Antibody, Lymphocytes & Generation of Diversity (#2) Flashcards
List the general functions of antibodies
- neutralise toxins + viruses
- opsonise pathogens
- activate complement cascade to kill pathogens
- agglutinates particles
How do antibodies neutralise toxins + viruses?
- binds to them + blocks interactions with other cells
- as it stops toxins/virus binding to its receptor to prevent entry into target cell
How do antibodies opsonise pathogens?
- binds to them to promote phagocytosis + killing activity by other cells by recognition of Fc receptors on macrophages
How do antibodies agglutinate pathogen debris, viruses etc?
- antibody has more than 1 binding site so can cross-link antigens together + disarm them by making them into complex
What is important about IgG in serum?
- main serum antibody
- gen measurement of antibody titre in serum in response to vaccine
What is IgG good at?
- opsonisation (coating pathogens so phagocytic cells can recognise them)
- many cells have Fc receptors for IgG
What happens to pathogens coated in IgG?
- targets for killing by NK cells = antibody-dep cellular cytotoxicity - also depends on Fc receptors
List the subclasses of IgG and how are they named?
- IgG1, IgG2, IgG3, IgG4
- most (IgG1) to least abdundant (IgG4) in serum
How is IgA found in serum?
as a monomer
How is an IgA dimer formed?
2 monomers joined by joining J chain
Describe how dimeric IgA is used in the gut lumen?
1) plasma cells secrete IgA
2) IgA binds to receptor (secretory component)
3) IgA then transported into gut lumen
4) IgA can bind + agglut intestinal bacteria + regulate pops
What is dimeric IgA good at + why?
- agglut + neutralising bacteria bc it has 4 binding sites
How does IgA retain antigen to mucus?
- charge CHO rich SC of secreted IgA can bind to mucus
- can retain antigens on mucus surface to prevent them from causing damage
What is special about IgM?
- 1st antibody made in immune responses + so 1st one prod in vaccination
Why is the structure of IgM important?
- pentamer so has 10 poss binding sites
- has high avidity (ability of whole mol to bind rather than 1 particular binding site)
- agglut v. effective as it can form lattice + also good fixer of complement
What receptors do mast cells have and the consequence of this?
- Fc receptors for IgE
- can bind in absence of allergen
What is conc of IgE in indiv with allergies?
higher conc in serum
What happens when you breathe in pollen?
- pollen binds + can cross-link IgE on surface of mast cell
- causes mast cell degranulation
What causes the symptoms of pollen allergy?
- granules released by mast cells
Which antibodies are expressed on surface of newly formed B cells?
- IgM + IgD with same specificity
How much IgD is found in serum?
v. little
Which cells can improve their specificity for antigen + how?
only B cells by affinity maturation
Why do lymphocytes constantly recirc through blood + lymphoid tissues?
inc probab of encountering antigen they can bind to
What do secondary lymphoid tissues contain?
- zones of div B cells = germinal centres
