CMB1003/L22 Humoral Specific Immunity I Flashcards
Give another name for antibodies.
Immunoglobulins
Describe the basic structure of antibodies. (3)
2 identical heavy chains
2 identical light chains
Joined by non-covalent interactions and disulphide bridges
How are antibodies first expressed?
As membrane-bound B cell receptors in developing B cells
What terminals are the variable and constant regions of antibodies?
Variable - N-terminal
Constant - C-terminal
Where does cleavage occur in an antibody?
Hinge region
What does the Fab contain?
Fragment Antigen Binding
Contains antigen-binding region
What does the Fc contain?
Fragment crystalizable
Interacts with Fc receptors on cells with C1q
What are the main functions of antibodies? (2)
Bind specifically to epitopes of the pathogen/antigen that elicit immune response
Recruit cells and molecules to destroy the pathogen/antigen
Describe the binding of antibodies.
Fab region binds to epitopes of pathogen
Describe the possible conformations of epitopes. (2)
Linear
Conformational components of Ag.
Give 5 functions of an antibody.
Neutralise
Agglutinate
Opsonize
Activate complement
Improve phagocytosis
Antibody-dependent cellular cytotoxicity
Degranulation
What is the aim of neutralising antigens/toxins?
Prevent interaction with cell receptors
Prevent uptake of pathogen by target cells
What kind of cell neutralises toxins?
Macrophages
Why is agglutination useful? (2)
Impedes travel of pathogen
Alerts immune system more effectively
Describe how opsonization occurs.
Extracellular proteins binding to mark pathogen for destruction via phagocytosis
Describe direct opsonization.
Binding of antibody to constant region (Fc receptors) to phagocyte receptors
Describe indirect opsonization.
Increasing complement (C3b) deposition on pathogen and binding to complement receptors (CR1)
How does antibody binding activate the classical complement pathway?
Antigen-antibody complex binds C1qrs
Acts on C4 and C2 to generate C3 convertase
Describe ADCC (antibody dependent cellular cytotoxicity). (3)
Detection of antibodies by FcR on several cell types induces cell activation (degranulation)
Lyses target cells
Mainly NK cells
Descrive degranulation via Fc receptors (FcR). (2)
Degranulation of mast cells
Killing by NK cells and eosinophils (ADCC)
How are antibodies produced in the lab? (2)
Fuse an individual B cell with a B cell tumour line
Generate a hybridoma giving an unlimited supply of monoclonal antibody (mAb)
How can antibodies be used in the lab? (2)
Flow cytometry
Western blot
Immunofluorescence
How is a Western blot performed? (3)
SDS-PAGE
Transfer to nitrocellulose and overlay with antiserum
Detect bound antibody with enzyme-linked anti-IgG
What does flow cytometry achieve?
Identify cells based on panels of proteins they express
