The Immune System

Question 1

What is non-specific response?

Answer 1

-Innate immunity/born with it
-Aiming to stop any pathogens getting in, regardless of what they are
-Includes: physical, chemical, mechanical barriers

Question 2

What is inflammation?

Answer 2

-Second line of defence
-Its where white blood cells (e.g. macrophages and neutrophils) are drawn to the infected the area

Question 3

What does inflammation do?

Answer 3

-Stops/reduces bacteria growth
-Initiates tissue repair
-Involves: fever, heat, sweating

Question 4

What does a fever do?

Answer 4

-Hypothalamus raises body temperature to inhibit bacterial growth
-Specific immune responses work better at higher temperatures

Question 5

How does inflammation work?

Answer 5

-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

Question 6

What is a primary defence?

Answer 6

Physical and chemical barriers
-Physical = skin, hair, mucus
-Chemical = acid, lysozymes

Question 7

What is specific response?

Answer 7

A specific response to specific pathogens
-Each T cell and B cell are tailored towards a specific pathogen, not effective against others

Question 8

What are the key features of a specific immune response?

Answer 8

-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

Question 9

What is a humoral response?

Answer 9

Body fluid
-Immune response to pathogens free in the tissues and bloodstream
-Involves specific antibodies

Question 10

What is a cell mediated response?

Answer 10

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

Question 11

What is MHC?

Answer 11

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

Question 12

What are the steps for phagocytosis?

Answer 12

-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

Question 13

What is a phagocytic cell?

Answer 13

Antigen presenting cells
-After they engulf the pathogen they will present antigens or pathogens on their surface attached to the MHC molecule

Question 14

What is a T helper cell?

Answer 14

-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

Question 15

What do T helper cells do?

Answer 15

-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

Question 16

What is a B cell?

Answer 16

Made and matured in the bone marrow

Question 17

What do antibodies do?

Answer 17

-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

Question 18

What is B cell activation?

Answer 18

-Must become activated
-Might only have one copy of the right B cell that has complimentary antibodies to a pathogen antigen

Question 19

What is activation without T cells (independent activation)?

Answer 19

-B cell and membrane bound antibodies recognise and attach to antigens
-B cell becomes activated, divides by mitosis and produces antibodies

Question 20

What is activation with T cells (dependant activation)?

Answer 20

-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

Question 21

What is T killer cell activation?

Answer 21

-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

Question 22

What is a killer T cell (cytotoxic CD8+)?

Answer 22

-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)

Question 23

What is an antigen presenting cell?

Answer 23

-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

Question 24

What is artificial passive immunity?

Answer 24

When antibodies are introduced from outside the body, you don’t have to make them yourself

Question 25

When is artificial passive immunity used?

Answer 25

-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

Question 26

What is natural passive immunity?

Answer 26

E.g. an infant receives a mothers antibodies through the placenta or breast milk

Question 27

What is active immunity?

Answer 27

Involves exposure to a pathogen or antigen
-Either through natural exposure (natural active)
-Vaccination (artificial active)

Question 28

How does active immunity work?

Answer 28

-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

Question 29

How does passive immunity work?

Answer 29

-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

Question 30

What is a vaccination?

Answer 30

-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