Acquired Immmunity-antigen Receptors Flashcards
Characteristics of the acquired immune system
Specificity, memory, variable intensity
What elements of the immune system bind and recognize antigens
Antibodies
T cell receptors
MHC molecules
The part of the antigen with which the antibody interacts is the ___
Epitope
Why is the epitope the antigeni determinant
Determines which antibody will bind
What are antibodies
Large glycoproteins
What is the T cell receptor
Large glycoproteins
Unlike an antibody that interacts with the whole intact antige, what do T cell receptors interact with
Short segment of aa, the peptide epitope, derived from the intact antigen proteolysis
Can T cells interact with soluble peptide epitope directly?
No peptide must be held and presented by other glycoprotein molecules, MHC
What are MHC
Glycoprotein
Hold the peptide antigen enclosed within a groove
So what is recognized by a T cell receptors
MHC and peptide epitope
What forces do antigens renter act with antibodies, TCR, and MHC
Non covalent
H bond and electrostatic attraction and van deer waals
Dissociation constant
Strength or affinity of antigen interaction
Concentration allowing half the antibodies to be completed and half to remain in solution
The smaller the Kd the ___ the affinity
Higher
Rank affinity for antigens of antibodies, MHD and T cell
Antibodies greater than MHC greater than T cell
How many sites does IgM have to bind
10, it has five arms
How many sites does igG have to bind
2, it has 1 arm
Avidity
Strength of attachment
If blood is clotted and removed from he plasma, what is left
Serum
Antigen binding site of antibody
Regions that are highly variable in their aa content in different molecules
Heavy chains
Antibodies have relatively constant parts, hold different functional properties such as ability to activate complement
Describe the basic immunoglobulin
Two heavy chains and two light chains connected by inter chain disulphide bonds…within the chains, distinctive motifs are formed by intra chain disulphide bonds
Immunoglobulin. Superego need family
Many immunological molecules have similar domain structures
Different heavy chains give rise to different classes. What are they
IgA, IgD, igE, iGG, IgM
Formula of an immunoglobulin
Heavy2Light2
There are two alternative types of light chain. What are they
Kappa and lambda
Either have two kappa(more common) or two lambda
What are the five heavy chain types
Alpha, beta, delta, epsilon, gamma, and mu
The 2 will be identical
Each heavy chain and light chain have a stable segment and a zone that varies a lot . What are they called
C region-constant (effector function such as complement activation
V regions-variable (antigen binding site
How may hypervariable of complementarity-determining regions(CDR) are in each heavy and light chain
3
To form the full antibody molecule, the two heavy chains are linked together by what
Two interchain disulphide bonds
Each heavy chain is attached to a light chain by what
Interchain disulphide bond
All immunoglobulin domains contain two layers of B pleated sheet with 3 or 4 strange of anti parallel polypeptide chain
Ok
Immunoglobulin supergene family
MHC, T and adhesion molecules have similar domain structure
V underscore H
Variable region heavy
C underscore L
Constant region light chain
Hinge region
Middle of molecule allows freedom to the two arms bearing the antigen binding sites …flexible
Papain
Enzyme cleaves at the hinge region , breaking the two interchain disuphide bonds between the heavy chains in the process, to produce three fragments
When cleaved by papain, describe the 3 fragments
2 Identical and retain antigen binding ability
Called Fab fragments (fragment antigen binding)
45kDa each
1 is larger (55kda) and cant bind antigen but retains effector function
It is crystal likable and termed the Fc fragment (bc can bind Fc receptor )
Pepsin
Enzyme that leaves the heavy heavy disulphide bond in tact cuts into two fragments
Describe the two fragments from pepsin digestion of antibody
F(ab’)2- 2 Fab fragments linked with antigen binding site, but no effector function remaining
How do we achieve variation of effector region
H chain
5 subtypes but gamma is further gone intoy1-4 and alpha a1-2
IgG and igA subclasses
IgG1-4
IgA1-2
What is the most abundant immunoglobulin
IgG
IgG2
Capsulitis bacteria
IgG1-3
Activators of the classical complement pathway
How can we increase the binding of C1q to igG
Bind igG to antigen
What domain does C1q interact with
CH2
The igG has three constant domains on the heavy chain. What are these called
CH1-3
IgG is a monomer and has how many classes
4
Half life of igG
23 days
Proportion of IgG in circulation
50
IgA structural form
Monomer (circulating )
Diner (secretory)
IgA accessory chain
J chain polyimmunoglobulin receptor (secretory chain)
IgA subclasses
IgA1, igA2
IgA heavy chain
A
IgA number of domains in heavy chain
3
IgA half life
6 days
IgA proportion in circulation
50
IgM structure
Pentamer
IgM accessory chain
J chain
IgM heavy chain
Mu
IgM number of domains in heavy chain
4
Half life igM
5 days
IgM proportion found in circulation
80%
IgD structure
Monomer
IgD heavy chain
Delta
IgD number of domains in heavy chain
3
IgD half life
3 days
IgD proportion in circulation
75%
IgE structure
Monomer
IgE heavy chain
Epsilon
IgE number of domains in heavy chain
4
IgE half life
2.5 days
IgE proportion found in circulation
5o
IgG adult serum concentration
6-12 g/l
IgA adult serum concentration
1-4g/l
IgM adult serum concentration
.5-2 g/l
IgD adult serum concentration
.04 g/l
IgE adult serum concentration
.003 g/l
Rank IgG based on proportion
IgG1 more than igG2 more than IgG3 more than IgG4