13 - B Cells And Antibodies Flashcards
B cell info at start here…
…
Antibody basic structure
- tetrameric
- four polypeptide chains - 2 identical heavy chains and two identical light chains
- chains held together by covalent disulphide bonds at hing and between heavy and light chains
Advantage of antibody structure
Allows multiple antibody/antigen interactions
- as one antibody tetramer can bind two identical antigens
- hinge region - can cross-link antigens
Binding of antibodies with two identical antigenic determinants
Antibodies can cross-link the antigens
- make small cyclic complexes or linear complexes
Different antibody/antigen interactions
- one antigenic determinant
- two identical antigenic determinants
- three or more identical antigenic determinants
- three or more different antigenic determinants
3 or more identical antigenic determinants
3 or more different antigenic determinants binding with antibody active sites
Different classes of antibodies/immunoglobulins
- collective name for antibodies is immunoglobulin
- mammals usually make 5 classes of Ig(immunoglobulins)
Different classes: - IgM -
- IgD -
- IgG -
- IgA -
- IgD -
Why IgM is considered an opsonin
- how does IgM work
- IgM is very efficient at activating complement
- can direct complement for direct killing of pathogens
- can mark antigens with complement for phagocytosis
What is an opsonin
Any molecule that targets antigens for phagocytosis
- complement is also an opsonin
- coating of a target with IgM (or other antibodies) or complement is called opsonisation
IgG structure
IgG functions
Which immunoglobulins can pass through the placenta, into foetal blood
Some IgG subclasses
Passive immunity from IgG in foetal blood
What can IgG also be
Opsonin
- bind and coats pathogens
- phagocyte receptors recognise and bind the tail region (Fc) of bound IgG antibodies
- results in phagocytosis stimulation
