Immunology

Question 1

What are pathogens?

Answer 1

disease causing microorganisms that release toxins that kill cells

Question 2

What is an antigen?

Answer 2

protein molecule that triggers an immune response by lymphocytes
eg pathogen, toxins, abnormal body cells

Question 3

What blood cells are involved in non specific immunity?

Answer 3

phagocyte

Question 4

What blood cells are involved in specific immunity?

Answer 4

B-lymphocytes and T-lymphocytes

Question 5

Describe the process of phagocytosis

Answer 5

phagocyte recognises antigens on pathogen as non self
phagocyte engulfs pathogen
a phagosome forms around the pathogen (vesicle)
a lysosome fuses with the phagosome then releases lysozymes to hydrolyse the pathogen and it is digested
the macrophage presents the pathogens antigens on their surface membrane to become an antigen presenting cell

Question 6

What is an antigen presenting cell?

Answer 6

cells that display non self antigens on their surface to activate other immune cells

Question 7

How do T lymphocytes work?

Answer 7

T helper cell receptors bind to non self antigen
divide by mitosis
release cytokines which activates specific b cells and cytotoxic T cells
cytotoxic T cell receptor binds to APC and divide by mitosis
release perofin which kills the apc or pathogen

Question 8

How do B lymphocytes work?

Answer 8

divide by mitosis when activated
form daughter cells which differentiate into plasma or memory cells
plasma cells produce antibodies
memory cells remain in blood until antigen returns and then they divide rapidly into plasma cells

Question 9

What is the primary response?

Answer 9

when the antigen first enters the body

slow acting and involves B lymphocytes and T lymphocytes

Question 10

What is the secondary response?

Answer 10

when the antigen enters the body for a second time, memory cells (specific to one antigen) divide to form plasma cells which produce antibodies
antibodies here are produced faster and in greater quantities

Question 11

How can someone get ill from the same illness multiple times?

Answer 11

some diseases have a number of different antigens so there is more than one memory cell needed for each antigen

Question 12

What is active immunity?

Answer 12

when a person is exposed to an antigen and the immune response occurs and they produce their own memory cells

• takes time to develop
• long lasting

Question 13

What is passive immunity?

Answer 13

antibodies are injected into a person so they do not have their own immune response or make their own memory cells

• fast acting
• short lasting

Question 14

What is a vaccine?

Answer 14

dead or weakened pathogen or antigen

a form of artificial immunity

Question 15

How do vaccines work?

Answer 15

specific T lymphocytes detect antigen
release cytokines to activate specific B lymphocytes
B lymphocyte receptor bind to specific antigen
B lymphocytes divide to form clones- plasma /memory
plasma cells produce antibodies
memory cells stay in blood and produce antibodies faster in secondary response

Question 16

What are monclonal antibodies?

Answer 16

antibodies which are specific to an antigen as they have a specific binding site due to a unique tertiary structure

Question 17

What is an antibody?

Answer 17

protein with a specific binding site produced by plasma cells that form antigen- antibody complexes

Question 18

What is the structure of an antibody?

Answer 18

made up of four polypeptide chains
2 heavy chains and 2 light chains

variable region has specific amino acid sequence
the shape / tertiary structure of the binding site is complementary bind with antigens
forms antigen- antibody complex

Question 19

ELISA test precautions

Answer 19

enzyme linked immunosorbent assay
wash in between to remove unbound antibodies/antigens to avoid false positive
there are control wells; to ensure nothing else is causing the colour change
to ensure the washing steps have been thorough
children receive antibodies from their parents so a positive test could show up

Question 20

What is the test for an antigen?

Answer 20

apply monoclonal antibody specific to an antigen
wash
apply body fluid suspected of containing antigen
wash
apply monoclonal antibody attached to an enzyme
wash
add substrate- enzyme causes a colour change

Question 21

What is the test for an antibody eg HIV?

Answer 21

HIV antigen is added
body fluid is added to the well (HIV antibodies will bind to HIV antigen)
wash
monoclonal antibody with enzyme is added (will bind to HIV antigen)
wash
substrate is added and will change colour if HIV antibodies are- if person is HIV positive

Question 22

Why do antibodies have 2 binding sites?

Answer 22

so they can bind to more than one pathogen which clumps them together (agglutination) which reduces chances of pathogens spreading and attracts phagocytes to engulf lots of pathogen at one time