Lecture 20-21: Immunoglobulin Flashcards
What are the two regions of an immunoglobulin
- variable region
- constant region
What functions does the variable region do?
- mediate antigen bonding
- differ between immunoglobulins
What functions does the constant region do?
- effector functions
- conserved between immunoglobulin of one isotype
What is the structure of immunoglobulins
- 4 polypeptide chains, 2 light and 2 heavy
- held together by disulphides linkages
What two things can digest immunoglobulins
- papain
- pepsin
What does papain do
- breaks it into three parts
- Fab which can bind the antigen
- Fc which is crystallized
- unable to precipitate antigen
What does pepsin do?
- F(ab’)2 binds and crosslinks antigen
- Fc fragment is not recovered
- able to precipitate antigen
What are complementarity determining regions
Regions that form loops and bind to the antigen
What are framework regions
Remaining variable domain regions
What do CL and CHL do?
- add flexibility to antigen binding
- stabilize H-L chain interactions
What is CH(2-4)?
-hydrophilic
What are idiotypes
Collections of antigenic determinants in the variable region
What is a idiotope
Each individual determinant is known as an idiotope
What are Ig alpha and Ig beta
Ig binds with them and it helps generate signals through immunoreceptor tyrosine-based activation motifs
What can an Ig bound to an Ag activate in a pathway?
Complement, must bind to two at the same time
How do antibodies neutralize
It coats a target in antibodies prevents them from adhering to cells
Explain Fc receptors
Ig bound to bacteria is able to cross link Fc receptors which generated a signal
What can binding of Fc receptors do
- phagocytosis (opsonization)
- Ab dependent cell mediated cytotoxicity
- granulocyte degranulation
What is Ab dependent cell mediated cytotoxicity
Binding of NK cell to Fc starts a release of cytotoxic stuff that kills a target
What is granulocyte degranulation
Cross linking of the Fc bound IgE by an antigen induces degranulation
What is the lifespan facts of a B cell
- continuously produced throughout life
- short half life’s of 3-4 days
- they must encounter an antigen to survive
Where are B cells produced and where do they hang out
Bone marrow and lymph node
What is hypermutation
Process by which B cells are mutated to bind with antigens
In germinal centres what are the two zones
The dark zone which is dividing centroblasts and light zone which is selection and maturation of centrifuged
What B cells are picked for survival
Centrocytes with high affinity receptors are selected for survival and will die unless they bind to antigens
