antibodies Flashcards
where do the immune system cells start
in the bone marrow
where do different immune cells go
to diff parts of body
the immune system is made up of what
a bunch of cells
immune memory comes from which cells
slow response cells
what is innate immunity
rapid response
what is adaptive immunity
slow response
name some innate immunity cells
macrophages
dendritic cell
mast cell
natural killer cell
complement protein
granulocytes:
- neutrophil
- eosinophil
- basophil
name some adaptive immnity cells
B cell - antibodies
T cell:
- CD4+ T cell
- CD8+ T cell
what cells are a mixture of adaptive and innate immunity
natural killer T cell
T cell
All cells of the immune system share what
share a common progenitor– the hematopoietic stem cell
Multipotent
(Multipotent cells become a certain group of cells , such as only becomes immune cells )
Rounds of differentiation and specialisation to cells produce
the vast array of ”white blood cells” that make up our immune system
The Lymphoid Lineage all start life where
doing what
in the bone marrow
receiving signals from stromal cells
such as T cells, B cells, and NK cells
where are T cells mature
Mature in the Thymus
Regulatory and Cytotoxic
where are B cells mature and what do they produce
Mature in the Bone Marrow
Produce antibodies
where are NK cells mature
Mature in the Bone Marrow, but also secondary lymphoid tissues
Cytotoxic
what is B cell development dependent on
on the transcription factor Pax5
In Pax5-/- mice, these progenitor B-cells can be transformed into T-cells and myeloid cells, suggesting that Pax5 is important for commitment to the B-cell development pathway.
what does The development of the B-cell, and thus the B-cell receptor, involve
a complex series of gene recombination to produce the vast array of antibodies we need
B cells make antibodies
Pax5 make b cells
how long roughly do antibodies take to develop
days to weeks
what is the instructive theory of antibody development
Linus Pauling -1940
The antigen acts as a template that directs the folding of the unfolded antibody chain
Thus, a specific amino acid chain has the propensity to form a variety of antibodies, depending on the antigen present at the time
what is the selective theory of antibody development
Macfarlane Burnet, Niels Jerne, David Talmage, and Joshua Lederberg – 1950s
The binding site of the antibody is already pre-determined before antigen is even encountered
The presence of antigen only affects how much of that specific antibody you get
name the 2 theorys of antibody development
instructive theory
selective theory
explain what the instructive theory would suggest
would suggest that if the antibody protein was unfolded and then refolded without antigen present it would lose its affinity.
7M Guanidine Hydrochloride an antibody against DNP-BSA was denatured
- DNP-BSA – highly immunogenic and useful for making antibodies to study
No affinity for DNP-BSA
7M Guanidine Hydrochloride is removed and the antibody re-folds
Addition of DNP-BSA shows the antibody continues to have affinity
Thus, the instructive theory was incorrect, and the binding of antigen is dependent on the amino acid sequence
explain the selective theory of antibody development
Each antibody producing cell makes a single kind of antibody, and this commitment is determined before antigen is even present
Each cell has a distinctive base sequence in its DNA that determines the amino acid sequence
As the cell matures, each antibody producing cell makes a small amount of cell surface-bound antibody. The cell is then killed if it binds to a molecule during foetal development – therefore preventing B-cells that act against self
Later, the mature cell is activated and begins to undergo clonal expansion when exposed to antigen
Heterogeneous cell population = heterogeneous antibodies
These clones then persist long after the disappearance of the antigen
name the different classes of antibody
IgA
IgD
IgE
IgG
IgM
describe the properties of IgA
found in mucous, saliva, tears, and breast milk, and gut.
