Cell recognition and the immune system

Question 1

What is a pathogen?

Answer 1

A pathogen is a microorganism that causes disease

Question 2

What is an antigen?

Answer 2

Each type of cell has specific molecules on its surface that identifies it. These molecules include proteins and enable the immune system to identify pathogens.

Question 3

What type of defences does the human body have?

Answer 3

It has the non-specific immune response, which is general and immediate a barrier to entry which is the skin tears earwax or mucus and also phagocytosis we don’t have the specific immune response which is less rapid but long lasting which includes the cell mediated response involving T lymphocytes and the humoral response involving being lymphocytes

Question 4

What is the process of phagocytosis?

Answer 4

Firstly the phagocytes recognise antigens on the pathogens as foreign and engulfs into a called a phagosome. This is endocytosis then a lysosome fuses with the phagosome and releases Lysozymes into it. Lysozymes hydrolyse the pathogen and the harmless products of digestion or absorbed by the pathogen or released by exocytosis antigens from the pathogen are displayed on the cell membrane turning it into an antigen presenting cell.

Question 5

What is an antigen presenting cell?

Answer 5

Any cell that represents a non-self antigen on their surface for example infected body cells represent the viral antigens on their surface

Question 6

What is the cell mediated response?

Answer 6

Firstly pathogens invade the body cells and then the cells become antigen-presenting cells as they place the pathogen antigens onto their self service membrane. This means that the receptors on a specific T help a cell fit exactly onto these antigens and then this activates the T helper cell to divide rapidly by mitosis and form a clone of genetically identical cells so then these clones to help cells stimulate the correct cells to divide and secrete antibodies. They also stimulate phagocytes to engulf more pathogens and they activate killer cells which activate toxic cells to destroy infected cells.

Question 7

What is the humoral response?

Answer 7

A pathogen invades the body and then an antibody on the surface of a B cell bind to a specific antigen and forms antigen antibody complex this along with the chemicals from the help cell activate the B cell by releasing cyclines. This is colon selection the activated B cell divided by mitosis into plasma cells and memory cells. Plasma cells are clones of the bi cell which the specific monoclonal antibody Antibody transported by blood to the site of infection antibody combined with the antigen and the surface of pathogenic cells to produce an antibody antigen complex. This stimulates phagocytosis of the pathogen the memory B cells remain in the body for many years they can reproduce rapidly to produce an incident supply of plasma cells if the same pathogen based the body Again.

Question 8

What is an antibody?

Answer 8

It is proteins made by B cells. They bind to specific antigens to calm them together aid phagocytosis

Question 9

What does the constant region do? And what does the variable region do?

Answer 9

The constant region has the same sequence of amino acid which means it is the same primary structure and the variable region has a specific territory structure which is complementary to one antigen so is the antigen binding site

Question 10

What is the hinge region?

Answer 10

The hinge region is made so that antibodies combined more easily with aptitude antigens forming an antigen antibody complex.

Question 11

What is agglutination?

Answer 11

It means clumping together this slows the pathogen down to enable phagocytosis

Question 12

What is the primary immune response?

Answer 12

It is the first time that an individual comes into contact with a particular antigen slower as there aren’t many specific B cells to produce specific antibodies. The patient will develop symptoms as the pathogen increases a number and damage cells B cells and T cells produced memory cells which remained in the body for a long time.

Question 13

What is the secondary immune response?

Answer 13

It is his next time that the individual comes into contact with the antigen colon selection is much faster more antibodies are produced in a short space of time. Rapid response prevent infection so person is immune

Question 14

What is immunity?

Answer 14

Immunity is the ability of an organism to resist infection and it takes two forms

Question 15

What is active immunity?

Answer 15

It is when the immune system makes his own antibodies and it requires exposure to antigens and it takes a while for protection to develop long-term as memory cells produced

Question 16

What is passive immunity?

Answer 16

Given antibodies from elsewhere example children from their mothers it does not require exposure to antigen. It gives immediate protection but it’s short-term as memory cells aren’t produced.

Question 17

What is natural passive immunity and what is artificial passive immunity?

Answer 17

Natural passive immunity is when antibodies passed through the placenta or breastfeeding artificial passive immunity is antibodies injected into someone who has been infected with a dangerous disease. They have no immunity example bitten by a snake.

Question 18

What is natural active immunity and what is artificial active immunity?

Answer 18

Natural active immunity is just the results from an infection by the disease and artificial active immunity is vaccination

Question 19

What is the process of vaccination?

