2.4 Immune Response

Created by

kai jones

Cards (51)

What is an immune response?
A series of bodily processes that ensure that any invading pathogen is quickly identified and destroyed before damage is caused to the individual.
What is a pathogen?
A micro-organism that causes disease, they cause disease by damaging host cells and tissues.
What are the two types of responses to infection?
Non-specific response and specific response.
What is a non-specific immune response?
An immediate response of the body that is the same for any pathogen, e.g. phagocytosis.
What is a specific immune response?
A less rapid response of the body to a specific antigen on a specific pathogen, this can be mediated or humoral.
Markers on cell surfaces allow the immune system to tell the difference between:
Self - the body's own cells
Non-self - Any cell that doesn't originate from your body or is infected
What is an antigen?
A protein molecule (can also be glycoproteins) that stimulates an immune response.
What are antibody's produced by and why?
They're protein molecules that are produced by B plasma lymphocytes in response to a specific non-self antigen.
Antibodies have a specific tertiary structure. The shape of the antigen binding site on the antibody is complementary to the antigen, the antigen binds to the antibody to form an antigen-antibody complex.
Fill in the following antigen-antibody complex diagram:
A) Variable Regions
B) Antigens
C) Hinge Protein
D) Constant Regions
E) Disulphide Bridge
F) Heavy Chain
G) Light Chain
H) Antibody
What is a phagocyte?
A type of white blood cell.
What happens during phagocytosis?
The chemical products of the pathogen attract the phagocytes causing them to move towards it. Phagocytes attach to the pathogen surface using receptors, they then engulf the pathogen to form a vesicle called a phagosome. Lysosomes move towards the phagosome and fuse with it to form a phagolysosome, the lysosomes release enzymes called lysozymes into the phagolysosome to digest the pathogen by hydrolysis. Finally, pathogen antigens are presented on the cell membrane of the phagocyte.
What is a cell mediated response?
This is a response to non-self antigens presented by the body’s own cells that have engulfed/been infected with a pathogen or are cancerous (all known as antigen presenting cells). This response does not involve antibody production, only involving T lymphocytes.
What is a humoral response?
This is a response to non-self antigens like viral or bacterial infections in the blood, this produces antibodies to kill the pathogen, which are protein molecules soluble in the body’s ‘humours’ (blood and tissue fluid). This response involves B and T lymphocytes.
What are Lymphocytes?
They're specific types of white blood cells which are formed from stem cells and found in bone marrow.
Where do T cells mature?
In the thymus gland
Where do B cells mature?
In the bone marrow
What are the two types of lymphocytes?
T cells and B cells
How do antibodies lead to the destruction of a pathogen?
They cause the pathogen to clump together, in a process called agglutination. This means that viruses can’t bind or enter cells, they act as markers to stimulate phagocytosis
Memory cells:
B or T memory cells can be stored in the body’s lymph nodes.
Years later when they encounter the same pathogen with the same antigen, they are re-activated.
B memory cells can then divide and differentiate into B plasma cells to produce antibodies.
What is a vaccine?
It is an attenuated form of an antigen, it contains antigens which stimulate the production of antibodies and memory cells in the body.
On infection with the pathogen they provide a secondary response with more antibodies produced faster.
Name the two types of immunity.
Passive-produced and active-produced
What is passive-produced immunity?
This is the introduction of antibodies into an individual from an outside source, these antibodies are not produced by the individual e.g. antibodies passed from mother to baby in breast milk or antivenom. This immunity is faster but short lived
What is active-produced immunity?
This is stimulating the production of antibodies by the individual’s own immune system, like the clonal selection and expansion followed by differentiation of B cells into plasma cells and the secretion of antibodies. This immunity is slower but longer lasting. This is the type of immunity that is stimulated by vaccines.
Why do antigens change rapidly on bacteria and viruses?
This is due to mutations, specifically, changes to DNA/RNA base sequences of a gene).
Why are frequent mutations in bacteria or viruses bad?
This can cause antigens on the bacteria/virus to change, due to this, the antibody is no longer complementary so no antibody-antigen complexes form and memory cells will no longer recognise the antigen.
Suggest and explain how the new virus variants came about, and why the vaccines are ineffective against them.
A mutation occurred in the viral RNA altering the tertiary structure of the viral attachment protein resulting in antibodies not being complementary to the new attachment protein.
What is herd immunity?
When the majority of a society is vaccinated or immune.
Does this data support the hypothesis that MMR causes autism?
There is an increase in autism after the MMR vaccination, however, it had already started increasing before then so the increase may be due to other factors like better diagnosis.
Why are control groups used in vaccine trails?
They used to show that the vaccine is causing a decrease in the incidents of disease and not another factor. They will inject a placebo and then treat the control group in the the exact same way.
Some graphs represent data in per 100,000 of the population, this is done to allow comparison as other countries may have a larger or smaller population.
Describe the process of HIV replication.
The attachment protein binds to a receptor on the host helper T cell membrane.
The capsid enters the cell, uncoats, and releases RNA into the cytoplasm.
Reverse transcriptase creates a complementary DNA strand from the viral RNA.
Double-stranded DNA is made and inserted into the human DNA.
Host cell enzymes and ribosomes produce viral proteins from the viral DNA found within the human DNA
Viral proteins are assembled into new viruses, which leave the cell by budding as it is wrapped in a lipid envelope and infects other cells.
HIV causes the symptoms of AIDS by infecting CD4 T helper cells leading to low numbers of T helper cells in the blood. As a result T helper cells cannot bind to foreign antigens meaning they cannot stimulate: cytotoxic T cells, phagocytosis, or stimulate B cells to divide. This results in no antibodies being made.
AIDS prevents the stimulation of phagocytosis, B cells and cytotoxic T cells. What happens due to this?
Memory cells can become infected or destroyed.
Pathogens can reproduce without an immune response so sufferers become susceptible to opportunistic infections.
Many experience weight less and diarrhoea.
Many develop infections of the lungs, intestines, brain and eyes.
What are the three stages of HIV in order?
Acute infection, clinical latency and AIDS.
Describe the acute infection stage of HIV.
During this time, large amounts of the virus are being produced in your body. Many, but not all, people develop flu-like symptoms often described as the “worst flu ever”.
Describe the clinical latency stage of HIV.
During this stage, HIV reproduces at very low levels, although it is still active during this period, you may not have symptoms. With proper HIV treatment, people may live with clinical latency for several decades. Without treatment, this period lasts an average of 10 years, but some people may progress through this stage faster than others.
Describe the AIDS stage of HIV.
As your CD4 cells fall below 200 cells/mm3, you are considered to have progressed AIDS. Without treatment, people typically survive 3 years.
Why are antibiotics ineffective against viruses?
Most antibiotics work by interfering with the formation of the bacterial cell wall. This means that there is nothing to withstand the high pressure caused by osmotic entry of water into the cell. Because viruses don’t have a cell wall antibiotics are useless and viruses are also inside of host cells where antibiotics can’t reach them.
Why is is difficult to produce vaccines against HIV?
HIV shows a lot of antigenic variability:
When the virus RNA mutates the antibodies will no longer be complementary to the antigens and it will not be recognised by memory cells. There are also lost of different strains of HIV, meaning that it’s not possible to create a vaccine for all the different antigens.
Why are treatments involving monoclonal antibodies specific?
They have a specific sequence of amino acids in their primary structure which generates a specific tertiary structure. The binding site only binds to antigens that have a complementary shape so when they do bind a antigen-antibody complex is formed. Due to this it will not bind to other antigens.