Lecture 9 - B cell response/antibodies Flashcards
Humoral immunity
antibody-mediated
why does the plasma cells have more space
needs for endoplasmic reticulum and antibody synthesis
If immature B cells do not find an antigen they
leave the bone marrow
if BCR binds to self-antigen they
are eliminated via apoptosis or undergo receptor editing
If a B cell is still reactive to self antigens following receptor editing they
undergo apoptosis
Central tolerance of B cells refers to
The double-positive system before leaving the bone marrow
Transitional B cells are
B cells that have exited the bone marrow into circulation
Peripheral tolerance of B cells refers to
Single positive system of B cells maturation in the spleen
Transitional B cells with no strong self reaction
mature
what is the final stage of B cell maturation
upregulation of surface IgD
summarize the stages of B cell development
1 - stem cell in bone marrow
2 - pre B cell in lymphoid organs
3 - immature B cell obtain membrane IgM and IgD
4 - mature B cell in secondary organs obtain antigen
5 - plasma cells secrete immunoglobulins
T/F: other species have peyer’s patches but they are not the primary organ like in pigs
True
Fc receptors bind to
the B cell membrane
complement receptors do what
regulate
cytokine receptors do what
co-stimulate and regulate
BCRs consist of
immunoglobin domains
what domain of the BCR is the antigen-binding site
light chains
what are the signal transduction components of BCR
CD79 alpha and beta
how are BCRs and TCRs similar
antigen-specific
respond to epitomes presented in the linear form
How are BCRs different from TCRs
recognize free-floating native (3D) antigen, giving them more binding variety
Summarize activation of helper T cells via B cells
1 - antigen binds to BCR and is ingested
2 - antigen is bound to MHC II
3 - MHC II is presented on the membrane to TCRs
where are antigens presented to B cells
lymph nodes
How are B cells activated
dendritic cells present linear antigens or unprocessed native (3D) bind
summarize T cell-independent B cell activation
1 -polyvalent antigen binds to multiple BCR
2 - production of IgM (low affinity)
Summarize cross-links
1 - native antigen endocytosed
2 - expressed by B cell MHC II (exposure tp PAMPs and complements upregulate stimulatory molecules)
3 - processed epitopes to CD4+ T cells
4 - TCR binding induces CD154 expression
5a - CD154 binds to CD40 on B cell promoting immunoglobulin synthesis and proliferation
5b - CD40 promotes CD86 expression on B cells
6 - CD86 binds CD28 on T cell
7 - IL4 cytokine production
what does IL4 cytokine production give as an effect of cross-links
B cells differentiate
what mediates class switching of IgM to another immunoglobin
cytokines
T/F: B cell immunoglobins are controlled by T cells
True
what determines an immunoglobins isotype
1/5 heavy chains
Immunoglobin structure
2 heavy and 2 light chains
What immunoglobins lack a hinge region? what do they have instead?
IgM and IgE; extra heavy chain
IgM
immature b cells and antigen-specific BCR
primary immune response
can activate complement
IgG
B cells in secondary response
can activate complement
IgA
mucosal surfaces, secreted by MALT
secretory component
CANNOT activate complement
IgD
immature B cells; function unclear
IgE
immunity to parasitic worms and allergies
forms cross-links
CANNOT activate complement
Fc fragments mediate what functions
- complement activation
- opsonization
- cellular activation
What are the 5 biological functions of antibodies
- neutralization of microbial actions/toxins
- opsonization
- NK kills antibody-bound cells
- lysis of abnormal cells
- IgE activation of mast/eosinophils
what part of the antibody is variable
antigen-binding site
VDJ
heavy chain
VJ
light chain
What recombination occurs in terminal differentiation
light chain rearrangement
Summarize affinity maturation
- B cells activate
- mutation initiated by AID, turning cytidine to uridine
- error-prone DNA polymerase fixes uridine presence introducing further mutations
- changes arise in variable regions
- B cell with highest affinity to antigen differentiates to plasma cell
What does affinity maturation contribute to
improved antigen binding abilities of antibodies
What is isotype switching
activated B cells switch from producing IgM/IgD to IgG/IgA/IgE
Thelper 1 cell induce what isotype
IgG
Thelper 2 cell induce what isotype
IgE
Treg cells induce what isotype
IgG
what does isotype switching improve
antibody function in the Fc region
B1 cell characteristics
less common
spontaneously produce IgM/”natural antibodies”
target lipids/carbohydrates
The binding of Fc antibody portions to their receptors can trigger what sorts of actions
- phagocytosis/killing
- degranulation
- downregulate inflammation
T/F: antibodies are found bound to their Fc receptors
False
