(2) cells: cell recognition and the immune system

Question 1

what are the 2 types of immune system response?

Answer 1

non specfic: inflammation, phagocytosis, interferons, lysozymes
specific: T-cells, B-cells (antibodies)

Question 2

what is a lysozyme?

Answer 2

an enzyme that disrupts the cell walls gram-positive bacteria by digesting the peptidoglycan
found in human tears, saliva and lysosomes

Question 3

what are interferons?

Answer 3

proteins produced by virus-infected body cells in response to the vrius
trigger the production of a second protein that inhibits viral replication by binding to mRNA coded by the virus

Question 4

how does inflammation work as a localised response?

Answer 4

1. tissue = damaged and pathogens may enter body, damaged cells will release chemical substances (histamines) which acts as inflammatory mediators
2. chemicals cause an increase in blood and permeability of the capillary, area becomes flooded with fluid and blood-clotting elements causing swelling n redness
3. tissue cells also release chemicals (e.g chemokines) that attract phagocytic white blood cells such s as neutrophils and macrophages
4. phagocytosis begins when macropjages recognise invading bacteria as pathogens
5. cell membrane of the macrophages fuses around a single bacterium, trapping it inside a phagosome
6. the phagosome fuses with a lysosome to form a phagolysosome and the bacterium is broken down and killed
7. when the bacterium is destroyed, the macrophage absorbs any useful material and expels the rest through exocytosis
8. as pathogens are destroyed, anti-inflammatory factors begin to work so inflammation doesn’t continue longer than is necessary
   swelling will reduce and skin will eventually heal

Question 5

how is a phagolysosome formed?

Answer 5

• phagocytic cell is attracted to pathogen by chemical trail
• receptors on phagocyte attach to antigens on pathogen
• membrane infolds and lysosomes migrate towards the phagosome
• lysosomes fuse w phagosome to form phagolysosome
• pathogen digested by lytic enzymes

Question 6

what are the characteristics of specific immune response and what are the main 2 types?

Answer 6

it can target a specific pathogen
slower to act than the non-specific response

cell mediated response
humoral / antibody mediated response

Question 7

what are lymphocytes?

Answer 7

white blood cell found in the blood and lymph nodes
produced by stem cells in bone marrow

2 types: T cell, B cell

Question 8

what is the role of helper T cells?

Answer 8

acts as a ‘co-ordinator’ of the immune response

when a pathogen is detected, helper T cells produce a chemical signal resulting in the proliferation of specific cytotxic T cells and effector B cells

activates B cells and helps produce memory cells

Question 9

what is the role of cytotoxic T cells?

Answer 9

recognises infected cells/tumour cells
destroys them by secreting proteins that rupture their membranes, causing the cell to lyse

Question 10

what is the role of effector B cells?

Answer 10

• multiply and give rise to plasma cells when activated by helper T cells
  may become memory B cells

Question 11

what is the role of plasma cells?

Answer 11

develop from effector B cells
produce large amounts of antibodies, which bind to a pathogen and cause it to be destroyed or inactivated

Question 12

what is the role of memory cells?

Answer 12

circulate in the blood after the pathogen has been removed
if stimulated, they divide and rapidly produce a secondary immune response

Question 13

what happens during the cellular mediated response?

Answer 13

1. when a macrophage destroys a pathogen by pathogen by phagocytosis, it will display a pathogens antigen on its cell surface: becomes an antigen presenting cell
2. APC interacts w specific helper T cell and releases a chemical substance called interleukin 1 ( cytokine [chemical involved in cell signalling])
3. interleukin 1 stimulates helper T cell to release another cytokine (interleukin 2) which stimulates the growth and development of antigen specific cytotoxic T cells
4. Cytotoxic T cell detect the antigen on the surface of the infected body cells and produce perforin; it forms pores in te target cell’s membrane, allowing ions and water in and causing the lysis of the cell
5. exposure to a specific antigen results in memory T cells being produced, ready to initiate a response to the same pathogen if the body becomes infected again in the future

Question 14

what happens during a humoral immune response?

Answer 14

1. when a macrophage destroys a pathogen by pathogen by phagocytosis, it will display a pathogens antigen on its cell surface: becomes an antigen presenting cell
2. APC interacts w specific helper T cell and releases a chemical substance called interleukin 1 ( cytokine [chemical involved in cell signalling])
3. interleukin 1 stimulates helper T cell to release another cytokine (interleukin 2) which stimulates the differentiation of effector B cells into plasma cells
4. the plasma cells divide and produce large quantities of antigen-specific antibodies: these attach to the pathogen and destroy it by neutralisation/agglutination
5. exposure to a specific antigen results in memory B cells being produced, ready to initiate a response to the same pathogen if the body becomes infected again in the future

Question 15

what are the components of an antibody?

