Week 17: (A) Immunoglobulins Flashcards
What are the 2 main components of adaptive immunity?
cellular immunity and antibodies
How do antibodies (immunoglobulins) work?
recognise antigens
What is an antigen?
any substance that elects an immune response
What is the portion that an antibody can recognise?
epitope/ antigenic determinant
How many macromolecules make up a micro-organism?
many
How many antigenic points are there on each macromolecules of a microorganism?
many different antigenic sites on each macromolecule
Where are immunoglobulins present?
plasma, tissues, secretions, lymphatic system
What are immunoglobulins the products of?
humoral immune system (a part of the adaptive immune system)
What are immunoglobulins secreted by?
activated B cells= plasma cells
What are the 5 classes of immunoglobulins?
IgG IgM IgA IgD IgE
What are the 2 functions that all immunoglobulin classes provide?
recognition
effector (get rid of foreign material recognised)
What is the N terminal of the light and heavy chains called?
variable region
What is the C terminal of the light and heat chains?
constant region
What holds the heavy and light chains together?
disulphide bridges
What holds the heavy chains together?
interchain disulphide bridges
What was the enzyme papain used for?
found to cleave the upper and lower parts of the structure
What are the upper parts of an antibody called?
Fab = fragment antigen binding - response for binding antigen
What are the lower parts of the antibody called?
fragment crystallisable - responsible for effector function
Why is the hinge region called the hinge region?
it affords lot of flexibility within the molecule, Fab move distinctly from the Fc region
What are the 2 types of light chains?
lambda and kappa
In an individual antibody are both light chains the same type?
YES
What does the heavy chain determine?
the class of antibody
What do the antibody chains fold up to form?
globular domains
How many chains does the light chain fold up to form?
2 globular domains
How many domains does the heavy chain fold up to form?
4 or 5 globular domains
What is the structure/features of each domain?
2 beta sheets. linked by a disulphide bridge to form a beta barrel
What is the folded structure of an antibody known as?
immunoglobulin fold
What are the names of the heavy chain globular domains?
VH, CH1, CH2, CH3 (and CH4)
What are the names of the light chain globular domains?
VL, CL
What are the close pairing of domains?
VH+ VL
CH1+ CL
CH3 +CH3
Why do the CH2 domains not pair?
immunoglobulins are glycosylated
The region lying between the 2 CH2 domains in IgG, N-linked oligosaccharides (sugar moiety’s) lie of inner surface of domain and stabilise the pairing
Why are they n-linked oligosaccharides?
attached to the Asn residues in the sequence Asn-X-Ser/Thr where X is any amino acid except Pro
What is the N-linked consensus attachment sequence for an N-linked oligosaccharide in any protein?
Asn-X-Ser/Thr
What position is Asparagine on a IgG?
297 in the heavy chain, where n-linked oligosaccharides are attached.
What is the immunoglobulin fold?
aka immunoglobulin domains
2 layer sandwich of 2-7 antiparallel beta strand, layered into 2 beta sheets
