Topic 6 - Pack 5a And 5b

Question 1

State the four main characteristics of a specific immune response

Answer 1

– It can distinguish between self and non-self
– it recognises and target specific antigens, rather than a general targeting of no self
– it is diverse as it can recognise and target over 10 million different antigens
– it has immunological memory

Question 2

What is an antigen?

Answer 2

A molecule, usually protein or polysaccharide, found on surface of cells or particles.
Recognised by immune system cells as non-self and activate an immune response.

Question 3

When an organism encounter is a specific antigen for the first time what type of specific immune response do they carry out?

Answer 3

Primary immune response

Question 4

Which process in the non-specific immune response initiates the activation of T helper cells? (Initiates specific immune response)

Answer 4

Phagocytosis

Question 5

At the end of phagocytosis what has a macrophage now become?

Answer 5

An antigen presenting cell

Question 6

Describe how a T helper cell is activated in the specific immune response

Answer 6

– A T helper cell with complementary CD4 receptors binds to the antigen on the macrophage APC. The T helper cell becomes activated.
– The activated T helper cell divides/proliferates by mitosis to form clones of the active T helper cells
– Active T helper cells also differentiate and divide to form T memory cells (remain dormant and are used in the secondary immune response when antigen is encountered again)

Question 7

Describe how a B cell is activated

Answer 7

– an antigen on bacterium binds to a complementary shaped receptor on the B cell
– the B cell engulf the bacterium and carries out antigen processing and presentation, antigen is bound to a MHC protein.
– B cell has now become antigen-presenting cell
– an activated T helper cell binds, using its CD4 receptors, to the antigen on the B cell
– the activated tea help cell releases cytokines which activates the B cell and stimulates it to divide by mitosis(this is known as clonal selection)

Question 8

What happens to some of the activated B cells?

Answer 8

Some active B cells differentiate and divide to form B memory cells
– these remain dormant until they are used in the secondary immune response when the antigen is encountered again

Question 9

What happens to other active B cells?

Answer 9

– Other active B cell clones to become B effector cells
– B effector cells differentiate into plasma cells
– plasma cells produce and secrete antibodies
- the binding region on the antibody is the same as a complementary shape as the receptor on the B cell, which bound the original antigen

Question 10

What type of protein are antibodies?

Answer 10

Immunoglobin, form of a globalular protein

Question 11

Describe the main role of antibodies

Answer 11

– Antibodies bind to the complementary antigen on the surface of the pathogen, this is known as opsonisation
– causes pathogens to agglutinate (clump), which helps prevent their spread through the body

Question 12

Describe how antibodies enhance the process of phagocytosis by macrophages

Answer 12

– The constant region of the antibody binds to the antibody receptor on the surface of a macrophage
– the macrophage engulf the antibodies and pathogens into a vacuole, increase number of pathogens are engulfed in the same period of time
– this enhances phagocytosis
– lysosomes fuse with the vacuole, releasing their digestive enzymes that destroy the pathogen

Question 13

Within the specific primary immune response what is the collective activation of tea helper cells and B cells called?

Answer 13

It’s the humoral response

Question 14

What are the two main types of lymphocytes?

Answer 14

T cells and B cells

Question 15

In what situation do T killer cells need to be activated?

Answer 15

When a bacterium or a virus has infected a host body cell

Question 16

Describe how a T killer cells is activated:
the stages from a body cell becoming infected, up to T killer cells dividing by mitosis (stages 1-4)

Answer 16

– A bacterium or virus with antigens on its surface infects a host body cell
– the host cell carries out antigen processing and presentation. Antigen is bound to a MHC protein.
- The host cell has now become an APC
- T killer cell with a complementary receptor binds to the antigen, in the presence of cytokines from active T helper cells, the T killer cell will be activated and stimulated to divide by mitosis

Question 17

What happens to some of the active T killer cell clones, stage four?

Answer 17

Some active T killer cell clones differentiate and divide to form T killer memory cells. These remain dormant until they are used in the secondary immune response when antigen is encountered again.

Question 18

Describe how a killer cell is activated last three steps of the process

Answer 18

– Population of active T killer cell clones created
– active T killer cells bind to other infected host cells which are APCs
– active T killer cell releases enzymes (e.g. perforins ) that create pores in the infected host cell membrane
– water and ions enter cell causing cell lysis, destroying host cell
– any live pathogens within the cell are released
– antibodies find and bind to antigen on pathogen surface for destruction by macrophages in phagocytosis

Question 19

What is the role of macrophages following hostel destruction by the killer cells?

Answer 19

– Macrophages carry out phagocytosis of the agglutinated pathogen, following cell lysis
– they phagocytose host cell debris, following cell lysis