1.1 Pre Course Tutorisls Part 2 Flashcards
What are antibodies (immunoglobulins)
Proteins produced by plasma cells. Used by the immune system to neutralise pathogens
Can be found in two forms: a soluble form secreted by plasma cells or in a fixed membrane bound form attached to the surface of a B cell.
How to antibodies fight antigens?
They recognise a key fragment of a pathogen and bind to it via the fragment antigen binding variable region (FAB)
What are the 5 different antibodies that exist in humans?
IgA- present within secretions such as tears and breast milk
IgD-
IgE- form part of the response to parasites and allergic reactions
IgG- form secondary antibody response, cross placenta
IgM- largest antibodies, form primary antibody response. Due to their size they are much more effective at activating compliment
What are the four ways antibodies are involved in antigen neutralisation?
Bind to antigens directly to form immune complexes which are cleared through the liver and spleen
Act as poisonings for phagocytoisss
Activate the complement cascade through the classical pathway
Bind to their cells and initiate a non-phagocytic cell mediated destruction of the cells called antibody dependent cellular cytotoxicity.
What is antibody mediated cellular toxicity?
A way that specific antibodies can initiate the killing of pathogens or target cells via immune cells from the innate immune system.
Circulating antibodies bind to complementary antigen receptors on the target cell via the fab region. The FC (bottom) end of the antibody can bind to a number of immune cells
What immune cells can the FC bind to?
NK cells
Macrophages
Neutrophils
Eosinophils
What is antibody dependent cellular toxicity.
It’s activates several phagocytic cells. However the destruction of the problematic cell does not involve phagocytosis.
How does antibody dependent cellular cytotoxicity work?
Activates NK cells and destroys problematic cells through the release of perforin and granzyme
What else can be activated when bringing to the FC portion of an antibody?
Macrophages neutrophils and eosinophils which cause the release of granules and toxic enzymes to facilitate extracellular destruction of the target cell
What is the purpose of B lymphocyte production?
Production and release of antibodies
Occurs mainly in the spleen and lymph nodes.
What cell surface receptor is found on all B cells
a B cell receptor, essentially an antibody
What ensures a great complexity in binding of antigens?
VDJ recombination allows for a great diversity in the number of the potential of antigen binding sites
What are the three mechanisms that B cells are activated in secondary lymph organs?
T cell dependant activation- B cells are activated by T cells
T cell independent activation- B cells are activated by antigens typically lipids or polysaccharides
Specific to memory B cells, when it encounters a specific antigen it differentiates into plasma cells which results in a release of antigen specific antibodies
What happens after a B cell is activated?
If bound to an antigen can turn into a short lived plasma cell releasing IgG and IgM
Can enter the germinal centre or a lymph node in order to proliferate, develop an ability to bind to the antigen or undergo immunoglobulin class switching
What is immunological class switching
Refers to the process by which B cells become able to produce a different class of immunoglobulin that can respond to the same antigen. Once these events have occurred the B cell can travel out the lymph node back to the bone marrow where it can become a memory B cell or a long lived a B cell.
What happens the first time a foreign antigen is encountered?
A lag phase occurs while B cells differentiate into plasma cells. During the lag phase no antibodies are produced. Once plasma cells have formed a low volume of IgM antibodies are released to neutralise this initial infection. IgG are memory B cells are a,so released.
What happens if a foreign antigen is encountered again?
There is an accelerated reaction initiated by memory B cells which immediate,y recognise this antigen. Once activated memory B cells quickly proliferate and create plasma cells causing a quick release of high volume IgG antibodies
What is the innate immune system?
A fats non specific initial response to pathogens. If the pathogens are able to overcome the natural barriers that keep infection at bay, these are the next step in dealing with them
What cells are involved in the innate immune system?
Mast cells Basophils Neutrophils Eosinophils Monocytes (macrophages and dendritic cells) Natural killer cells
What are the functions of the innate immune system?
Antigen recognition Inflammation Recruitment of immune cells NK cytotoxicity Phagocytosis and endocytosis Opsonisation Activation of complement cascade
What are pattern recognition receptors?
Receptors that are located on the cell surface membrane. They distinguish certain cellular motifs that are common amongst most groups of different pathogens. Often these molecular motifs are essential to the pathogens survival
What happens after pathogens are recognised the skin?
Macrophages release pro inflammatory cytokines including interleukin 1, tumour necrosing factor alpha are released by these macrophages.
What occurs during the inflammatory process?
Vascular permeability is increased
Other immune cells are recruited
Seals off invading pathogen
Adhesions molecules are activated to allow leukocytes to adhere to the endothelium
Chemokines are released to recruit immune cells to the point of inflammation
How do neutrophils adhere to the epithelium?
They bind onto selectin which provides friction and allows the molecules to roll to a stop
