Immune System Flashcards
What is a pathogen
Pathogens are micro-organisms that cause disease
Non-specific defense
-respond to all pathogens in the same way
-act immediately
-2 Forms:
1. barrier to block pathogens
2.phagocytosis
Examples of barriers
- eyes- tears contain lysozymes
- nose- lined with mucus and hairs
3.lungs- Air passages are lined with two types of cells: goblet cells - make mucus
ciliated cells- have cilia
4.skin- outer layer acts as a tough barrier, hair follicles makes sebum
- blood- bloods clots to form a scab
white blood cells- phagocytes - stomach -hydrochloric acid
whats an antigen
-made from protein
-molecules on the cell surface of pathogens/non self cells that trigger the immune response by lymphocytes
or..
-a molecule that is recognised as a non-self by the immune system which triggers an immune response
What might trigger an immune response ?
Glycoproteins
polysaccharides
lipids
nucleic acids
What do these molecules allow the immune system to identify?
- pathogen
2.nonself materials- transplant
3.toxins
4.abnormal body cells like cancer cells
How to minimise the risk of infection?
- donor tissues that are closely matched with recipient- family member if possible
-Immunosuppressant drugs are given to reduce immune response
The recognition of non-self cells
Specific lymphocytes are not produced in response to an infection, they already exist
as there are so many, it is likely that when a pathogen enters the body one lymphocyte will have a protein on its surface that is complementary to one of the antigens on the pathogen.
so the lymphocyte will recognise the pathogen
since there can be so many, there are only small numbers of each type in the body
when an infection occurs the lymphocytes with complementary proteins to those on the pathogen is stimulated to divide
lymphocyte numbers increase
this is called clonal selection
therefore there is a time lag between infection and your defences fighting back
it is also why people become ill or die before their body can mount a defense
Why dont lymphocytes attack our own body cells?
lymphocytes in a fetus are constantly colliding with fetus body cells
some of the lymphocytes have protein receptors that match/ fit the bodies own cells
these lymphocytes either die or are supressed
the only remaining lymphocytes at birth are the ones that will fit non-self material
Where are lymphocytes produced?
in adults lymphocytes are produced in the bone marrow
those that produce an immune response to self antigens undergo apoptosis
this happens before they differentiate into mature lymphocytes
this prevents any appearing in the blood
What is phagocytosis
a mechanism by which phagocytes engulf pathogens to form a vesicle or vacuole
non specific defense
what is a phagocyte
a macrophage (type of white blood cell) that carries out phagocytosis
they are found in blood/ tissues
phagocytosis is a non-specific response meaning that any non-self cell will trigger the immune response
phagocytosis
since pathogens like bacteria are large so they can not cross cell surface membranes
they are therefore englufed by phagocytes and packaged into vesicles made from the cell surface membrane
stages of phagocytosis
Pathogen releases chemoattractants, phagocyte is attracted to the chemoattractants
There are man receptor binding points on the surface of phagocytes, they will attach to chemicals or antigens on the pathogen via these receptors
the phagocyte changes shape to move around and engulf the pathogen
once engulfed the pathogen is contained with a phagosome vesicle
a lysosome within the phagocyte will fuse with the phagosome, Lysozymes are released which hydrolyses the pathogen
This destroys the pathogen
the soluble products are absorbed and used by the phagocyte
What do phagocytes lead to?
phagocytes lead to inflammation at the site of the infection
the swelling contains dead pathogens and phagocytes (puss)
inflammation is caused by histamine
histamine causes dilation of blood vessels
this speeds up the delivery of phagocytes to the site of infection
whats an infection
is the interaction between the pathogen and the bodies various defense mechanisms
what is immunity
the ability to resist infection by protecting against pathogens or their toxins that have invaded the body
specific responses
-slow acting initially
-confers long term immunity to pathogens
-depends upon lymphocytes
two types of lymphocytes
B cells
T cells
T cells- T lymphocytes
mature in the thunus gland
cell mediated immunity/cellular response
immunity involving body cells
responds to foreign material inside body cells
responds to own cells altered by viruses/ cancer or transplanted tissue.
cell mediated response
T-lymphocytes respond to own cells that have been invaded by non self materials
They also respond to material that is genetically different
T cells only respond to to antigens which are presented on cells and not antigens detached from cells and within bodily fluids such as the blood.
