(2) cells: cell recognition and the immune system Flashcards
what are the 2 types of immune system response?
non specfic: inflammation, phagocytosis, interferons, lysozymes
specific: T-cells, B-cells (antibodies)
what is a lysozyme?
an enzyme that disrupts the cell walls gram-positive bacteria by digesting the peptidoglycan
found in human tears, saliva and lysosomes
what are interferons?
proteins produced by virus-infected body cells in response to the vrius
trigger the production of a second protein that inhibits viral replication by binding to mRNA coded by the virus
how does inflammation work as a localised response?
- tissue = damaged and pathogens may enter body, damaged cells will release chemical substances (histamines) which acts as inflammatory mediators
- chemicals cause an increase in blood and permeability of the capillary, area becomes flooded with fluid and blood-clotting elements causing swelling n redness
- tissue cells also release chemicals (e.g chemokines) that attract phagocytic white blood cells such s as neutrophils and macrophages
- phagocytosis begins when macropjages recognise invading bacteria as pathogens
- cell membrane of the macrophages fuses around a single bacterium, trapping it inside a phagosome
- the phagosome fuses with a lysosome to form a phagolysosome and the bacterium is broken down and killed
- when the bacterium is destroyed, the macrophage absorbs any useful material and expels the rest through exocytosis
- as pathogens are destroyed, anti-inflammatory factors begin to work so inflammation doesn’t continue longer than is necessary
swelling will reduce and skin will eventually heal
how is a phagolysosome formed?
- phagocytic cell is attracted to pathogen by chemical trail
- receptors on phagocyte attach to antigens on pathogen
- membrane infolds and lysosomes migrate towards the phagosome
- lysosomes fuse w phagosome to form phagolysosome
- pathogen digested by lytic enzymes
what are the characteristics of specific immune response and what are the main 2 types?
it can target a specific pathogen
slower to act than the non-specific response
cell mediated response
humoral / antibody mediated response
what are lymphocytes?
white blood cell found in the blood and lymph nodes
produced by stem cells in bone marrow
2 types: T cell, B cell
what is the role of helper T cells?
acts as a ‘co-ordinator’ of the immune response
when a pathogen is detected, helper T cells produce a chemical signal resulting in the proliferation of specific cytotxic T cells and effector B cells
activates B cells and helps produce memory cells
what is the role of cytotoxic T cells?
recognises infected cells/tumour cells
destroys them by secreting proteins that rupture their membranes, causing the cell to lyse
what is the role of effector B cells?
- multiply and give rise to plasma cells when activated by helper T cells
may become memory B cells
what is the role of plasma cells?
develop from effector B cells
produce large amounts of antibodies, which bind to a pathogen and cause it to be destroyed or inactivated
what is the role of memory cells?
circulate in the blood after the pathogen has been removed
if stimulated, they divide and rapidly produce a secondary immune response
what happens during the cellular mediated response?
- when a macrophage destroys a pathogen by pathogen by phagocytosis, it will display a pathogens antigen on its cell surface: becomes an antigen presenting cell
- APC interacts w specific helper T cell and releases a chemical substance called interleukin 1 ( cytokine [chemical involved in cell signalling])
- interleukin 1 stimulates helper T cell to release another cytokine (interleukin 2) which stimulates the growth and development of antigen specific cytotoxic T cells
- Cytotoxic T cell detect the antigen on the surface of the infected body cells and produce perforin; it forms pores in te target cell’s membrane, allowing ions and water in and causing the lysis of the cell
- exposure to a specific antigen results in memory T cells being produced, ready to initiate a response to the same pathogen if the body becomes infected again in the future
what happens during a humoral immune response?
- when a macrophage destroys a pathogen by pathogen by phagocytosis, it will display a pathogens antigen on its cell surface: becomes an antigen presenting cell
- APC interacts w specific helper T cell and releases a chemical substance called interleukin 1 ( cytokine [chemical involved in cell signalling])
- interleukin 1 stimulates helper T cell to release another cytokine (interleukin 2) which stimulates the differentiation of effector B cells into plasma cells
- the plasma cells divide and produce large quantities of antigen-specific antibodies: these attach to the pathogen and destroy it by neutralisation/agglutination
- exposure to a specific antigen results in memory B cells being produced, ready to initiate a response to the same pathogen if the body becomes infected again in the future
what are the components of an antibody?
antigen binding site
disulphide bonds
polypeptide chains
constant regions
variable regions