Immunity Flashcards
What is the other name for antibodies?
immunoglobulins
Antibody structure
Y shaped glycoproteins
- two identical polypeptide chains called ‘the heavy chains’
- two shorter ‘light chains’
- chains held together by disulphide bridges
variable region
binding site of about 110 amino acids on the heavy and light chains.
Specific as different on every antibody
contstant region
bit of an antibody that doesn’t change ie. not the variable region (binding site)
opsonin
chemicals that bind to pathogens and tag them so they can be more easily recognised by phagocytes
- antigen-antibody complex acts as opsonin
agglutinins
antibodies act as agglutinins, causing pathogens with attached antigen-antibody complexes to clump together
-> helps prevent pathogens spreading throughout the body and makes it easier for phagocytes to engulf a number of pathogens at one time
anti-toxins
antibodies act as anti-toxins, binding to the toxins made by pathogens and making them harmless
b lymphocytes mature in the
bone marrow
t lymphocytes mature in the
thymus gland
what are the 4 types of T lymphocyte?
T helper cells
T killer cells
T regulator cells
T memory cells
what are the 3 types of B lymphocyte?
Plasma cells
B effector cells
B memory cells
interleukins
produced by T helper cells.
- type of cytokine (cell signalling molecule)
- stimulate the activity of the B cells, which
=== increase antibody production
=== stimulate the production of other types of T cells
=== attract and stimulate macrophages to ingest pathogens with antigen-antibody complexes
perforin
produced by T killer cells
- kills pathogen by making holes in the cell membrane so that it is freely permeable
T killer cells
destroy pathogen carrying antigen
- produce a chemical called perforin, which kills pathogen by making holes in the cell membrane so that it is freely permeable
T helper cells
- have CD4 receptors on their csm which bind to surface antigens on APCs.
- produce interleukins, which stimulate the activity of the B cells
T memory cells
live for long time
- part of immunological memory
- if they meet the same antigen again, they rapidly divide and form clones of T killer cells that destroy the pathogen
T regulator cells
- supress the immune system
- stop the immune response once a pathogen has been eliminated
- ensures body recognises self antigens and does not stimulate an autoimmune response
Plasma cells
- produce antibodies for a particular type of antigen and release them
- only lives for a few days but v active
B effector cells
divide to form plasma cell clones
B memory cells
- long life span
- ## immunological memory
What do MHC proteins do?
bind to the antigen fragments after a pathogen has been digested by a macrophage and displays the antigens on the csm, making the macrophage an APC
Outline how the structure of an antibody molecule is related to its function. (3)
variable region is antigen binding site; R receptors / ‘sticky ends’ / active site
(shape of) variable region specific to antigen / amino acid sequence (of variable region) gives, complementary / matching, shape;
hinge region allows flexibility in binding / AW;
constant region, for binding to receptors on cells / phagocytes / mast cells;
AVP; e.g. disulphide bonds hold polypeptide chains together
Suggest why the base sequence in the genes for human antibodies is more similar to that found in a chimp than to that found in a mouse. (2)
human and chimp are more closely related;
common ancestor is more recent;
less time for, mutations / variation, to arise;
Name the type of cell that produces antibodies. (1)
plasma/effector cell
State one function for the constant region in an antibody
attach/bind to (receptors on) phagocyte;
State one function for the binding site in an antibody
bind/attach to antigen;
State one function for the disulphide bridge in an antibody
hold, shape/tertiary structure, of molecule; hold (polypeptide) chains together/maintain quaternary structure;
State one function for the hinge region in an antibody
allow molecule to, bend/flex/bind with more than one pathogen;
Explain why the part of the antibody molecule incorporating the binding site is often called the variable region. (2)
different antibodies:
have different amino acid sequence;
have different shape;
fit different antigens;
ref. to specificity/complementary; A lock and key
During an immune response, phagocytic cells are attracted to the site of infection.
Describe the action of these phagocytic cells at the site of infection. (4)
pathogen / bacterium, recognised as foreign;
antigens / pathogen is antigenic;
engulfed / phagocytosis / phagocytosis described / endocytosis;
in, vesicle / phagosome / vacuole;
lysosomes fuse to vesicle;
release, lysins / enzymes / named enzyme;
digest / break down, pathogen / bacterium;
Explain why there is a delay between the first infection by the pathogen and the appearance of antibodies in the blood. (2)
time taken for: antigen presentation; clonal selection; clonal expansion; differentiation (of B cell into plasma cell); production of antibodies;
there are no memory cells;
Describe how antibodies act on invading pathogens, such as bacteria or viruses. (2)
- variable region binds to, antigen / pathogen;
- antigen-binding site variable region specific to, antigen / pathogen;
- antigen-binding site agglutinate pathogens / stick pathogens together;
- immobilise pathogens / attach to flagellum (of pathogen);
- combine with pathogen to stop entry to cell;
- break wall of bacterium open / lysis;
- constant region, attracts phagocytes / makes it easier to engulf bacterium;
In October 2004, scientists announced successful trials of a malaria vaccine. The vaccine was developed from proteins taken from the parasite, ………………………………..
falciparum. When the proteins enter the body they act as ……………………………….. which are recognised as foreign by the immune system. These foreign proteins activate lymphocytes called T cells which then divide to increase in numbers. Some of these newly cloned cells become ……………………………….. cells which attack infected cells in the liver. Others become ……………………………….. cells which release a hormone-like messenger molecule called a ……………………………….. . These molecules activate B
cells to divide and produce plasma cells. The B cells also produce ……………………………….. cells that stay in the body for a number of years. The result is an immune system prepared to make a strong attack on the parasite when it enters the body.
Plasmodium; antigens; cytotoxic / killer / T killer / Tk / Tc; helper / T helper / Th; cytokine / lymphokine; memory;
Name the molecules, released by plasma cells, that attack the parasite when it enters the body. (1)
antibodies/ immunoglobulins
Suggest why it has been difficult to produce a malaria vaccine. (3)
1 several, strains / species, of malarial parasite;
2 parasite is a, protist / protoctist / eukaryote;
3 many surface, proteins / antigens;
4 mutation;
5 ref to antigenic drift / antigens may change;
6 ref to antigenic shift;
7 much of life cycle inside, host cells / red blood cells / hepatocytes;
8 hidden / protected, from immune system; A ref to antigen concealment
What is meant by the word artificial in the term artificial active immunity? (1)
(antigens) injected / taken orally; ora (‘not caught’)
