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Responding to Antigens, Immunity - Coggle Diagram

- - - - Macrophages
        
        phagocytose foreign antigens and anyhting attached to the antigen
        
        releases cytokines to call other phagocytes and immune cells to area of infection
        
        antigen presenting
        
        derived from monocytes immature precursor resides in the bloodstream and then moves to tissue to mature
        
        recognises PAMPs
        
        long-lived compared to other phagocytes such as neutrophils
        
        consumes larger pathogens
      - Neutrophils
        
        typically the first respondents to invading foreign antigens
        
        phagocytose anything with the attached to the foreign antigen and will die after doing so once. Pus is composed of dead neutrophils and cell parts
        
        short lived and reside in the bloodstream
      - Mast Cells
        
        release histamine when exposed to foreign antigen
        
        most tissues characteristically surrounding blood vessels and nerves, and are especially prominent near the boundaries between the outside world and the internal milieu, such as the skin, mucosa of the lungs, and digestive tract, as well as the mouth, conjunctiva, and nose.
        
        allergic reactions
      - Dendritic Cells
        
        professional antigen presenting
        
        resides in tissue
        
        constantly sample extracellular fluid for foreign antigens
        
        has grooves to icnrease surface area and allows for it to sample more at once
        
        will present foreign antigen fragments on MHC I markers for T cells
        
        releases cytokines
        
        once activated will start to migrate towards lymph nodes, area with high concentration of adaptive immune cells
        
        consumes smaller pathogens
      - Basophils
        
        release histamine which contribute to the inflammatory response
      - Eosinophils
        
        antigen presenting
        
        release cytokines and cytotoxic chemicals
      - Natural Killer Cells
        
        a bridge between innate and adaptive immune systems
        
        can kill virus infected and cancerous cells (self)
        
        kills by releasing death ligands or by releasing peforin and granzymes
        
        can detect levels of MHC I and MHC II markers to identify if the cell is infected or cancerous
        
        releases cytokines and attaches to the potentially virus infected or cancerous cell for other immune cells
      - Monocytes
        
        WBCs
        
        phagocytosis
    - - around 30 proteins that circulate the blood plasma
      - assist phagocytes in recognising pathogens
      - activated when exposed to foreign antigens
      - attract phagocytes to area of infection
      - lyse cell membrane to further simulate phagocytic action by punching a hole into the membrane
      - attach to foreign antigens making the pathogen easily identifiable for other immune cells
      - contribute to inflammation by increasing permeability of capillaries and attracting phagocytes to area of infection
    - - Interferons
        
        a type of cytokine
        
        increases antiviral defences in cells neighbouring the infected cell
        
        can attract NK cells
        
        produces enzymes that breakdown viral RNA
        
        limits the transcription of viral RNA and therefore replication
        
        stimulate increased production of MHC I markers to attract the attention of adaptive immune cells
        
        upregulation of cytokines
      - Chemokines
        
        a type of cytokine
        
        acts as chemical attractants
        
        attract leukocytes to area of infection
    - - Process
        
        Toll-like receptors (TLRs) on a phagocyte interact with a microbe’s pathogen-associated molecular patterns (PAMPs) causing signal transduction events to occur.
        
        Leads to the activation of the phagocyte.
        
        The activated phagocyte engulfs the microbe, with the plasma membrane forming a vacuole called a phagosome around it.
        
        A lysosome containing digestive enzymes fuses with the phagosome, forming a phagolysosome, which breaks down the foreign material.
        
        The fragments can then be expelled from the cell by exocytosis.
    - - nonspecific resistance that destroys invaders in a generalized way without targeting specific individuals
  - - - intact skin, hair, cilia, mucous membrane, kerotonised skin,
    - - stomach acid, lysozymes, tears
    - - microflora, good bacteria
- - - - B lymphocytes
        
        B plasma cells
        
        factories specialising in antibody production
        
        produces thousands of antibodies per second
        
        contains a lot of rough endoplasmic reticulum to assist in antibody production
        
        specifically directed against invading bacteria and viruses and their toxins (extracellular)
        
        B memory cells
        
        remain in the lymphoid tissue for extended period of time maybe even up to a lifetime
        
        responsible for immunity for future exposure to the reappearing antigen
        
        can divide and give rise to B plasma cells upon subsequent exposure
        
        T helper cells helps activate B memory cells upon subsequent infection to fight off the pathogen by producing a faster and bigger immune response
        
        Clonal Selection Theory (also happens for T cells)
        
        idea that immature lymphocytes in the body that once activated by an antigen will start to clone similar cells
        
        B lymphocytes once activated by complementary specific antigen will become metabolically activated undergo clonal selection and proliferate
        
        requires T helper cells
        
        selection of a naive B lymphocyte that has a complementary antibody for the invading antigen
        
        Clonal Expansion (also happens for T cells)
        
        once clonal selection has happened the selcted B lymphocyte will undergo clonal expansion
        
