4.1.7 antibodies Flashcards
agglutins
antibodies that cause pathogens to stick together
anti-toxins
antibodies that render toxins harmless
opsonins
antibodies that make it easier for phagocytes to engulf the pathogen
primary immune response
initial response caused by 1st infection
secondary immune response
more rapid & vigorous response caused by 2nd or subsequent infection caused by same pathogen
what are antigens
a molecule that can stimulate an immune response
what molecules are usually antigens
(almost any molecule could be an antigen)
they’re usually proteins/glycoproteins in plasma membrane of pathogen
what are antibodies specific to
the antigen
antibodies are..
immunoglobins
what are immunoglobins
complex proteins produced by plasma cells in the immune system
when are immunoglobins released
in response to an infection
structure of an antibody
- 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
3 main groups of antibodies
- opsonins
- agglutins
3 anti-toxins
how do opsonins work & what are they
- 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
what’s neutralisation
- 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
how do agglutins work & what are the 2 advantages
- 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
how do anti-toxins work
some antibodies bind to molecules that are released by pathogenic cells
–> these molecules may be toxic & anti-toxins render them harmless
what’s the primary immune response (graph)
- immune system produces antibodies once infecting agent is detected
- few days before number of antibodies in blood rises to level that’s able to combat infection effectively
what’s the secondary immune response (graph)
- antibodies don’t stay in blood
however, if body is re-infected:
- B/T memory cells circulating in blood
- recognise specific antigens & immune system can start quicker
- production of antibodies starts sooner/is more rapid
- concentration of antibodies rises sooner & reaches higher concentration
