the third line of defence

Question 1

what is the third line of defence

Answer 1

the specific response= the primary immune system response by B and T lymphocytes to kill pathogens and infected cells to destroy infection

Question 2

what is an antigen

Answer 2

a substance which is recognised as foreign by the immune system therefore stimulating the immune response

1) they have a specific shape on the surface of bacteria or viruses
2) can be free molecules such as toxins
3) each pathogen has its own unique antigens which are genetically determined

Question 3

what is an antibody

Answer 3

a large protein molecule which recognises and neutralises antigens

Question 4

outline the structure of an antibody

Answer 4

specific shape complementary to the particular antigen
quaternary structure made-up of 2 heavy and 2 light chains
aka immunoglobulins

Question 5

what are the different ways antibodies can combat pathogens

Answer 5

1) neutralisation

2) agglutination

Question 6

outline agglutination

Answer 6

the formation of an antibody-antigen complex causing the pathogens to be held together in large clumps

macrophages and neutrophils can more easily engulf pathogens as they are immobilised

Question 7

outline neutralisation

Answer 7

antigens which produce toxins are rendered harmless as the antibody blocks them by binding

Question 8

what is opsonisation

Answer 8

1) a way of identifying the invading particle to the phagocyte
the pathogen is parked by an antibody for phagocytosis

Question 9

what responses make up the specific immune response

Answer 9

1) humoral- B lymphocytes via antibodies

2) cell mediated- T lymphocytes- direct contact with cells

Question 10

outline a B lymphocyte

Answer 10

1) matures in the spleen and lymph nodes
2) develops into B cells which secrete antibodies and Memory B cells which remain in the body for years and act as immunological memory

Question 11

outline a T lymphocyte

Answer 11

1) migrate to the thymus gland to mature
2) develop into
- T helper cells= release cytokines which stimulate B lymphocytes to develop and stimulate phagocytosis
- T killer cells- attack and kill infected cells
- T memory cells