The cell mediated response
Once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are positioned on the cell surface. This is now called a antigen presenting cell
Helper t cells have receptors on their surface which can attach to the antigens
once attached this activated the T helper cells to divide by mitosis to replicate and make large numbers of clones
cloned helper t cells differentiate into different cells:
some remain as T helper cells and activate B lymphocytes
some stimulate macrophages to perform phagocytosis
some become memory cells for that shaped antigen
some become cytoxic T cells ( killer T cells)
Cell mediation is needed when
Phagocytes- that have engulfed and hydrolysed a pathogen present some of the pathogens antigens on their surface
Body cells- invaded by a virus present viral antigens on their surface- distress signal
cancer cells - are different from normal cells and present antigens on their surface
transplanted cells - from the same species have different antigens on their cell surface
Cells that display foreign antigens are known as Antigen presenting cells (ATP)
cytoxic T cells
Tc cells kill abnormal body cells
they produce a protein called perforin that makes holes in the cell surface membrane, a hole so that substance can enter/leave the cell
this makes the cell freely permeable, killing it
this action is very effective against viruses as they replicate inside cells. body cells are sacrificed to prevent viral replication
B cells/ B lymphocytes
( b cells are part of the humoral immunity)
- B lymphocytes mature in the bone marrow#
-humoral immunity
-immunity involving antibodies present in bodily fluids (humour)
-antibodies are soluble in blood and tissue fluids
-responds to foreign material outside the body cells
-Theyre aprox 10 million types of B cells
-each type produces a different antibody that responds to different antigens
-T cells respond to antigens that are attached to a body cell, B cells respond to antibodies in humour
-An antigen(protein on the surface of pathogen, toxin, damaged cell) enters the blood or tissue fluid
-it will eventually meet up with the correct B cell that has a complementary antibody on ts surface
-when this happens, the complementary antigen and antibody bind together
-The antigen enters the B cell by endocytosis and is presented on its surface
-Th cells bind to these processed antigens and stimulate this b cell to divide by mitosis
- clones of the b cell are formed that all produce the same specific antibody
-this process is called clonal selection
What can cloned B cells become?
plasma cells
memory cells
plasma cells
-secrete antibodies into blood plasma
-survive for only a few days
-make around 2000 antibodies/sec
-destroy pathogens and toxins
-immediate defence only
-known as primary immune response
memory cells
-can live for decades
-circulate in blood and tissues
-do not produce antibodies
-when they encounter the same pathogen again they divide rapidly into more plasma and memory cells to immediately fight the infection
-This results in large numbers of antibodies being produced so rapidly that the pathogen is destroyed before any symptoms can occur
this is active immunity
The process
-the surface antigens are taken up by the B cell
-B cells process and present these on their surface
-T helper cells attach to the processed antigens on the B cells
- B cells are activated
-The B cells are activated
-The activated B cells now divide by mitosis
Antibodies
-specific binding sites
-produced by b cells
-react with specific antigens
-made of protein
-quaternary structure proteins made up of four polypeptide chains
-each different antibody has different shaped binding site, which is the variable region
-the sequence of amino acids gives each variable region its specific 3D shape
-remainder of antibody is called the constant region.
The role of antibodies
-Do not directly destroy antigens
-different antibodies lead to antigen destruction in a number of ways
Agglutination
-clumps bacterial cells together
-easier for phagocytes to locate and engulf as they are less spread out
markers
-antibodies act as markers that stimulate phagocytes
-phagocytes can easier engulf the pathogen as it is attached
polyclonal antibodies
Pathogens have many antibodies on their surface that can activate b cells
-each of these b cells will clone copies and will produce different antibodies
-these are collectively known as polyclonal antibodies.
Two types of immunity
Passive
active
Passive immunity
-antibodies are introduced from an outside source
-broken down as they arent produced by the individual
-No memory cells
-short lived / no long term immunity
-anti-venom
-immunity acquired by a foetus from mother, through the placenta or through breast milk ( baby)
Active immunity
production of antibodies is stimulated by the individual
-direct contact with the pathogen/antigen
-takes a long time to develop
-long lasting
Two types of active immunity
natural active
artificial active
natural active
Infected with disease
normal immune response
Artificial active
vaccine
induced immune response
few symptoms
How to vaccines result in antibody production
-dead or weakened pathogen is inserted into the body
-the body learns how to fight as the B cell engulfs the antigen
-It then becomes an antigen presenting cell
-T helper cells cause the B cells to divide by mitosis
-plasma cells release antibodies
-some become B cells
-more antibodies are produced more rapidly
How can we make vaccine programmes successful
-Cheap enough
-few side effects
-ability to produce, store and transport
-must be administered correctly at the appropriate time
-vaccinate the majority of the population
Why dont they eliminate disease?