Answer 19

The vaccine contains the antigen which is usually a weak form of the pathogen. This stimulates the production of APC specific helper tea cells detect the antigen and this stimulate specific B cells. These B cells divided by mitosis to give plasma cells which produce antibodies and memory cells. A second dose could produce antibodies in a secondary immune response in higher concentration and quickly.

Question 20

What is herd immunity?

Answer 20

Interrupts transmission to a population if enough of the population of vaccinated the pathogen cannot easily spread through the population. This provides protection for those who cannot be vaccinated those who are too ill or too young or who have lowered immunity.

Question 21

How can vaccine control disease ?

Answer 21

Provides artificial active immunity with memory cells
Most children are vaccinated young
Herd immunity interrupts transmission through a population

Question 22

What are the ethical issues with vaccines ?

Answer 22

Use of testing on animals in development and production
Risk to people in medical trials
Expense
Priorities on who should get the vaccine first

Question 23

What is antigenic variability ?

Answer 23

Some pathogens can change their surface antigens
Virus mutates
Primary response each time as no memory cells for new antigen
Enables pathogen to evade recognition

Question 24

What are monoclonal antibodies ?

Answer 24

A single type of antibody with the same shape and 3D structure produced from a single clone of plasma cells

Question 25

What are the uses of monoclonal antibodies ?

Answer 25

Medical treatment Cancer cells have antigens called tumour markers not found on normal body cells Specific monoclonal antibodies can bind to tumour markers You can attach anti cancer drugs to the specific antibodies Drugs will only accumulate where there are cancer cells reducing side effects they are also often called bullet drugs Medical diagnosis

Question 26

How do pregnancy tests work ?

Answer 26

Antigen binds to complimentary specific antibodies in result window Mobile antibodies also bind to antigen Build up of the mobile antibodies, builds up the blue dye and creates a visible line Mole antibodies bind to complimentary antibodies in control window. Build up creates blue visible line

Question 27

What are the four different parts of a pregnancy tests and what happens at each stage ?

Answer 27

1. Urine is applied here 2. Reaction zone, there are mobile antibodies specific to HCG here. These antibodies can move and have blue dye attached to them. 3. Result window immobilised antibodies specific to HCG here 4. Control window, immobilised antibodies specific to the mobilised antibodies from the reaction zone

Question 28

What is the ELISA test ?

Answer 28

Medical diagnosis test to detect specific antigens or antibodies in blood

Question 29

What is the process of the ELISA test ?

Answer 29

An antigen is attached to the test well The blood/plasma sample is added. Any complimentary antibodies bind to the antigen. Well is washed. A second antibody with an enzyme attached. It binds to the first antibody if it is present and attached to the antigen. Well is washed. A yellow substrate solution is added. If the enzyme linked antibody is present then it turns into a blue product. A control well is also used with salt solution to show that only the enzyme is causing the colour change and that washing the unbound antibody is effective

Question 30

What is the structure of HIV ?

Answer 30

RNA, the core contains genetic material and some proteins (reverse transcriptase) Capsid, outer protein coating Envelope, made of membrane fr9m a previous host cell Attachment proteins, stick out from the envelope and attach to host helper T cells

Question 31

How does HIV replicate inside T cells ?

Answer 31

Attachment proteins attach to receptor molecules on the host helper T Cell Capsid is released into the cell, it un-coats, then releases RNA into the cytoplasm Reverse transcriptase makes a complimentary strand of DNA from the viral RNA template This makes a double stranded DNA which is inserted into the host cell human DNA Host cell enzymes are used to make viral proteins and RNA which are assembled into new viruses These new virus bud from the cell and infect other cells

Question 32

HIV causes the symptoms causes AIDS

Answer 32

Helper T cell count drops The immune system deteriorates and eventually fails The person is then more vulnerable to other infections Antibiotics don’t work, as only kill bacteria interfering with their cell wall, metabolism and enzymes. Viruses don’t have a cell wall and only use human metabolism and enzymes

Question 33

What can help reduce the effects of viruses ?

Answer 33

Antiretroviral drugs- drugs which prevent the infection or replication of viruses Shown to dramatically decrease the virus load in HIV positive individuals to undetectable levels May not be effective against dormant HIV just HIV that is actively replicating Pre exposure prophylaxis the taking of art by sexually actively adults to prevent the infection by HIV

Question 34

How do antibiotic kill bacteria ?

Answer 34

Prevention cell replication Preventing protein synthesis Preventing DNA replication Preventing cell wall synthesis These don’t work on HIV as its a virus and doesn’t have a cell wall HIV doesn’t replicate it goes inside the cell Doesn’t have DNA it has RNA