        B lymphocyte will proliferate and give rise to to two different daughter cells B plasma cells and B memory cells that are equipped with the required antibody
        
        Originates in the bone marrow from stem cells
        
        Matures in peripheral lymphoid organs and tissue e.g. spleen
        
        small, non-dividing and relatively inactive cells
        
        has attached antibodies that are specific so one B cell can only bind to one particular type of antigen
        
        Activated when B cell comes into contact with its complementary antigen, binds to the antigen with the assistance of T helper cells
      - Antibodies
        
        large globular glycoproteins
        
        bind to specific antigen molecules
        
        released into blood and lymph
        
        highly selective
        
        y shaped, light and heavy chain variable and constant regions
        
        variable region cutting and shuffling of genes to produce different antigen binding site shapes
        
        may act in singly, dimer, pentamers
        
        immunoglobulins
        
        Types in mammals
        
        IgeE (allergic reactions)
        
        IgG (secondary response)
        
        IgM (primary response)
        
        IgA
        
        IgD
        
        bound by disulfide bridges
        
        Antigen-Antibody complex
        
        does not directly destroy pathogen
        
        interferes with the function of the pathogen
        
        immobilise pathogen
        
        allow phagocytes to easily engulf pathogen
        
        inactive pathogens
        
        attract complement
        
        agglutinate pathogens
        
        prevent reproduction of pathogens
        
        flag other immune cells such as phagocytes
        
        Processes
        
        agglutination
        
        clump and phagocytosis
        
        Neutralisation
        
        encapsulate
        
        Precipitation
        
        antibodies binds to soluble antigens making them insoluble and precipitate out of the solution
      - Complement System
    - - T lymphocytes
        
        mature in the thymus and originate in the bone marrow from stem cells
        
        have T cell receptors on surface
        
        T helper cells
        
        commanders of the immune system
        
        located in the lymph nodes
        
        when phagocyte consume an invader it travels to the nearest lymph node to present the invader to T helper cells
        
        T helper cell is activated by an APC and once it recognises the presented antigen the Th cell will produce and secrete cytokines to activate B, T and other immune cells
        
        Th cell then locates a B cell that can produce specific antibodies against the specific antigen
        
        do not directly kill pathogens
        
        have specialised receptors
        
        produce and secrete cytokines
        
        T suppressor cells
        
        regulate immune response and stop activity when the invader has been defeated
        
        prevent wastage of resources and energy
        
        T cytotoxic cells
        
        effector cells of the cell-mediated response
        
        recognise and kill foreign, infected or abnormal cells including virus-infected host cells, cancer cells, foreign tissue from transplant
        
        release perforin and granzymes
        
        granzymes initiate the process of apoptosis
        
        activated by foreign antigens and cytokine secreted from the Th cells
        
        only eukaryotic pathogens not much for prokaryotic pathogens
        
        Memory T cells
        
        produced after the activation of Th and T cytotoxic cells
        
        Th and T cytotoxic differentiate into memory T lymphocyte that are antigen specific
        
        persist after infection is resolved to ensure a prompt response should the same pathogen reinfect the organism
      - mediated by T cell receptors
        
        made of two polypeptide chains
        
        heavy and light chains and has only one antigen binding site
        
        does not bind to antigens on pathogen instead bind antigen fragments presented by APCs
        
        Receptor binding triggers signal transduction in the T lymphocyte.
        Resulting in proliferation, cytokine release and activation of cytotoxic function.
      - steps of cell-mediated
        
        T lymphocytes differentiate between self and non-self cells, inability of T cells to respond to self cells is known as self tolerance
        
        TCRs on the Helper T lymphocytes recognise the antigen-MHC-II complex.
        
        Signal transduction in T helper lymphocyte leads to activation of the cell, which then proliferate and releases cytokines.
        
        Cytokines activate cytotoxic T lymphocytes.
        
        Antigens are presented to cytotoxic T lymphocytes by major histocompatibility complex 1 (MHC-1) molecules.
        
        Cytotoxic T cells release perforins which destroy infected cells.
    - - Ability to recognise and respond exclusively to specific antigens.
      - Cells of the adaptive immune system trigger an array of defensive mechanisms that destroy the pathogen.
    - - The ability of the immune cells to ‘remember’ antigens after primary exposure.
      - Mount a larger and more rapid response when exposed to the same antigen again.
    - - Primary Response
        
        response that arises from the first encounter of B or T lymphocyte with antigen
        
        B and T lymphocyte form B and T memory cells
        
        IgM antibodies are the predominant antibodies produced during this response
      - Secondary Response
        
        response that arises from subsequent exposure to the same antigen
        
        lymphocyte proliferation and production of antibodies occur much faster
        
        IgG antibodies are predominant antibodies produced during this response
        
        larger and more efficient repsonse to the same antigen due to the presence of B and T memory cells