The Immune System - All notes Flashcards
What is immunity?
-The ability to resist damage from pathogens, toxins and internal threats
What makes up the immune system?
-Lymphoid tissue, immune cells and chemicals that co ordinate and carry out immune functions
What are the functions of the immune system?
-Recognise and remove abnormal ‘self’ cells, removes dead or damaged cells, protects from disease-causing invaders
What are the types of immune response ?
-Non-specific innate immunity and specific acquired immunity
What is the lymphatic system?
-System of vessels, cells and organs carrier excess fluids to the bloodstream and filters pathogens from the blood
What is the lymph ?
-Interstitial fluid once it has entered lymphatic vessels
What are the functions of the lymphatic system?
-Fluid balance, lipid absorption and defence against pathogens
What is a pathogen ?
-A substance or microorganism that causes disease or damage to the tissues of the body
What organs contribute to drainage?/
-Tonsils, lymph nodes, spleen, and thymus
What are lymph nodes?
-Located along lymphatic vessels where lymph passes through before going into the blood; stimulates lymphocytes to divide and removes pathogens using macrophages
What does a lymph do?
-Carries fluid from tissues to circulatory system, forced through vessels by contraction of skeletal muscles
What are the functions of capillaries in the lymphatic system?
-Where fluid enters the lymphatic system, have thinner walls to allow movement and has overlapping epithelial flaps so fluid only moves into capillaries
What is chyle?
-Milky fluid that drains from the intestinal lacteals containing lipids and lipid soluble proteins and vitamins
What are the lymphatic capillaries found in the small intestine?
-Lacteals
How does lymphatic system circulate ?
-Lymphatic capillaries to vessels to trunks to the 2 ducts
How does the right lymphatic system drain?
-The right side of the head, throat and right arm drain from the right lymphatic duct and drains into the right subclavian vein
How does the left lymphatic system drain?
-The rest of the body drains from the thoracic duct drains into the left subclavian vein
What are tonsils?
-Protective ring of lymphatic tissue around the nasal and oral cavities and the pharynx protect from food pathogens
What are the functions of the spleen?
-Filters the blood, responds to foreign substances and destroy old RBC
What types of tissue make up the spleen?
-White pulp and red pulp
What is white pulp?
-Lymphatic tissue around the arteries in the spleen where lymphocytes can be stimulated to divide
What is red pulp?
-Surrounds the veins and contains macrophages and red blood cells
What is the thymus?
-A two lobed gland divided into lobules where mature T cells migrate to the medulla, enter the blood and travel to other lymphatic tissue
What are the cells of the immune system?
-Leukocytes, eosinophils, basophils, neutrophils, monocytes and macrophages, lymphocytes and plasma cells, dendric cells
What are basophils and mast cells?
-Release mediators that contribute to inflammation eg. heparin and histamine. Basophils in circulation and mast cells in tissues
What are eosinophils ?
-Respond to allergic reactions and parasitic diseases in the digestive tract, lungs, urinary, and genital epithelia. They are cytotoxic
What are neutrophils ?
-Phagocytic WBC with a segmented nucleus that kill and ingest bacteria
What are monocytes and macrophages?
-Monocytes are precursors of macrophages, once in the tissues monocytes enlarge and differentiate into phagocytic macrophages
What are APCs?
-Antigen presenting cells that can insert fragments of processed antigen into its membrane to become part of the surface protein complex
What are the 3 sub types of lymphocytes ?
-B lymphocytes, T lymphocytes and natural killer cells
What are dendritic cells?
-Antigen presenting cells found in the skin that capture antigens and migrate to lymph nodes
What is specificity?
-Where adaptive immunity recognising a particular substance eg. specific virus
What are the features of innate immunity?
-Rapid and non-specific, consists of physical barriers, chemical mediators, leukocytes, inflammatory response to enhance adaptive immune response
What are the physical barrier?
-Skin, mouth, stomach, mucosal epithelia, tears, saliva and urine
What are the types of chemical mediators ?
-Complement and cytokines
What are types of cytokines?
-Interleukins, interferons, chemokine
What are the features of complement chemical mediators ?