Answer 15

antigen binding site
disulphide bonds
polypeptide chains
constant regions
variable regions

Question 16

what are the characteristics of the antigen binding site?

Answer 16

enables the antibody to bind a specific antigen on pathogen
results in the pathogen being destroyed by the cells of the immune system

Question 17

what are the characteristics of the disulphide bonds?

Answer 17

holds the 4 polypeptide chains of the anti-body structure together
strong covalent bonds that occur between 2 cysteine amino acids

Question 18

what are the characteristics of the polypeptide chains?

Answer 18

2 identical light chains
2 identical heavy chains

Question 19

what are the characteristics of the constant regions?

Answer 19

amino sequence in them varies only slightly between different antigen-specific antibodies

Question 20

what are the characteristics of the variable regions?

Answer 20

amino acid sequence = different in each specific type of antibody
forms unique shape and specificity of the antibody’s antigen-binding site

Question 21

what is active immunity?
what is an example of
a) natural active
b) artificial active

Answer 21

immunity that is acquired through the production of antibodies in response to an infection or through vaccination
(memory cells are present, 1-2 weeks before antibodies appear in the bloodstream)
a) infection
b) vaccination

Question 22

what is passive immunity?
what is an example of
a) natural passive
b) artificial passive

Answer 22

immunity that is acquired through the transfer of antibodies from one individual to another
(memory cells not present, immediate)
a) maternal (Fetus’ receive antibodies across the placenta from their mothers, babies receive the initial breast milk from mothers)
b) monoclonal antibodies, antivenom

Question 23

what is a vaccine?

Answer 23

suspension of weakened or dead form of a pathogen to a person, in order to trigger the production of antibodies

produces long-term immunity as they cause memory cells to be created. The immune system remembers the antigen when reencountered and produces antibodies to it, in what is a faster, stronger secondary response

Question 24

what is HIV?

Answer 24

human immunodeficiency virus
causes AIDS ( acquired immunodeficiency syndrome)

Question 25

what are the features of a HIV?

Answer 25

attachment glycoprotein: complementary to the CD4 on a T helper cell

lipid bilayer envelope: contains glycoproteins

capsid: contains RNA and enzymes necessary for replication, protects RNA

viral RNA: codes for viral proteins

reverse transcriptase/intergrase: converts RNA to DNA

Question 26

what happens during HIV replication?

Answer 26

1. HIV recognised and binds to receptors (CD4) on the surface of the T helper cell via its glycoproteins
2. the virus fuses with the cell membrane of the Th cell and the viral RNA enters the cell
3. the viral RNA is converted to DNA via reverse transcriptase, before being made double stranded and entering the nucleus
4. MRNA is produced from the DNA (used to synthesise viral proteins )
5. a new copy of viral RNA is also made and a new virus particle buds off from the helper t cell, taking a piece of host membrane to form its envelope
6. HIV replication results in T cell death
7. overtime the loss of Th cells damaged the immune system

Question 27

what happens during HIV replication?

Answer 27

1. HIV recognised and binds to receptors (CD4) on the surface of the T helper cell via its glycoproteins
2. the virus fuses with the cell membrane of the Th cell and the viral RNA enters the cell
3. the viral RNA is converted to DNA via reverse transcriptase, before being made double stranded and entering the nucleus
4. MRNA is produced from the DNA (used to synthesise viral proteins )
5. a new copy of viral RNA is also made and a new virus particle buds off from the helper t cell, taking a piece of host membrane to form its envelope
6. HIV replication results in T cell death
7. overtime the loss of Th cells damaged the immune system

Question 28

what is the effect of HIV on the immune system?

Answer 28

1. causes flu like symptoms and shri bc this time the Th cell count halves
2. after 12 weeks the virus becomes interstates into the Th cells genome (cytogenic cycle) and slowly decreases Th cell count over a number of years
3. the immune system has problems fighting basic diseases, illnesses will be fatal

Question 29

what is antigen variability?

Answer 29

pathogens can change their surface antigens
mens when ur infected a second time the memory cells produced from the first infection will not recognise the different antigen and will have to produce the primary response again