Immune System 2 Flashcards
What does TLR4 detect ?
- Detects LPS in bacteria
Where is TLR4 expressed ?
-Expressed in macrophages and dendritic cells (where the signal transduction process stimulates their maturation)
What happens when TLR4 detects LPS?
- Bacterium binding to the receptor stimulates a
signal transduction pathway - activates transcription of genes encoding for pro-
inflammatory cytokines
(e.g. TNF)
What does TLR7 detect ?
- detects single-stranded RNA (ssRNA) from viruses.
What happens when TLR7 detects ssRNA ?
- signal to activate signalling transduction inside the cell
•This leads to the production of IFNα and
IFNβ
•IFNα and IFNβ have anti-viral properties
What are the 3 key outcomes of the interferon (IFN-α, IFN-β) response during a viral infection?
- Inducing resistance to viral replication in all cells.
- Increasing expression of ligands for receptors on natural killer (NK) cells.
- Activating NK cells to kill virus-infected cells.
What are the functions of natural killer cells ?
• Activated by cytokines IFNαand IFNβ(Interferon)
• Kill cells infected by viruses (and some cancer cells)
• Can contain viral infections whilst adaptive/specific response kicks in
• NK cells can produce IFNγ (immunostimulatory,
immunomodulatory and effects on viral replication)
• Deficiency -> persistent viral infections and increased risk of herpes (rare)
How are NK cells activated and how do they affect cells ?
- IFN binds to IFN receptors expressed by NK cells, activating them
- NK cells proliferate and differentiate in effector NK cells
- Effector NK cells kill virus-infected cells by inducing apoptosis
What are antibodies ?
- Antibodies are the secreted form of the BCR
- The BCR and the antibodies are more generally known as immunoglobulins (Ig)
•
Structure of antibody ?
• Y-like shape
• Basic 4-polypetide chain structure
• 2 identical heavy chains & 2 identical light chains, held together by covalent and non-covalent bonds
• Each chain has a variable (V) region and constant (C)
regions
• Antigen-binding sites (variable region) consist of VH and VL and are part of the Fab (Fragment Antigen Binding)
• One Ig can bind 2 antigens
• CH regions interact with effector cells and complement and are part of the Fc region
what is the variable region of an antibody?
- specific to each antibody
what is the Fab region ?
- antigen binding
- top part of antibody
- made up of VH and VL
what is the Fc region ?
- constant region of heavy chains CH
- bottom half (only heavy chains)
- activates complement
How do the hypervariable regions in the VH and VL contribute to antigen binding in an antibody?
- 3 in VH and 3 in VL
- so 6 hypervariable loops when paired together forming a hypervariable surface
- this surface creates the antigen binding site
What are Complementarity-Determining Regions (CDRs) and how do they contribute to antibody-antigen interactions?
- CDR’s are the hypervariable regions in the VH and VL
- difference in CDRs between antibodies create the specificity and diversity of the antigen-binding sites.
- both the heavy and light chains contribute to the formation of the antibody’s antigen-binding site, enabling specific antibody-antigen interaction
what are the anti-bacterial specific functions of antibodies ?
- protect against extracellular bacteria through
- neutralisation
- opsonisation
- complement activation
How do antibodies protect against viruses?
- Neutralization: Antibodies bind to free viruses, preventing them from entering cells and spreading.
- e.g.= Influenza virus binds on cell surfaces through a protein called hemagglutinin.
- Neutralising antibodies coat the virus, inhibit its attachment and prevent
infection
Opsonization: increasing its recognition and phagocytosis - Complement Activation: leading to the lysis of enveloped viruses
What are the key functions of antibodies in the immune response?
- Neutralization (direct response to antigens)= Bacteria, Virus, Allergens
- Activation of complement (when antibody dependent)
- Opsonisation
- Activation of effector cells = Cells with Fc receptors
(NK cells, macrophages, neutrophils etc.)
Antibody –All functions
what are the 5 classes of antibodies ?
- IgG
- IgD
- IgA have 3CH domains,
- while IgM and IgE have 4CH
function of IgM ?
- First antibody to be produced
- Give the primary response
- Defense of tissues and prevention of septicemia (blood infection)
function of IgG ?
- Give the **secondary response **(more specific and stronger)
- Defense of tissues and prevention of septicaemia
function of IgA ?
- Prevents septicaemia
- Protects surfaces of the mucosal epithelium
- Present in maternal milk to give protection to infants
function of IgE ?
* Defense against parasite infections
* Important in allergies
function of monoclonal antibodies ?
- Immunosuppressive
- To prevent transplantation rejection
- To treat autoimmune disease
- To reduce immune response
- Produced in mice