-Are proteins within plasma, normally inactivated but once activated a series of reactions occurs
Explain the reaction series after a complement chemical mediator has been activated ?
-Binds to cell membrane of pathogen labelling it for phagocytosis, act as chemotactic agents to attract phagocytes to site of inflammation, form damaging pores in the plasma membrane (membrane attack membrane)
What are cytokines ?
-Small signalling molecules released from cells to trigger immune response
What is adaptive immunity?
-Response to pathogens improves with each encounter, is specific and can memorise
What do chemical mediators do?
-Promote the immune response
What do interferons do?
-Are secreted by cells infected by a virus to travel to adjacent cells and induce them to make antiviral proteins to inhibit viral reproduction, can also activate other immune cells
What are the features of white blood cells?
-Produced in red bone marrow, many different types
How do neutrophils and macrophages work together?
-After a neutrophil has died after signalling for an immune response the macrophage will clean it up along with other cell debris
What are the types of white blood cells?
-Basophil
-Eosihophil
-Lympocyte
-Neutrophil
-Monocyte
What do natural killer cells do?
-Recognise the type of cell eg. tumour or virus and kill their target cell by damaging cell membrane to allow extracellular fluid into the cell
Explain how the inflammatory response is initiated ?
-Tissue injury causes mast cells or basophils to degranulate
What happens when basophils degranulate in the inflammatory response?
-Release of chemical mediators, vasodilation (histamine and prostaglandin), increased vascular permeability (histamine), recruitment of phagocytes
What are the features of lymphocytes ?
-Each clone is from a single B or T cell, respond only to a particular antigen, becomes activated when receptor combines with antigen and multiplies
What are MHC class II molecules?
-APC-macrophages, dentritic, lymphocytes
What is the MHC-antigen complex?
-Helps that antigen to present to another lymphocyte
What is an MHC class I molecule?
-A non-antigen presenting MHC
How do helper T cells proliferate?
-MHC class II molecules needs a complementary T cell, secreted cytokines and CD molecules (help them bind) to be stimulated to divide and help B cells and other T cells to be activated
How do T helper cells help B cells become activated?
-Takes in same antigen as helper T cell, gets presented on surface of the B cells by MHC class II molecule, T cell binds to MHC II / antigen complex using CD4 to stimulate B cell to divide
What do B cells divide into?
-Plasma cells and antibodies
What are the features of antibodies ?
-Bind to extracellular antigens y- shaped protein of 4 polypeptide chains (2 heavy 2 light) variable region (binding site) and constant region
What is the primary response in antibody production ?
-Exposure to antigen, B cell divides, forms plasma and memory B cells, plasma cells produce antibodies, normally develops disease symptoms, after antigen destroyed antibodies degrade and plasma cells die
What is the secondary response in antibody production?
-If previously exposed to antigen, memory B cells quickly divide to form plasma cells, makes more memory cells, quicker to produce antibodies, more plasma cells and antibodies
What are IgG antibodies ?
-Secondary immune response, some can cross the placental membrane
What are IgA antibodies?
-External secretions eg. saliva, tears, mucus
What do IgE antibodies do?
-Targets gut parasites and are associated with allergic responses
What do IgM antibodies do?
-Primary immune response
What are the features of cytotoxic T cells?
-Intracellular effects, essential in viral infections and antibodies can’t enter cell, destroys infected cell
How are cytotoxic T cells proliferated ?
-Virus infects cell, some viral proteins become processed antigens, combine with MHC class I molecules, T cell receptor binds with MHC-antigen complex with the help of CD8, and other helper cells which stimulates the T cell to divide
What does a cytotoxic T cell divide into?
-Additional cytotoxic T cells and memory T cells
What are two functions of cytotoxic T cells?
-Release cytokines, attract other immune cells, active additional cytotoxic T cells directly kill virus infected cells-cause them to lyse
What is an allergic response?
-An immune response to a non-pathogenic antigen that is not typically harmful to the body
How does an allergic response occur?
-Allergen processed by antigen presenting cell which then activated helper T cells. This then binds to B lymphocytes which the differentiates into plasma cells which secrete antibodies. Mast cells with these antibodies are then re exposed to the allergen and degranulate releasing cytokines and histamine causing inflammation and the allergic response
