Humoral immunity(Generation of antibody diversity) Flashcards
What are antibodies?
• Y shaped molecules expressed by immune cells to target pathogens
How do antibodies work?
• Antibodies work by preventing bacteria entering by binding to the bacteria docking site or neutralizing them
Antibody structure?
2 heavy, 2 light chains
How many classes does the heavy chain have and what are they divided into?
○ Heavy chain has 5 classes: μ,δ,γ,α or ε chain
§ Divided into subclasses: γ1, γ2, γ3, γ4
§ Divided into subclasses: α1, α2
How many domains, constant and variable regions does the heavy chain have?
§ Heavy chains have 4 domains: 3 constant and 1 variable region
How many classes does the light chain have?
Variable region is very specific – binds to specific epitopes of specific antigens
How many variable and constant regions does the light chain have?
§ 1 variable region and 1 constant region
What is the variable region and what does it bind to?
Variable region is very specific – binds to specific epitopes of specific antigens
What is constant region very responsible for?
• Constant region is very responsible for biological activities
How many forms do antibodies have and what are they?
○ B cell receptor and secreted form
What is the final form and whats it used for?
The final form is the secreted form – used to fight off pathogens
What is the final form of antibody anchored to
It is anchored to plasma membrane of B cells
What forms can the antibody be when secreted?
§ When antibody is secreted it can be monomeric forms or pentameric forms
What is antibody initially secreted as?
§ Initially secreted as a monomer and then combined to produce a multimeric form
Where do B cells spend its life?
• B Cell spends its life in bone marrow, blood, spleen and secondary lymphoid organs
What can the life cycle of B cells be divided into?
• Life cycle can be divided into antigen dependent and independent stage
Steps involved in the lifecycle of B cells
- Start with stem cell which differentiates into pro B cell
- Pro B cell undergoes VDJ recombination which codes in the heavy chain constant and variable region and becomes a pre-B cell
• Once it makes a functional heavy chain, it becomes a pre-B cell - Then it undergoes another VDJ recombination to code in the light variable and heavy chain regions
- B cell continues to mature until it expresses IgM and IgD
- Becomes a mature circulating B cell and then becomes activated once it encounters a pathogen
- B cell migrates into germinal centre (GC) and will undergo a special selection to hone its variable region to that particular pathogen
- Undergoes affinity maturation and class switching
- Differentiates into plasma cells which secretes antibodies and memory B cells
What are somatic recombinations and an example?
• Any changes at the DNA level are called somatic recombination e.g. VDJ recombination
What is differential splicing?
• Changes at the mRNA level are called differential splicing
What is each chain of the antibody made of?
• Each chain is made of one single polypeptide
What is the hinge region between in antibodies?
Hinge region is between CH1 and CH2
What makes the antibody flex and so what does this expose?
○ These are a stretch of polypeptides that make the antibody flex so that the active site can be exposed
What chain is the hinge region longer in?
○ Hinge region is longer in heavy chain
What are Fv regions?
○ Variable regions of light and heavy working together