2.4 cell recognition and the immune system

Describe how HIV is replicated

1 - attachment proteins attach to receptors on helper T cell

2 - nucleic acid/RNA enters cell

3 - reverse transcriptase converts RNA to a DNA copy

4 - viral protein/ capsid/ enzymes produced

5 - virus (particles) assembled and released (from cell)

use ur knowledge of phagocytosis to describe how an ADC enters and kills the tumour cell

• cell ingests/ engulfs the antibody (ADC)

• lysosomes fuse with vesicle/ phagosome (containing ADC)

• lysosomes breakdown/digest the antibody/ADC

antigens found on surface of tumour cells are also found on surface of healthy human cells. explain why treatment with an ADC often causes side effects.

ADC will bind to non-tumour/ healthy cells

causing death/damage of non tumour/ healthy cells

how is HIV replicated once inside the helper T cell

RNA converted into DNA using reverse transcriptase

DNA inserted into helper T cell DNA

DNA transcribed into HIV RNA

HIV mRNA translated into new HIV/viral proteins

describe how a phagocyte destroys a pathogen present in the blood

engulfs pathogen

forming a vesicle/phagosome and fuses with a lysosome

enzyme in lysosome digest/hydrolyse

what is the role of the disulphide bridge in forming the quaternary structure of an antibody

joins two different polypeptides

Explain how HIV affects the production of antibodies when aids develops in a person

less/no antibody produced

because HIV destroys T helper cells

so few/ no B cells activated

During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom.
Use your knowledge of the humoral immune response to explain this vaccination
programme.

B cells specific to the venom reproduce by mitosis;
(B cells produce) plasma cells and memory cells;
The second dose produces antibodies (in secondary immune response) in higher concentration and quickly
OR
The first dose must be small so the animal is not killed;

when a vaccine is given to acquire active immunity

1) vaccine contains antigens (usually dead) from the pathogen

2) antigen is engulfed by a phagocyte and the antigen is then presented on the cell surface membrane

3) T helper cell with a complementary receptor binds to the antigen

4) T helper cells stimulate a specific B cell (with complimentary antibodies)

5) B cell clones and differentiates

6) plasma B cells release large numbers of antibodies

7) memory cells remain in the body

passive immunity

short lived

antibodies gradually broken down

no memory cells produced

antibodies not replaced

active immunity

longer lasting

memory cells are produced in response to the antigen

memory cells remain in circulation

memory cells release antibodies rapidly