The Immune System Flashcards
What is non-specific response?
-Innate immunity/born with it
-Aiming to stop any pathogens getting in, regardless of what they are
-Includes: physical, chemical, mechanical barriers
What is inflammation?
-Second line of defence
-Its where white blood cells (e.g. macrophages and neutrophils) are drawn to the infected the area
What does inflammation do?
-Stops/reduces bacteria growth
-Initiates tissue repair
-Involves: fever, heat, sweating
What does a fever do?
-Hypothalamus raises body temperature to inhibit bacterial growth
-Specific immune responses work better at higher temperatures
How does inflammation work?
-Mast cells and basophils release chemicals called histamines
-The histamines cause blood vessels to dilate causing heat and redness
-Pathogen finds it harder to reproduce
What is a primary defence?
Physical and chemical barriers
-Physical = skin, hair, mucus
-Chemical = acid, lysozymes
What is specific response?
A specific response to specific pathogens
-Each T cell and B cell are tailored towards a specific pathogen, not effective against others
What are the key features of a specific immune response?
-Distinguish self from non-self
-Specific to each foreign cell
-Diverse so can recognise potentially any foreign antigen
-Immunological memory causes a rapid secondary response
What is a humoral response?
Body fluid
-Immune response to pathogens free in the tissues and bloodstream
-Involves specific antibodies
What is a cell mediated response?
Response to own body cells that have altered self-antigens
e.g. cells that have become infected by a virus or cells that have become cancerous
What is MHC?
Major Histocompatibility Response
-A molecule found on the cell surface membrane of all cells and is used to present antigens
-Self and non-self antigens
What are the steps for phagocytosis?
-Phagocytes engulf pathogens (e.g. neutrophils and macrophages)
-Pathogens are engulfed into a phagocyte
-Phagocyte is fused with a lysosome to form a phagolysome
-Lysozymes in the lysosome digest the pathogen
-Cytokines are released from the phagocytes to stimulate other phagocytes in the area
-Presents an antigen on the MHC
What is a phagocytic cell?
Antigen presenting cells
-After they engulf the pathogen they will present antigens or pathogens on their surface attached to the MHC molecule
What is a T helper cell?
-Made in the bone marrow
-Mature in the thymus gland
-They each have a T cell receptor on its surface that fits a specific antigen
-They can only recognise the antigen presented to them on MHC from an antigen presenting cell
What do T helper cells do?
-Divide rapidly by mitosis, creating many clones
-Develop memory cells, stimulate phagocytes, stimulate B cells
-Some T cells remain in the blood as lymph and memory T cells which are ready to recognise the same antigen again
What is a B cell?
Made and matured in the bone marrow
What do antibodies do?
-Opsonins = bind to an antigen and make the pathogens so that phagocytes can recognise foreign cells
-Agglutinins = bind to the antigens causing pathogens to clump together to prevent the pathogens from reproducing
-Lysins = bind to antigens causing pathogens to rupture
What is B cell activation?
-Must become activated
-Might only have one copy of the right B cell that has complimentary antibodies to a pathogen antigen
What is activation without T cells (independent activation)?
-B cell and membrane bound antibodies recognise and attach to antigens
-B cell becomes activated, divides by mitosis and produces antibodies
What is activation with T cells (dependant activation)?
-B cell antibody receptor matches with complimentary antigen B cell
-Internalises with the antigen and presents it on its surface
-Activated T cells bind to the B cell by the presented antigen
-The T cell produces cytokines which activate the B cell
-The B cell divides by mitosis to produce memory B cells and B effector cells
-These eventually differentiate into antibody producing plasma cells
What is T killer cell activation?
-Antigen presenting cell digests and engulfs pathogen and presents it on its surface via MHC
-T killer cell is complimentary with antigen on the antigen presenting cell
-Assistance of cytokines from an activated T helper cell, the killer T cell becomes activated
-Active killer T cells and T killer memory cells are formed
-Active T killer cells release perforins chemicals, these punch holes in the membrane of infected cells and cause them to burst
What is a killer T cell (cytotoxic CD8+)?
-Attack body cells which have been anti-genetically altered by viruses or cancer cells
-They destroy the pathogen by punching holes through their cell surface membranes so the cell contents spill out (cell lysis)
What is an antigen presenting cell?
-Engulf and digest pathogens and will present parts of the pathogen on their surface attached to the MHC molecules
-Macrophages engulf and digest pathogens and present them on their surface
-Antigens are presented to T cells and their T cell receptors which activates those cells
-Activated T cells divide by mitosis creating many more identical copies of each specific T cells
What is artificial passive immunity?
When antibodies are introduced from outside the body, you don’t have to make them yourself
When is artificial passive immunity used?
-Can be used if there’s not a vaccine yet
-Immediate so don’t need to wait for antibodies to be made
-Short term so the person won’t have long lasting protection
What is natural passive immunity?
E.g. an infant receives a mothers antibodies through the placenta or breast milk
What is active immunity?
Involves exposure to a pathogen or antigen
-Either through natural exposure (natural active)
-Vaccination (artificial active)
How does active immunity work?
-Requires exposure to antigen (e.g. vaccine or infection)
-Body makes their own antigens
-Develops slowly
-Long term because memory cells enable faster antibody production or reinfection
How does passive immunity work?
-Doesn’t require exposure to antigen
-Body given antibodies made by someone else (e.g. infection, placenta, breast milk)
-Immediate
-Short term as antibodies are broken down and no memory cells are made
What is a vaccination?
-Aims to stimulate a primary immune response without actually causing the disease like a normal infection would
-Allows people to safely/normally develop memory cells against a pathogen
