B cells and Antibodies Flashcards
definition of antibodies (imunoglobulins)
proteins made and secreted to bind with antigens. Once bound, helps inactivate/clear out microbial (or non-microbial) agent
Ig structure
2 identical heavy chains and 2 identical light chains
light chains isotypes and their frequnecy
kappa (60%), lambda (40%)
heavy chain isotypes
α - IgA 1, 2 δ - IgD γ - IgG 1, 2, 3, 4 ε - IgE μ - IgM
FAB
fragment antigen binding: portion of antibody that binds antigen
FAB is produced by digestion of Ig with what enzyme?
Papain
Fc
Fragment crystallizable: effector function of Ig, binds with other things that have an Fc receptor
Fc contains which portion of the antibody molecule?
C-terminal portion
F(ab’2) and produced by which enzyme
Bivalent FAB fragment, produced by pepsin
Ig molecule consists of how many FAB and Fc fragments?
2 FAB and 1 Fc fragment
how many hypervariable regions (CDRs) are on each light and heavy chain? How many in total on an Ig?
3 on light chain, 3 on heavy chain, a total of six
Basis of specificity for antigen
HV regions = CDRs (complementarity determining regions)
What makes up one FAB region?
VL, VH
CL1 CH1
How many variable (heavy and light) domains are on an Ig?
On variable heavy, one variable light on each half of Ig, so in total, 2 VH and 2 VL
How many Constant light domains are on each Ig?
One CL on each side of Ig, so a total of 2 CL domains
How many constant heavy domains are there on each Ig? Which two Igs are an exception
3 constant heavy domains on each side, so 6 in total. IgM and IgE can have a fourth constant heavy domain
less variable regions aligning hypervariable regions that provide structural integrity to variable domains
framework residues
Isotype
constant regions of heavy/light chains
idiotype
antibodies with different variable domains
Igs that are complement activators
IgG and IgM
B-cell membrane receptors (mature cell)
IgM and IgD
First antibody during immune response
IgM
The only antibody produced by immature B-cell
IgM
2 fates of IgM and structural form for both
- plasma membrane bound, serves as B cell receptor for antigen or B cell activator (monomer)
- secreted from plasma, potent activator of compliment classical pathway (pentamer)
Second isotype of Ig produced
IgD
very similar to IgM but contains different Fc portion
IgD
the “glue” that hold a pentamer Ig together
J-chain
Ig with highest serum concentration
IgG