Lecture 2 Flashcards
What are the three key functions of antibodies?
Neutralisation of toxins or viruses
Opsonisation (primes particles or microbes for phagocytosis or destruction by Fc-R bearing cells)
Complement activation (which leads to lysis of pathogen)
What part of the antibody molecule is different to give different isotypes?
the CH domain
What are the 5 main antibody isotypes?
think Madonna - MADGE
IgM IgA IgD IgG IgE
What are the two components of an antibody’s antigen binding site?
VH (variable section of heavy chain)
VL (variable section of liht chain)
Which antibody isotype is the RESTING B cell receptor?
IgM
What is the name for an activated B cell?
Plasma cell
Which other cell type is involved in B cell activation (most of the time)?
Helper T cell (CD4 positive)
Name five cells other than B cells which have Fc receptors.
Macrophage Eosinophil Neutrophil NK cell Mast cell
Which antibody type is most important in complement fixation and agglutination?
IgM
Which antibody isotype is pentameric?
IgM
Which antibody isotype is responsible for OPSONISATION of antigen for phagocytic cells?
IgG
What is the type of receptor expressed by phagocytic cells which enable them to phagocytose IgG-coated antigen?
Fc-gamma receptor
Which antibody isotype is found in mucosal secretions such as milk and tears? Why is this?
IgA - because IgA2 is able to cross mucosal barriers.
What is the main role for IgA?
Neutralisation of foreign toxins or viral particles found in mucosal secretions and blood
Which cell types express Fc-epsilon receptor?
Mast cells and basophils
What is the role of IgE?
When cognate antigen binds two neighbouring IgE molecules that are bound to a mast cell via the Fc-e receptor, cross linking of the two IgE’s creates a signal that leads to mast cell degranulation.
What sort of placenta do primates have? Which isotype can cross?
Haemochorial - IgG
What sort of placenta do dogs and cats have? Which isotype can cross?
Endotheliochorial - IgG (only 5-10%)
What sort of placenta do ruminants have? Which isotype can cross?
Syndesmochorial - none
What sort of placenta do horses and pigs have? Which isotype can cross?
Epitheliochorial - none
What is an example of passive immunisation in veterinary medicine?
Administration of anti-toxin to a tetanus or snake bite patient
Which of the three mechanisms of antibody action is performed by anti-toxins?
Neutralisation
How are anti-toxins commercially available?
IgG is ‘grown’ in and ‘harvested’ from healthy horses by immunising them with toxoid molecules (chemically inactive version of the toxin).
What are the five characteristics of a secondary adaptive response? (second time exposure to antigen)
- Faster reaction time
- Higher antibody titres generated
- Different isotype proportions (more IgG second time, less IgM)
- T cell help required (check this)
- Antibodies are of higher affinity to the antige
