Immune system 2 Flashcards
What are interferons?
Cytokines that inhibit viral replication within cells
Describe how interferons are activated and their effects
Activated macrophages release IL-12 which stimulates IFNgamma by natural killer cells and lymphocytes
IFNgamma leads to further macrophages activation in feedback loop amplifying innate immune response
Increases phagocytosis and iNOS expression
Which cytokines induce endothelial cells to express adhesion molecules allowing neutrophils and monocytes to bind and leave the blood stream
IL-1
TNFAlpha
What is the role of IL-8?
Potent neutrophil chemoattractant and activates macrophages
What 3 things act on the endothelium to increase permeability?
TNFAlpha
Platelet Activating Factor
PG
PAF causes what in relation to platelets?
Causes platelets to release histamine also increases vascular endothelial permeability
Define complement
A group of plasma and cell membrane proteins that leads to the formation of a membrane attack complex and inflammation
What is the role of complements?
Directly recognises pathogen, insert into membrane results in membrane attack eg holes in the surface
think cell lysis
Which cell is part of the humoural response?
B-cell
Which cells are part of the cellular immune response
CD4+ T cell
CD8+ T cell
Where are T lymphocytes derived from?
Thymus
Where are B lymphocytes derived from?
Bursa of Fabricus in mammals the bone marrow
What do B lymphocytes produce?
AB antibodies known as immunoglobins
Describe the humoral response
B cells have B cell receptor, a surface bound antibody
Antibodies are opsonins that bind proteins,sugars and rarely lipids
Facilitate uptake of AG as Ab-Ag complex binds Fc receptors on phagocytic cells
Describe the structure of an antibody
Y shaped 2 heavy chains - 50-75kDa 2 light chains-25kDa Chains linked by disulphide bonds Hinge region Fab and Fc portions
What is the role of the hinge region on an antibody?
What is it made out of?
Gives the molecule flexibility
Made from prolines breaking the alpha heliex
What did antibodies evolve from?
Primordial gene encoding a polypeptide of about 110 amino acids
What part of the antibody gives specificity?
N terminal of the Fab portion
Which region of an antibody is constant?
The Fc domain
What does an antibody bind to?
The epitope- part of an antigen
How many amino acids long are epitopes?
8 to 22
Define affinity in relation to the antibody-antigen binding
The strength of the interaction between an antibody and antigen
Define avidity
The binding of a whole antibody
Name the 2 types of antibodies
Monoclonal antibody
Polyclonal antibody
Where so monoclonal antibodies come from?
And how many epitopes does it have?
Comes from a single B cell and has a single epitope
Where so polyclonal antibodies come from?
And how many epitopes does it have?
Produced by the different B cells and recognises different epitopes
Name 3 uses of antibodies in biotechnology
Detection of neutralising antibodies in a patient
Detection of antigens in a virus or a cell
Therapeutics- monoclonal only
How many classes of antibody are there?
5
Name the 5 Ab classes of antibody.
How are these determined?
IgM IgG IgA IgE IgD
Determined by the structure of the Fc domain
Which antibody class is the most abundant?
IgG
Accounts for 70%
The specificity is not related to its class
What does this mean?
Different classes of antibody raised to a target have the same specificity
What are the 6 roles of antibodies?
Neutralisation Agglutination Opsonisation Complement Activation Trigger mast cell degranulation Activate B lymphocytes
Describe how antibodies cause neutralisation
Ab binds to toxins released by the bacteria
Ab can block viral binding proteins
Block the adherence of bacteria to host cells
What is opsonisation?
When a pathogen is marked for phagocytosis
Describe how a B cell is activated and what it produces
Naive B cell is actiavted and divides into memory cells or plasma cells
What is the difference between Memory cells and plasma/effector cells?
Memory cells have a long life span and have the same BCR as parent cells
Plasma cells lived a few days but secrete antibodies
Describe clonal expansion/ clonal selection
Antigen binding the particular B cell bound antibody molecules inniates clonal expansion
Produced large number of specific B cells
Antibodies of higher affinity evolve selecting B cells expressing antibodies with high affinity
Which antibody is first secreted in clonal selection?
IgM then later class switching
What are the roles of the CD4+ T cells?
Immunity against intracellular bacteria and parasites
Provide help to CD8 Tcells
Promotes humoural immune response
What are the roles of the CD8+ T cells?
Cytotoxic when activated
Kill virally infected cells
Kill tumour cells
Where do all blood borne immune cells originate from?
Hematopoietic stem cells
What is haematopoiesis?
formation of blood cells
Where does haematopoiesis occur in the 3rd to 7th month of gesteration?
Fetal liver then spleen
