Rachel Spells PET 3323 Exam 3 Study Guide The Immune System Immune System Overview It is a functional system made up of two intrinsic defense systems that act independently and cooperatively to provide resistance to disease Innate NONSPECIFIC Defense System o 1st and 2nd line of defense respond within minutes o 1st External membrane skin mucosa o 2nd Takes effect when 1st has been penetrated inflammation proteins phagocytes example cutting the skin o Immediate response time Adaptive SPECIFIC Defense System o 3rd line of defense o These consist of T and B lymphocytes they respond to a specific target Show adaptation over time set you up for immune responses throughout life o Attack foreign substances o This system takes longer than the innate to work KNOW that innate and adaptive systems are intertwined o Proteins released during an innate response alerts cells of the adaptive system about the presence of a foreign substance o The 1st and 2nd line of defense get the T and B cells ready to respond to them o Essentially the innate system sets the adaptive system up to be effective 1st Line of Defense Surface Barriers Skin mucous membranes and their secretions are the body s 1st line of defense Keratin keratinization hardening dead cells in the skin provides a tough barrier as the first line Mucous membranes provide the lining for all body cavities that open to the exterior o Serves as physical barriers o And also secrete protective chemicals Surface Barriers cont Skin keratinized epithelial membrane resistant to most weak acids and bases toxins Many layers of cell provide this 1st line of defense Mucous membranes secrete protective chemicals o Acidity of skin pH 3 5 inhibits bacterial growth o Stomach mucosa secretes HCl and protein digesting enzymes to kill microorganisms when you eat food o Saliva and lacrimal fluid contain lysozymes which destroy bacteria o Mucus traps microorganisms trying to enter these openings because it is sticky A little cut can enable and elicit internal innate system the 2nd line of defense is now activated 2nd Line of Defense Nonspecific Cellular and Chemical Defense 2nd line killing pathogens and repair tissue Phagocytes 2 types confront pathogens digest foreign substances 1 L of human blood has 6 million phagocytes they are while blood cells they are also in the lymph 1 Macrophages Leave the blood stream in search of foreign substance large eater It is the main phagocyte and if they recognize foreign substance they will undergo phagocytosis 2 Neutrophils Also a phagocyte but NOT phagocytic unless they encounter the targets almost like a secondary phagocyte They are the most abundant white blood cell o They are BOTH derived from white blood cells which originate from red bone marrow Natural Killer Cells NK cells they recognize foreign substance They check the ID and if the substance doesn t have one they kill it o They act like T lymphocytes BUT they are not specific to a pathogen Inflammatory response Cytokines are part of this type of response talked about later Antimicrobial Proteins complement proteins and interferons Fever Phagocytosis Destroy pathogens or clean up dead cells 1 Phagocyte adheres to pathogen or debris 2 Phagocyte forms pseudopods that eventually engulf the particles forming a phagosome 3 Lysosome fuses with the phagocytic vesicle forming a phagolysosome lysosome contain strong digesting enzymes 4 Lysosomal enzymes digest the particles leaving the residual body 5 Exocytosis of the vesicle removes and indigestible and residual material This mechanism lets the other cells know they are antigen presenting cells They present the pathogen to the T cells Essentially these connect the 2nd line and the 3rd line of defense Phagocytosis cont Adherence is made possible by recognizing the pathogen o Complementary proteins help with this inactive protein o Vaccine containing a weakened antigen or dead antigen initiates an immune response readiness of immune cells Methods of Pathogen Destruction KNOW ALL 4 o Simple digestion by Lysosomal enzymes o Respiratory burst free radicals which kill cells o K enters phagosome pH rises activates protein digesting enzymes that digest the invader Basically changes enzyme activity o Defensins are chemicals produced by neutrophils that pierce the pathogen membrane water will come into the cell and destroy the pathogen Natural Killer Cells NON phagocytic White blood cell found in both the blood and the lymph Defensive cells that can kill infected cells before the adaptive immune system is activated o Including cancer cells They eliminate cells through direct contact by o Determining the lack of cell surface receptors the ID of the cell the receptors on the cell membrane remember they are checking ID s They re like club bouncers o Determining certain cell surface sugars glycoproteins on the cell membrane Secrete chemicals that enhance the inflammatory response Stimulate apoptosis of target infected cell cell death a The activation receptor on the NK cell recognizes the glycoprotein carbohydrate complex on the cell membrane and a chemical is produced inside the NK At the same time the NK cell has the inhibitory receptor that detect MHC class I receptors The produced chemical will then NOT release the chemical Your body responds to your own cell by not killing it o Every one of your cells has MHC class I receptors b If the target cell does not have MHC class I there is no inhibition to stop the secretion of the chemical In this case it is cytokine causing apoptosis of the target cell The two chemicals that NK cells release 1 Peroforin cytokine protein creates a large pore in target cell 2 Granzyme cytokine protein enters cell and induces apoptosis Note T cells also follow this mechanism Innate to Internal Defenses Inflammatory response is triggered when body tissues are injured 1 Prevents the spread of damaging agents to nearby tissues 2 Disposes of cell debris and pathogens 3 Sets the stage for repair Four cardinal signs redness heat swelling and pain may hinder joint movement impairment of function Innate to Internal Defenses Upon injury SEE PIC ABOVE Release of chemical mediators such as cytokines promote inflammation and attract WBCs histamine by mast cells kinins prostaglandins leukotrienes and complement proteins will induce vasodilation of small blood vessels in the injured area o More blood flow hyperemia accounts for redness and heat o Prostaglandins are a byproduct of fatty acids important for
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