk of an immune response They are the main component of pus and responsible for its whitish color Neutrophils are present in the bloodstream until signaled to a site of infection by chemical cues in the body MACROPHAGES from monocytes are white blood cells within tissues produced by the differentiation of monocytes Human macrophages are about 21 micrometres 0 00083 in in diameter Monocytes and macrophages are phagocytes acting in both non specific defense innate immunity as well as to help initiate specific defense mechanisms adaptive immu nity of vertebrate animals Their role is to phagocytose engulf and then digest cellular debris and pathogens ei ther as stationary or as mobile cells and to stimulate lymphocytes and other im mune cells to respond to the pathogen EOSINOPHILS are white blood cells that are one of the immune system components re sponsible for combating multicellular parasites and certain infections in vertebrates Along with mast cells they also control mechanisms associated with allergy and asthma They are granulocytes that develop during haematopoiesis in the bone marrow before migrating into blood are eosinophilic or acid loving In normal individuals eosinophils make up about 1 6 of white blood cells and are about 12 17 micrometers in size They are found in the medulla and the junction between the cortex and medulla of the thymus and in the lower gastrointestinal tract ovary uterus spleen and lymph nodes 2 Antimicrobial peptides and proteins Peptides recognize groups of pathogens insert into membrane and disrupt membrane and destroys the cell Interferons secreted by cells infected with virus and induce nearby cells to express sub stances that inhibit viral growth Inhibit spread of infection Complement a group of about 30 proteins are always present in blood in inactive state Activated by interaction with foreign microbes they trigger a series of reactions that destroys the invader 3 Inflammatory response a group of responses to tissue damage from a cut or infec tion blood vessels to dilate Macrophages and mass cells release signals including histamine which cause nearby Increased blood flow gives site of injury its red and inflamed appearance Fluid which is leaking from enlarged vessels causes swelling The overall result is increased delivery of phagocytes and antimicrobial peptides in blood to help fight infection and help wound heal System wide Reponses include increased production of white blood cells and fever Excessive system response leads to septic shock This creates High fever low blood pressure and is often fatal 4 Natural killer cells White blood cells from lymphocytes that recognize and destroy virus infected cells Class I MHC molecules are expressed by most of the cells in our body and the MHC mole cule is displayed on the surface of those cells MHC Major Histocompatibility com plex Killer cells recognize cells with MHC class I molecules and leaves them alone Cells infected with a virus usually stop expressing their MHC class I protein These cells are recognized by the killer cells which then secrete Perforin and Granzyme Perforin pokes holes in membrane of cells Granzyme enters cells and induces apoptosis death by suicide Immunity Acquired of receptors slower response recognition of traits specific to particular pathogens using a vast array Defense against specific Pathogens or toxins The full development of these mechanisms requires prior exposure to the pathogen or toxin A learned response Acquired Immunity s Humoral response include Antibodies that defend against in body fluids Acquired immunity s Cell mediated response includes cytotoxic lymphocytes that defend against infection in body cells Both INNATE AND ACQUIRED defenses are fighting against infection pathogens like microorganisms viruses
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