Communicable diseases- specific immune response

Question 1

what are antibodies?

Answer 1

glycoproteins called immunoglobulins which bind to a specific antigen or toxin.

Question 2

describe the structure of an antibody

Answer 2

Y shape, made of two identical polypeptide chains called heavier chains and lighter chains which are short. The chains are linked by disulphide bonds. The variable region is different on each anti-body allowing it to be specific. When an antigen binds with an antibody, a antigen-antibody complex is formed. The rest of the antibody molecule is the same so it is called the constant region.

Question 3

how do antibodies defend the body? (4 points)

Answer 3

1) the antibody acts as an opsonin so the complex is easily engulfed and digested by phagocytes
2)pathogens can’t invade host cells when antigen-antibody complex is formed.
3)antibodies act as agglutinins causing the antigen-antibody complexes to clump together which prevents the spread of the pathogen and makes it easier for the phagocyte to digest the pathogen.
4)anti-bodies act as anti-toxins, making the toxins harmless

Question 4

what does the specific immune system rely on?

Answer 4

lymphocytes

Question 5

where do B and T lymphocytes mature?

Answer 5

B lymphocytes mature in the bone marrow and T lymphocytes mature in the thymus gland

Question 6

What are the main types of T lymphocytes?

Answer 6

T helper cells, T killer cells, T memory cells, T regulator cells

Question 7

Describe T helper cells

Answer 7

They have CD4 receptors which bind to antigens on APCs producing interleukins which are a type of cytokine (cell signalling molecule). These stimulate the activity of specific B cells, increasing antibody production and other T cells and macrophages to ingest pathogens with the antigen-antibody complex.

Question 8

Describe T killer cells

Answer 8

-destroy pathogen carrying its antigen
-produces perforin chemical which kills pathogens by making a holes in the membrane

Question 9

Describe T memory cells

Answer 9

part of the immunological memory. If they meet the same antigen again, they divide rapidly to form clones of T killer cells.

Question 10

Describe T regulator cells

Answer 10

-control and regulate immune system
-suppresses other cells in immune system when pathogen is defeated
-makes sure body recognises self antigens and doesn’t set up an autoimmune response. Interleukins are important for this.

Question 11

What are the main types of B lymphocytes?

Answer 11

Plasma cells, B effector cells and B memory cells

Question 12

Describe plasma cells

Answer 12

produce antibodies to a particular antigen and release them into the circulation. They only live for a few days but produce many antibodies.

Question 13

Describe B effector cells

Answer 13

divide to form plasma cell clones

Question 14

Describe B memory cells

Answer 14

-immunological memory
-remembers specific antigens and has a rapid response when encountered again

Question 15

why are the cell mediated response important against viruses and early cancers?

Answer 15

because in cell mediated response, T lymphocytes respond to cells which have been changed in some way

Question 16

Describe the steps in the cell mediated response

Answer 16

1)When macrophages go through phagocytosis, they process the antigens to the surface forming antigen presenting cells (APCs)
2)The specific T helper cells produces interleukins, which stimulates the division of more T cells by mitosis.
3)then the cloned T cells may:
-develop into T memory cells
-produce interleukins to stimulate phagocytosis
-produce interleukins to stimulate B cells to divide
-stimulate the development of a clone of a T killer cell which is specific to the antigen

Question 17

Describe humoral immunity

Answer 17

body responds to pathogens found outside cells e.g bacteria and fungi. The humoral immune system produces antibodies which are soluble in blood and are not attached to cells.

Question 18

Describe the steps in the humoral immunity response

Answer 18

1)activated T helper cells bind to the B cell APC. Clonal selection occurs-specific B cells clones.
2)interleukins produced by the activated T helper cells activate the B cells
3)activated B cells divide by mitosis to give clones of plasma cells and B memory cells- clonal expansion.
4)Plasma cells produce specific antibodies which disable pathogens or they act as opsonins and agglutinins. This is a primary immune response.
5)If the body is infected with the same pathogen again, B memory cells divide to form plasma cells rapidly. This is a secondary immune response.

Question 19

what is an autoimmune disease?

Answer 19

disease in which immune system stops recognising ‘self’ cells and starts to attack healthy body tissue. E.g type 1 diabetes, rheumatoid arthritis and lupus.

Question 20

why is developing a vaccine for HIV difficult?(3marks)

Answer 20

-protected by self antigens (antigenic concealment)
-viruses have high mutation rate
-strains have different antigens

Question 21

what is the difference between a neutrophil and macrophage?

Answer 21

-neutrophil has multi lobed nucleus, macrophage has rounded
-macrophage has MHC complex but neutrophils don’t

Question 22

what is an antigen-presenting cell?

Answer 22

cells that present a non-self antigen on their surface

Question 23

Antigen-presenting cells include what

Answer 23

-infected body cells presenting viral antigens on their surface
-a macrophage which has engulfed and destroyed a pathogen presenting the antigens on their surface
-cells of a transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens
-cancer cells will have abnormal-shaped self antigens