immune system

Question 1

antigen

Answer 1

• molecules (usually proteins or polysaccharides) found of surface of cell
• when pathogen invades body, antigens on cell surface identified as foreign, activates cells in the immune resposne

Question 2

non-speicifc and specific resposne

Answer 2

• non-specific
  
  • happens in same way for all microorganisms
• specifc
  
  • aimed at specific pathogen
  • involves T and B lymphocytes

Question 3

phagocytosis

Answer 3

• engulfment of pathogen
• non-sepcifc
• phagocyte recognises antigens
• cytoplasm of phagoccyte moves round pathogen , engulfing it
• made easier by the presnecen of oposonins
• pathogne then containing in phagogosome (type of vesicle) in the cyotoplasm
• a lysosome fuses with the phagosome
• enzymes released break down pathogen
• phagocyte presents pathogens antigens on surface to activate other immune system cells
  
  • antigen presenting cell

Question 4

opsonins

Answer 4

• molecules in blood that attach to attach to foreign antibodies to aid phagocytosis
• some hide the -ve charges on the membrane, making it easier for -vely charged phagocyte to get closer to the pathogen

Question 5

neutrophils

Answer 5

• type of phagocyte
• first WBC to respond
• move toward wound and release cytokines

Question 6

phagocytes stimulat T lymphoscyte

Answer 6

• type of WBC
• surface covered with recepetors
• bind to antigen presented by APCs
• each has different receptor on its surface
• when the receptor on the surface meets a complimentary antigen it binds to it
  
  • so each T lymphocyte iwll bind to a different antigen
• this activates the T lymphocyte
  
  • clonal selection

Question 7

clonal expansion

Answer 7

• T lymphocyte divides to produce clones
• different T lymphocytes perform different functions

Question 8

Types of T lymphocyte

Answer 8

• T-helper
  
  • release susbtances to activate B lymphocytea and T killer cells
• T killer cells
  
  • attack to and kill cells that are infected with a virus
• T regulatory cells
  
  • suppress immune resonse from other wbc
  • stops the immune system mistakenly attacking the host’s body cells

Question 9

B lymphotcytes

Answer 9

• another type of WBC cells
• covered w/ antigbodies
  
  • bind to antigens to from and antigen-antibody coplex
• each B lymphocyte has different shaped antibody on its surface
• when the antibody on the surface meets a complementary shaped antigen, it binds to it
• together with substances released from T helper cells, acitvates the B lympocytes
  
  • clonal selectron
• activated B lymphocytes divides by mitosis into plasma cells and memory cells
  
  • clonal expansion

Question 10

Plasma cells

Answer 10

• make more antibodies to a specific antigen
• clones of the B lymphocyte
• secrete loads of the antibody, specific to the entigen, into the blood
• form lots of antigen-antibody complexes

Question 11

structure of antibodies

Answer 11

• variable regions
  
  • form antigen binding sites
  • shape is complementary to an antigen
  • variable regions differ between antibodies
• hinge region allows flexibility when the antibody binds to the antigen
• constant region allow binding to receptors on immune system cells
• disulfide brides hold the polypetide chains together

Question 12

how do antibodies work

Answer 12

• agglutinating pathogen
  
  • two binding sites, bind to two pathogen at the same time, clumping them together
  • phagoctes then bind to antibodies and phagocytose a lot of pathogen all at once
• neutralising toxins
  
  • antibodies called anti-toxins bind to toxing
  • prevents them form affecting human cells
  • inactivated
• preventing the pathogen binding to humans cells
  
  • antibodies blod the cell surface receptors that the pathogen needs to bind to hose cells
  • cant attach or infect the hot cells

Question 13

How is the primary response slow

Answer 13

• antigens activate immune system when a pathogen first enters body
• aren’t many B lympohcytes that can make the antibody needed to bind to it
• evenutally the body will produce it enough

Question 14

immunity

Answer 14

• aftrer being exposed to antigen, T and B lymphocytes produce memory cewlls, remain in blood for along time
• memory T lymphocytes
  
  • remember the specific antigen and recognise it second time
  • record specific antbodies
• symptoms still shown

Question 15

secondary respoisne

Answer 15

• • • if same pathogen enter body, response will be quick and stronger
• clonal selection happens faster
  
  • memory B lympohocytes are activated and divide into plasma cells that produce the right antibody
  • divide into the correct type of T lympohscyte
• often gets rid before u show sympton

Question 16

blood smear

Answer 16