Block D Lecture 1: Humoral and Antibody Mediated Immunity Flashcards
What are the 2 times of acquired (specific) immunity?
Cell-mediated Immunity
Antibody-mediated immunity
(Slide 3)
What 2 factors decides what response the immune system takes against a pathogen?
Its size
Whether it’s extra or intracellular
(Slide 4)
What are the 4 steps of the humoral activation phase?
Phagocytosis of pathogen by Antigen presenting cells (APCs)
Antigen processing / presentation
Education of naïve T cell
Clonal expansion of T cell
(Slide 5)
What are the 4 steps of the humoral effector phase?
Uptake of pathogen by B cell
Antigen processing / presentation
Interaction with antigen specific T-cell
Clonal expansion of B cells and differentiation to plasma cell
(Slide 6)
What 5 antigens can antibodies recognise?
Proteins
Carbohydrates
Nucleic acids
Glycolipids
Small inorganic molecules
(Slide 7)
How many identical light and heavy chains do antibodies have?
2 of each
(Slide 8)
What chain of the antibody determines the isotype class of antibody (E.g. IgA, IgD, IgE.. etc)?
The heavy chain
(Slide 8)
What makes up the antigen binding regions in an antibody?
The variable regions of both the light and heavy chains
(Slide 8)
How many antigen binding regions does an antibody have?
2
(Slide 8)
What does the Fc portion (the heavy chain constant regions) bind to?
A cell surface receptor
(Slide 8)
What 4 places is IgA antibody found?
Breastmilk
Lung and airways
Intestinal lumen
Urogenital tract
(Slide 11)
Where is IgE antibody found?
Connective tissue mast cells
(Slide 11)
What 3 places is IgG antibody found?
Blood
Maternal blood (to supply a foetus)
Extravascular tissues
(Slide 11)
Where is IgM antibody found?
Blood
(Slide 11)
What form of IgA can survive on mucosal surfaces?
The dimeric form
(Slide 12)
What is the most common type of primary antibody deficiency?
Selective IgA deficiency
(Slide 12)
Why can an IgA deficiency appear asymptomatic?
As IgM can compensate
(Slide 12)
What 2 pathogens is IgA important in defending against?
Intestinal pathogens
Virus particles
(Slide 12)
What is the main antibody in the secondary response?
IgG
(Slide 14)
What does IgG provide to a baby?
Neonatal protection until the baby’s immune system develops
(Slide 14)
How does IgG provide neonatal protection to a baby?
By crossing the placenta and into the Fetal bloodstream
(Slide 14)
Roughly what percentage of circulating immunoglobulins in the blood are IgG?
75%
(Slide 14)
What 4 things does IgG mediate in?
Phagocytosis
Opsonisation
Antibody-dependent cellular cytotoxicity by NK cells
Degranulation of neutrophils, eosinophils and mast cells
(Slide 14)
Where is IgD inserted?
Into the B cell membrane
(Slide 16)
What does IgD act as after inserted into the B cell membrane?
The B cell receptor for antigens
(Slide 16)
What is the half-life of IgD?
3 days
(Slide 16)
What 2 pathogens is IgD thought to be protective against?
Mucosal and respiratory
(Slide 16)
What antibody is the first antibody secreted in the primary response?
IgM
(Slide 17)
What is natural IgM?
IgM which is present in babies
(Slide 17)
What is adaptive IgM?
IgM produced in response to antigenic stimulation of B cells
(Slide 17)
What 2 types of microbial components can IgM recognise?
Viral antigens and bacterial toxins
(Slide 17)
What does the high avidity of polymeric IgM mean?
It can immobilise a target at a site
(Slide 17)
What is IgE meant to protect against?
Worm infestations
(Slide 19)
What is IgE associated with in 1st world countries?
Type 1 allergic reactions
(Slide 19)
How is IgE mediated?
Through degranulation of granulocytes
(Slide 19)
How does IgE release pre-formed mediators?
IgE-mediated activation occurs through FcεRI on mast cells and basophils/multivalent (having multiple sites to attach to an antibody) antigens cross-link the receptor-bound IgE to trigger degranulation and the release of pre-formed mediators
(Slide 19)
What do the pre-formed mediators release by IgE result in?
Allergic reactions
(Slide 19)
What does the pro-inflammatory response triggered by IgE induce?
A T helper 2 (Th2) immune response
(Slide 19)
Where do specific IgE bound to mast cells recognise antigens?
In venom from stings / bites
(Slide 19)
How can IgE activation inactivate venom from stings / bites?
By causing mast cell degranulation and release of enzymes which inactivate the venom
(Slide 19)
What are the 6 antibody mediated effector functions?
Neutralisation
Agglutination (clump together antibody and pathogen)
Opsonisation
Activation of complement cascade
Antibody-dependent cell mediated cytotoxicity (ADCC)
Trigger degranulation of granulocytes
(Slide 21)
Why are T-independent (T-cell independent) responses fast?
Because B cells are directly activated by antigens with certain types of structure
(Slide 23)
Why is IgM the only class of antibody that can be produced in T-independent response?
As T cells are needed to help B cells class switch
(Slide 23)
What is the disadvantage of T-independent response?
Short life-span and are therefore not protective
(Slide 23)
Does T-independent response make memory cells?
No
(Slide 23)
What are T-dependent (TD) antigens?
Antigens that require the involvement of T cells to start a strong immune response
(Slide 24)
What 6 functions requires T lymphocyte (T cells) to B lymphocytes (B cells)?
B cell proliferation
Production of immunoglobulins
Immunoglobulin class switching
Rescue of B cells from apoptotic death
Germinal centre formation
Generation of B lymphocyte memory (Memory B cells)
(Slide 24)
What 2 classes can T-independent (TI) antigens be divided into?
TI-1 (TI type 1)
TI-2 (TI type 2)
(Slide 25)
What are TI type 1 (TI-1) antigens?
Polyclonal (derived from many clones) B cell activators
(Slide 25)
What are TI type 2 (TI-2) antigens?
Antigens able to directly stimulate B cells
(Slide 25)
What antibody is specialised to activate complement efficiently upon binding an antigen?
IgM
(Slide 28)
What are the primary and secondary immune responses?
The primary immune response is the first time the immune system encounters an antigen and the secondary immune response is any subsequent times it encounters the antigen
(Slide 30)
How do memory cells make the secondary immune response faster?
As they remember each antigen encountered
(Slide 30)
