2.7 Flashcards
what antibodies are in saliva
SIgA & IgG
what is the function of the antibodies in the oral cavity
limit bacteria adherence
what do B cells express
B cell receptors (BCR)
how are BCRs formed
by membrane-bound antibodies in association with invariant membrane proteins Ig alpha and Ig beta
how do BCRs recognize antigens
via membrane Ig
how do BCRs transmit signals
via Ig alpha and Ig beta
what is an isotype based on
the heavy chain
T cells and B cells recognize different forms and types of antigens and B cells may or may not need T cells to be activated. What is the specificity of B cells that develop in a T cell-dependent manner?
a - nucleic acid
b - lipid
c - protein
d - polysaccharide
e - hapten alone
c - protein
what Ig’s are monomeric with 2 binding sites
IgD, IgE, & IgG
what Ig is pentameric with 10 binding sites
IgM
what Ig is mainly dimers with 4 binding sites
IgA
what is the structure of immunoglobulin
y shape molecule formed by 2 heavy chains and 2 light chains
what are the two forms that immunoglobulin can exist in
membrane-bound or secreted
what do variable regions contain
antigen-binding sites
what does the constant region of Fc region mediate
effector function
what is the function of the constant region of the Fc region
- determine isotype
- bind complement
- bind Fc receptors
what is defined as the variable domains of light and heavy chains
binding site
an antibody binds a wide variety of antigens including what types
- proteins
- lipids
- polysaccharides
- nucleic acid
what is recognized by the antibody
the native not processed antigen
what is defined as the antigen part recognized by an antibody
epitope
how is the diversity of BCR generated?
recombination of Ig gene segments and junctional diversity
what does the heavy chain locus contain
V, D, J, & C genes
what does the light chain locus contain
V, J, & C genes
what does C gene organization lead to production of
IgM
what is the first C region cluster
Cµ
recombination of immunoglobulin genes involves
random selection of segments
what is the first antibody to be produced by the C gene
IgM
what is immunoglobulin gene recombination mediated by
recombinase (RAG) specific for VDJ
what does RAG deficiency lead to
SCID - bubble boy
the combinatorial diversity of Ig is ___
limited
the junctional diversity of Ig is ___
unlimited
what impacts junctional diversity
- exonucleases
- terminal deoxyribonucleotidyl transferase (TdT)
Ig has tremendous ____ but produces ____
- diversity
- nonfunctional genes
maturation of lymphocytes involve steps of ___ and ___
- proliferation
- receptor expression
immature cells that do not ___ functional receptors die by ____
- rearrange
- apoptosis
____ undergo negative or positive selection
mature cells
what is checkpoint 1 for B cell maturation
pre-BCR
what is checkpoint 2 for B cell maturation
IgM
selection of immature B cells occurs in the ___ in an antigen-independent manner
bone marrow
expression of ___ promote survival of B cells & proliferation and triggers recombination of the light chain locus & IgM expression
pre-BCR
signals from ___ promote survival of B cells
IgM
what does receptor editing involve
light chain recombination
what is the result of receptor editing
change of the Ig specificity
what is the advantage of receptor editing
B cells are not eliminated
____ eliminates immature B cells that can bind with high affinity ubiquitous self antigens
negative selection
____ results in clonal expansion and differentiation
antigen recognition
where do plasma cells producing high affinity Ig migrate to
bone marrow or mucosal tissues
how long do plasma cells producing high affinity Ig survive
years
_____ do not secrete Ig
memory B cells
what lasts a lifetime in mucosal tissues and blood with no restimulation
memory B cells
what distinguish B cells from T cells?
a - BCR diversity is not achieved by random rearrangement
b - selection of B cells depends on antigen recognition
c - expression of pre-BCR in contrast to pre-TCR induces cell survival
d - receptor editing only occurs for B cells
e - T cells recognize native proteins
e - T cells recognize native proteins
what antibody response is quicker, larger, has higher affinity, and more abundant IgG
secondary
what provides signal 2
innate immune signals
what does signal 1 involve
engagement of antigen receptor
what does signal 2 involve
engagement of CR2 or TLR enhancing B cell activation
what delivers the CR2 activating signal
CD19 & CD81
what type of antibody response is to protein antigens
T dependent
what type of antibody response is to nonprotein antigens
T independent
what type of antibody response involves isotype switching
T dependent
what type of antibody response involves IgM
T independent
what type of antibody response involves high affinity Ig
T dependent
what type of antibody response involves low affinity Ig
T independent
what are small molecules that cannot elicit an immune response by themselves but do so after binding to larger proteins or cells
haptens
___ process antigens
B cells
T/F B cells and T cells recognize different epitopes of the same protein
true
native conformational epitopes are recognized by ___
B cells
peptide fragments are recognized by ___
T cells
what does recognition of peptides presented by B cells induce
CD40L upregulation in T cells & production of cytokines
engagement of CD40 and cytokine receptors on B cells lead to their ____ and ___ in plasma cells
- proliferation
- differentiation
what occurs in the germinal center?
- isotype switching
- affinity maturation
- selection of high-affinity B cells
what induces isotype switching
change in the constant region of the heavy chain with no change in specificity
what does isotype switching require from Tfh cells
CD40L
how is the type of heavy chain isotype determined
by the cytokines produced by Tfh cells (IgG & IgE) or tissues (IgA)
T/F in switch recombination the specificity of the Ig changes
false - does NOT change (same V region)
in switch recombination what is different and what does it reflect
- C region
- function of the Ig
what results in the deletion of Cµ gnee
activation-induced cytidine deaminase (AID)
activation-induced cytidine deaminase results in recombination bringing ___ next to a different ___
- VDJ exon
- C gene
how are FDC different from classical dendritic cells
- different progenitor
- no processing of antigen
- no binding of antigen to MHC molecules
what do high-affinity B cells interact with
- follicular DC that display antigens
- Tfh that promote survival via CD40-CD40L
