Acquired Flashcards
Immunoglobulins (antibodies) are a characteristic Y shape What is the role of the tip of the Y shape, and the end of the Y shape?
The antigen binding site (the two tips of the Y) - highly variable and binds to the antigen on a foreign body.
Constant region (end of Y) can bind to receptors on the cell surface.
What are the 5 different immunoglobulin classes and their functions?
IgG - Opsonisation, activates complement.
IgA - Mucosal defence .
IgM - Agglutination (clumping) of pathogens.
IgE - Defence against helminths.
IgD - Lymphocyte maturation.
Will a complex antigen or a carbohydrate/repetitive antigen be easier to recognise by an antibody?
Complex is easier, Carbohydrate/reptitive is harder to recognise.
Three types of Antigen presenting cells?
Macrophages - Widely distributed.
Langerhan’s cells - found in the skin.
Kupffer cell - found in the liver.
How is MHC II involved in the presentation of antigens?
After the Pathogen is broken down, MHC II picks up a fragment of the antigen in the phagosome, and then MHC II and the fragment are presented on the cell surface.
Where do T cells mature? and where produced?
Mature in the thymus, produced in the bone marrow.
Three cells that T-cells mature into, and how?
T-helper cells - via TCR (T cell receptor) activation involving CD4 +ve activation by APC’s (antigen presenting cells)
Cytotoxic T-cells - via TCR (T cell receptor) activation involving CD8 +ve activation which recognise ‘altered self’.
Natural Killer cells.
How do CD4 +ve cells differentiate into a T-helper cell?
The TCR (T cell receptor) interacts with the antigen fragment, Causing the release of IL-2 (interleukin - 2) causing cells to differentiate into T-Helper cells.
How are B-cells activated?
B-cells have different Ig’s on their cell surface, the interaction of an antigen with one type of Ig stimulates the proliferation of this B-cell, the B-cell can also then be stimulated by an ‘armed’ T-helper cell this causes the proliferation into a plasma cell and the production of the Ig that was originally presented on it’s surface.
What happens during a Plasma cell class switch and how is this accomplished?
The constant region of an IgM can be switched to IgG or IgA or IgE. the antigen binding site remains unchanged.
Through T - helper cell cytokines.
Summarise the actions of cytotoxic T cells.
Recognise MHC I plus a viral peptide to recognise virally infected cell, the T killer cell then releases perforin causing perforations in the cell membrane and killing the cell.
How are antibodies produced by the B-cell?
Heavy chain (with constant µ region is produced) the antigen binding site is coded for by the VDJ and the constant region is coded for by Cµ.
After the heavy chain is produced the cell goes on the produce a light chain with either a K or Gamma (Y) constant region.the antigen binding site is coded for by VJ this time.
Five ways in which Antibodies help fight infection?
Exclusion.
Phagocytosis.
Activation of Complement.
Activation of mast cells.
Activation of eosinophils.
What is exclusion?
When antibodies cause Agglutination preventing the pathogen from entering the body.
How does secretory IgA, and IgM contribute to exclusion?
IgA forms a dimer with 4 antigen binding sites and binds to pathogens.
IgM forms a pentamer with ten antigen binding sites which bind to pathogens and prevent them gaining access to the bodies cells.
