Immunity (Topic 2)

Question 1

Antigens

Answer 1

Molecules on cell surfaces that can stimulate an immune response
Allow the immune system to see the difference between self cells and non self cells

Non self are foreign, and the immune system identifies these.

Question 2

What are the 4 things that antigens enable the immune system to identify?

Answer 2

Pathogens
Toxins
Abnormal body cells
Cells from other organisms of the same species

Question 3

Antigenic variability

Answer 3

Mutation in DNA sequence of pathogen -> change in amino acid sequence (primary structure) -> changes locations in which bonds form; change in tertiary structure, antigen changes shape.
Previous immunity not effective: memory cells don’t recognise new antigen.

Question 4

Which white blood cells are involved in the:
A) non specific response
B) specific response

Answer 4

A) phagocytes
B) lymphocytes (T cells and B cells)

Question 5

Describe the process of phagocytosis

Answer 5

Phagocyte identifies foreign antigen on pathogen
Phagocyte attaches to antigens via receptors and engulfs the pathogen
Pathogen contained in a phagosome
Lysosome fuses with phagosome
Releases lysozyme which hydrolyses + destroys the pathogen

Phagocyte presents the antigens on it’s surface: becomes an APC

Question 6

Role of lysosomes in phagocytosis

Answer 6

Lysosomes fuse with the phagosome and release lysozyme to hydrolyse the pathogen

Question 7

Why is phagocytosis a non specific response

Answer 7

Any phagocyte will attach to any antigens on any pathogen

Question 8

Name the two specific immune responses and which cells are involved in them

Answer 8

Humoural and cell mediated

Humoural = B cells
Cell mediated = T cels