-vaccinations dont induce immunity in some individuals
-disease develops immediately after vaccination before immunity is established
-pathogens mutate frequently
-each pathogen has many varieties
-some pathogens can hide from the immune system
-some people object to vaccinations
Ethics of vaccinations
Animals used in testing
side effects
HIV- how it effects us
-sexual intercourse
-using infected needles
-blood infection of wounds
-blood transfusions
-mother to child ( across placenta or breastmilk )
Symptoms of HIV
-fever
-sore throat
-body rash
-tiredness
-joint pain
-muscle pain
-swollen glands
symptoms of aids
-weight loss
-chronic diarrhoea
-night sweats
-skin problems
-reocurrent infections
serious life threating illness- pnumonia or cancer
Herd immunity
If enough of the population is vaccinated the pathogen cannot spread easily amongst the population
this provides protection for those who are not vaccinated e.g those already to ill to have a vaccine or who have a lowered immunity or those who are too young
Why cant viruses be destroyed by antibiotics
viruses replicate inside of cells - making it difficult to destroy them without harming host cells
viruses also have different mechanisms to replicate and have no cell wall and therefore cant be destroyed by antibiotics
HIV Structure - Core
genetic material (rna) and the enzyme reverse transcriptase, which are needed for viral replication
HIV-structure- CAPSID
outer protein coat
HIV structure - ENVELOPE
extra outer layer, made out of lipids taken from t hosts cell membrane
HIV structure- PROTEIN ATTACHMENTS
on the exterior of the envelope to enable the virus to attach to the hosts t helper cell
HIV replication process
- HIV transported around the blood till it attaches to a attachment protein on the T helper cell
- The HIV protein capsule then fuses with the T helper cell membrane, enabling the RNA and enzymes from HIV to enter
- The HIV enzyme reverse transcriptase copies the viral RNA into a DNA copy and moves the T helper cell nucleus, this is why its called retrovirus
4.Here mRNA is transcribed, and the T helper cell starts to create viral proteins to make new viral particles - New viral RNA and proteins move to the cell surface and a new immature HIV forms
6.Virus is released, viral protease cleaves new polyproteins to create mature infectious virus
HIV to AIDS
HIV positive is when a person is infected with HIV. AIDS is when the replicating viruses in the T helper cells interfere with the normal functioning of the immune system.
With the T helper cells being destroyed by the virus, the host is unable to produce an adequate immune response to other pathogens and is left vulnerable to infections and cancer
it is this destruction of the immune system that leads to death, rather than HIV directly
monoclonal antibodies
- a single type of antibody that can be isolated and cloned
-antibodies are proteins which have binding sites complementary in shape to certain antigens
-this has been manipulated to create monoclonal antibodies for :
medical treatment
medical diagnosis
pregnancy tests
medical treatment- targeted medication
Direct monoclonal antibody therapy
- some cancers can be treated using monoclonal antibodies, which are designed with a binding site complementary in shape to the antigens on the outside of the cancer cells
The antibodies are given to the cancer patient and attach to cancer cells.while the antibodies are bound to the cancer antigens this prevents chemicals from binding to the cancer cells which enables uncontrolled cell growth
Therefore the monoclonal antibodies prevent the cancer cells from growing, and as they are designed to only attach to cancer cells they do not cause harm to other normal cells
medical treatment- targeted medication
indirect monoclonal antibody therapy
cancer can also be treated with monoclonal antibodies complementary in shape to the antigens on the outside of the cancer cells which have drugs attached to them
These cancer drugs are therefore delivered directly to the cancer cells and kill them. This reduces the harmful side effects that traditional chemotherapy and radiotherapy can produce.This is often referred to as bullet drugs.
what does do not include details of cellular response mean?
don’t mention t cells
Th cells are okay
what does do not include details of cellular response mean?
don’t mention t cells
Th cells are okay
which cells can stimulate an immune response
-pathogens
-cells- organisms from the same species
-body cells
-antigen presenting cells
genetic material function in virus
codes for vital protein
capsid function in virus
protects the genetic material
attachment protein function in virus
bind to receptors on cells
structures in a HIV diagram
draw diagram.
transmembrane glycoprotein
attachment glycoprotein
lipid envelope
reverse transcriptase
matrix
capsid
genetic material
antibody diagram
draw diagram
antigen binding site
variable region
constant region
heavy chain
light chain
a cellular organisms
not made of cell
non living
unable to replicate independently
describe how HIV is replicated
- attachment protein attach to receptors on helper T cell
- RNA enters the cell
-reverse transsxripyase converts RNA to DNA
-viral protein produced
-virus particles assembled and released from the
elisa basic
first antibody binds to antigen
second antibody with enzyme attached it added
second antibody attached to antigen
wash fo remove unbound antibody
substrate added and colour change
how do vaccines result in antibody production
- antigen binds to surface receptor on a specific b cell
- activated b cell divides by mitosis
-division is stimulated by T helper cells
-plasma cells release antibodies
-some b cells become memory cells - memory cells can become plasma cells to produce antibodies more rapidly and in a higher concentration on secondary infection.
why are booster vaccines needed
more memory cells produced
so more rapid production of antibodies on further infection on a higher concentration
describe how phagocytosis of a virus leads to presentation of its antigens
a phagosome fuses with a lysosome
the virus is hydrolysed by lysozymes
antigens from the virus are displayed on the cell surface membrane
describe how phagocytosis of a virus leads to presentation of its antigens
a phagosome fuses with a lysosome
the virus is hydrolysed by lysozymes
antigens from the virus are displayed on the cell surface membrane
antigen presenting cells to antibodies
helper t cells binds to the antigen on the APC
helper t cells stimulate a specific b cell
b cells divide by osmosis
forming plasma cells that release antibodies
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