protects against pathogens
describe the properties of IgD
part of B cell receptor
activates basophils and mast cells
alos are important for certain granulocytes to release those granules
describe the properties of IgE
protects against parasitic worms
responsible for allergic reactions
describe the properties of IgG
secreted by plasma cells in blood
able to cross the placenta to the foetus
describe the properties of IgM
Antibodies start life as igm
may be attached to the surface of a B cell or secreted into the blood
responsible for early signs of immunity
know the polypeptide structure
see image notes for help
its a Polypeptide as antibodies are proteins
in antibody structure what does Fab stand for
Antigen binding Fragment
its the top part of the structure
in antibody structure what does Fc stand for
Crystallisable region fragment
its the bottom part of the structure
describe the IgG antibody structure
Made up of 2 polypeptide chains:
- Light Chain
- Heavy Chain
- H2L2
Held together by disulphide bridge
Both chains consist of a variable region and a constant region:
- Variable = is between 1 – 108 amino acids
- Constant = 109 – C-terminus
VL and VH are very similar on what antibody
the same antibodies
what does the heavy chain consist of
consists of 3 equal thirds
CH1, CH2, and CH3 are very similar to each other
CL is very similar to what other domains
3 CH domains
The intrachain disulphide bond is located where on antibodies - homologous domains
in the same place on every domain of both the H and L chains
explain antibody immunoglobulin folding
Broad sheets of anti-parallel β-sheets
- Hydrophobic side chains are tightly packed between the sheets and held together with disulphide bridges
explain the constant and variable domains after antibodies immunoglobulin folding
Constant domains
- 3 β-sheets in one strand and 4 on the other
Variable domains
- 2 additional β-sheets
3 loops that compose the part of the antigen binding site, and are highly variable
what does translocation of gene mean
part of gene cut off and moved somewhere else
explain what 1965 – William Dryer and Claude Bennett
predicted about antibody diversity
Multiple Variable genes
1 Constant gene
These genes are separated, and one V becomes joined to the C during differentiation and maturation of the B-cell
explain what 1985 – Susuma Tonegawa confirmed about antibody diversity
Confirmed that V and C genes are far apart in the embryonic DNA and closely associated in B-cells
Immunoglobulin genes are translocated during the differentiation of B-cells
what is The number of different kinds of antibodies that can be made by an animal
give ex
in the millions
ex: Mouse
Several hundred genes for variable regions
~300 for the light chain
~300 for the heavy chain
That leads to 9x104 different specificities
there is a large discrepancy between the germline variation and adult variation, so there must be what generated
an ternate source generated during the lifetimes of an animal and the differentiation of its lymphocytes
explain V(D)J Recombination
The V gene does not encode for the entire polypeptide chain.
- Stops at amino acid 95
- 13 residues too short, as amino acid chain is 108 amino acids long
Light Chain:
The stretch of DNA that encodes for this region is found nearer the Constant region
An array of 4 J regions:
- J = Joining as it joins the V and C regions
- Encode part of CDR3
1 of the several hundred V genes can become spliced to one of the 4 J genes
- Further diversity added as this splicing can occur in different joining frames
Heavy Chain:
The heavy chain has an additional region – the D region
- D = Diversity region
- 15 genes within this region
- A D gene will splice with a J gene, which will then become spliced with one of the V genes
The enzyme deoxyribonucleotidyl transferase, a special polymerase that does not use a template, inserts extra nucleotides between the V and D regions
how many possible variations of antibody combinations are there when we look at the light and heavy chains
Light Chain:
- ~250 V genes
- 4 J genes
- At least 3 possible joining frames
- 250 x 4 x 3 = 3000 possible variable combinations
Heavy Chain:
- ~250 V genes
- 5 J genes
- 15 D genes
- At least 3 possible joining frames
- 250 x 5 x 15 x 3 = 56,250 possible variable combinations
3000 x 56,250 = 1.7x108 possible variations of antibody combinations
explain Class Switch Recombination
B-cells begin life producing only IgM
- Class Switching recombination is needed to produce the other types of antibody
The constant regions of the heavy chains vary
Different classes of heavy chains depending on the antibody type:
- G – γ
- M - µ
- A – α
- D - δ
Somatic Hypermutation results in mutations being introduced into what region
into the V region of the heavy chain and light chain, altering the affinity of the immunoglobulin for its antigen
in Class Switch Recombination, the initial heavy‐chain C regions are replaced by what
another isotype, modifying the effector activity of the immunoglobulin but not its specificity.
somatic hypermutation and class switch recombination occur where as what
occur in secondary lymphoid tissues as part of the Germinal Centre reaction
Requires other cell types:
- CD4+ T-cells
- Dendritic Cells
- Produces long lived plasma cells that produce antibodies with a high affinity for the target antigen
in the The Germinal Centre reaction what makes the dark zone darker
more cells that it has
what happens to many B cells from the The Germinal Centre reaction
they dont grow or change but just exist
what cells produce the high affintity antibodies
Long lived plasma cells
name some practical uses of antibodies
Staining:
- Microscopy
- Flow Cytometry
- Western Blotting
Antigen Capture:
- ELISA – measures how
much of a protein you have in a sample
Drugs:
- Highly specific to the target, so reduced off-target effects
- ex Chemotherapy
