Immunology 3-4 Flashcards
What are our anatomical barriers to infection?
- Skin (mechanical barrier and acidic environment)
- Mucous membranes (trap microorganisms and expel using cilia)
What are the physiological barriers to infection?
- Body temperature
- pH (stomach acid kills some ingested microorganisms)
- Chemical mediators (interferons, complement, lysozyme)
- Phagocytic cells
What does a neutrophil do?
Can perform phagocytosis and is often one of the first cells to the site of infection.
What percentage do neutrophils make up of all WBCs?
40-70%
What do macrophages do?
Phagocytosis and cytokine release. Less abundant that neutrophils but still widely dispersed.
What do eosinophils do?
Phagocytosis, granule release and defence against parasitic infections.
What do basophils do?
Granule release and can sometimes be an APC. Main source of histamine.
What does a mast cell do?
Pro-inflammatory granule release causing vasodilation and increased vascular permeability.
What does a dendritic cell do?
Antigen capture in the epidermal layers, migrates to the lymph nodes and presentation to T lymphocytes. Can also secrete cytokines.
What does a NK cell do?
Lyse infected cells by large granules of interferon-gamma.
What is opsonisation?
Coating of a pathogen with proteins to facilitate phagocytosis. Opsonins binds to antigens.
What are cytokines?
Small secreted proteins that are in charge of cell-cell communication and are thought of as the messengers of the immune system. They act locally and have a short half-life but can be biologically active at very low concentrations.
Give some examples of cytokines.
- Interferons
- Interleukins (between lymphocytes)
- Chemokines
- Growth factors
Where are the complement components produced?
Liver
What is the complement system?
It enhances the activity of specific antibodies in lysing bacteria, amplifying response to immunological stimuli.
How is the complement system activated?
C-reactive proteins and Mannan binding proteins.
What are the four functions of the complement system?
1) Opsonisation
2) Lysis
3) Activation of inflammatory response
4) Clearance
What type of cell produce antibodies and what are they?
Plasma cells. A protein that is produced in response to an antigen and has the property of binding to that specific antigen.
What is the Fc region?
The constant, crystallising region. It is able to crystallise due to regular sequence of proteins.
What is the Fab region?
The hyper variable region of the antibody which binds to the antigen?
What is the variable region made up of?
Three separate hyper variable regions called ht complementarily determining regions (CDRs).
What are the two main sections of an antibody?
Fc and Fab
What does the hinge region allow?
Allows antibodies to bind at different spacings.
What holds the heavy and light chains together?
Disulphide bridges.
Explain the nature of the interactions between the antigen and the antibody.
Individually weak as they are covalent however they are several interactions which compensate for the individual weakness.
What is antibody affinity?
Strength of total non-covalent interactions between single antigen binding site and a single epitope.
What is antibody avidity?
Overall strength of interactions between antibody and antigen.
What are the five classes of immunoglobin?
IgA, IgD, IgE, IgG and IgM.
What light chains do they have?
All Kappa or Lamda.
What heavy chains do they have?
A- Alpha D- Delta E- Epsilon G- Gamma M- Mu
What are the further subclasses of IgA and IgG?
IgA - IgA1 and IgA2
IgG - Ig1, Ig2, Ig3, and Ig4
Which is the most abundant immunoglobin?
IgG
Where is IgA present and what does it protect against?
Mucosal surfaces (monomer in blood but dimer in secretions). Protects against bacteria, viruses and protozoa.
Where is IgD expressed?
On the surface of B cells - involved in cell development and activation. Very low concentrations.
What is IgE involved in?
Allergic reactions and parasitic infections by binding to FCeRI receptors on the surface of mast cells causing histamine release.
Where is IgG present?
Transported across the placenta to unborn foetus so involved in passive immunity. Found in blood, tissues and ECM also.
Where is IgM found?
Mainly the blood due to its large size (pentameric structure with 10 binding sites).
Which two immunoglobin classes are involved in activating the complement system?
IgG and IgM
Which immunoglobin class is first formed after initial infection?
IgM
