Antibody structure and B cells Flashcards
What are antibodies (Ab)?
also known as immunoglobulins (Ig)
Ab are the targeted weapons of the adaptive immune system
clear extracellular pathogens and neutralise toxins
where are antibodies produced
by activated, effector B lymphocytes (plasma cells)
where do antibodies circulate/ found
circulate in plasma and lymph and are found at mucosal surfaces
are antibodies specific
yes they bind only to a single antigens (Ag)
how large is the antibody repertoire
very large – 109-1016 unique molecules
why do B cells have surface antibodies
how Plasma cells secrete antibodies
describe the structure of an antibody
constant regions (bottom half of top)
variable regions (top of top)
hinge region
two identical Ag-binding sites
bivalence (can bind two antigen molecules at the same time)
describe Antibody ‘dissection’
does The hinge region gives flexibility
true
describe Structure of human Ig classes
GAMED
what are antibodies made of
compact protein complexes made up of immunoglobulin (Ig) domain
in 3D Ig domains in 3D – the light chain
antigen binding domain recognises a 3D shape not an aa sequence
explain how Antigen binding – hypervariable (HV) regions
complementarity-determining regions CDR
flanked by framework regions (yellow)
There are 3 HV regions in each V domain
Come together at the ‘tip’ of the Ig molecule
Since antibodies are bivalent and the antigen binding region is made of variable regions of heavy and light chains, there are 12 CDR per antibody
true or false antibodies bind to epitopes on a pathogen surface
true
Antigen binding - shapes
Epitopes can bind to different surfaces in the Ag binding site
- depends on complementary surfaces
Epitopes can be linear or conformational
how is antinodie diversity generated
Immunoglobulin genes are made up of gene segments
pick and mix
Each set of segments contains alternative versions
Gene segments must be rearranged to form a functional gene
This occurs during B cell development in the bone marrow
- All rearrangements are by chance
_ BEFORE antigen is seen
explain how and where random recombination could occur
does Functional sequences arise by rearranging gene segments
true
how it happens simply slide
describe how Immunoglobulins change AFTER antigen encounter
Antigen binding to the membrane-bound immunoglobulin triggers
proliferation, activation and differentiation
secretion of Ab
but only with T cell help
Ultimately, activated B cells become
plasma cells
memory B cells
As immune responses progress, both the antigen binding and effector functions of the antibody will change
what do B cells do once they leave the bone marrow when mature…
and circulate through the lymphatic system, looking for Ag and T cell help
explain the Stages of B cell activation and maturation (simple)
TF control b cell stage activation that can go on to become a memory cell or plasma cells
