4.1.7 antibodies

Question 1

agglutins

Answer 1

antibodies that cause pathogens to stick together

Question 2

anti-toxins

Answer 2

antibodies that render toxins harmless

Question 3

opsonins

Answer 3

antibodies that make it easier for phagocytes to engulf the pathogen

Question 4

primary immune response

Answer 4

initial response caused by 1st infection

Question 5

secondary immune response

Answer 5

more rapid & vigorous response caused by 2nd or subsequent infection caused by same pathogen

Question 6

what are antigens

Answer 6

a molecule that can stimulate an immune response

Question 7

what molecules are usually antigens

Answer 7

(almost any molecule could be an antigen)
they’re usually proteins/glycoproteins in plasma membrane of pathogen

Question 8

what are antibodies specific to

Answer 8

the antigen

Question 9

antibodies are..

Answer 9

immunoglobins

Question 10

what are immunoglobins

Answer 10

complex proteins produced by plasma cells in the immune system

Question 11

when are immunoglobins released

Answer 11

in response to an infection

Question 12

structure of an antibody

Answer 12

• y-shaped
• 4 polypeptide chains
• disulfide bridges hold polypeptides together
• hinge region = allow flexibility to allow molecule to grip 1+ antigen
• 2 distinct regions:
  1. variable region = shape specific to antigen
  2. constant region = same in all antibodies –> may have site for easy binding of phagocytic cells

Question 13

3 main groups of antibodies

Answer 13

1. opsonins
2. agglutins
   3 anti-toxins

Question 14

how do opsonins work & what are they

Answer 14

• group of antibodies which bind to the antigens on a pathogen
• then act as binding sites for phagocytic cells
• some aren’t very specific & stick to types of molecules that are not found in the host cell
• others are produced as part of the specific immune response & bind to very specific antigens
• assists in phagocytosis but prevents the pathogen entering a host cell before it can be attacked by phagocytes

Question 15

what’s neutralisation

Answer 15

• the pathogen may have another use for the antigen molecule
• eg. it may be a binding site used for attachment to the host cell
• the opsonin bound to the antigen renders it useless
  = neutralisation

Question 16

how do agglutins work & what are the 2 advantages

Answer 16

• as each antibody molecule has 2 identical binding sites, it is able to ‘cross-link’ pathogens by binding an antigen on 1 pathogen with 1 binding site & then an antigen from another pathogen with its other binding site
• when many antibodies perform this cross-linking they clump together (agglutinate) pathogens
• particularly effective against viruses

2 advantages
- agglutinated pathogens are physically impeded form carrying out some functions eg. entering host cells
- agglutinated pathogens are readily engulfed by phagocytes

Question 17

how do anti-toxins work

Answer 17

some antibodies bind to molecules that are released by pathogenic cells
–> these molecules may be toxic & anti-toxins render them harmless

Question 18

what’s the primary immune response

Answer 18

• immune system produces antibodies once infecting agent is detected
• few days before no. of antibodies in blood rises to level that’s able to combat infection effectively

Question 19

what’s the secondary immune response

Answer 19

• antibodies don’t stay in blood

however, if body is re-infected:
- B/T memory cells circulating in blood due to specific immune response
- recognise specific antigens & immune system can start quicker
- production of antibodies starts sooner/is more rapid
- conc. of antibodies rises sooner & reaches higher conc.