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73 Cards in this Set

  • Front
  • Back
Types of antigen displayed on CLass II MHC:
Type of cell that responds to Class II MHC / Ag:
Thelper CD4+
Thelper becomes:
either Th1 (IL12) or Th2 (IL4)
Thelper 1 secretes:
Cells stimulated by Th1 cytokines:
Th1 does what to macrophages:
Activates them to increase their ability to phagocytose and kill
Th1 does what to Bcells:
Stimulates isotype switching to IgG1 and IgG3
Th2 cells secrete:
IL4, 5, and 10
Th2 cytokines stimulate what cells?
B cells
What does Th2 stimulation of Bcells do?
Stimulates isotype switching to IgG2, 4, and IgA and IgE
Viruses are presented by what MHC
what cells respond to viral antigens on MHC I?
CD8+ Tc cells
What do CD8+ Tc cells do?
Kill the infected cells either independently or with Thelper help
When is CD4+ Thelper help needed for CTL differentiation?
When the antigen presented on MHCI is in too low of concentration.
What are the functions of class switching to IgG1 and IgG3 stimulated by Th1 cells?
To function as opsonins and activate complement.
What marks a Bcell as mature?
The presence of both IgM and IgD
What are the 2 phases of antibody response?
When does a primary Ab response occur?
Upon initial infection
When does a secondary Ab response occur?
Upon repeat infection
Where do naive Bcells first see antigen in a first infection?
In lymph nodes, out near the cortex.
What happens to Bcells upon initial recognition of antigen?
They become activated if sufficient costimulatory molecule is expressed on the APC
What happens to activated Bcells?
They secrete antibody in peripheral lymphoid tissues.
How many days usually follow the initial infection before antibody secretion begins?
5-10 days
What is the prominent antibody that is secreted in a primary response?
IgM > IgG
What is the antibody affinity like in a primary response?
Lower than average, and more variable.
How many days usually follow a repeat infection before antibody secretion begins?
only 1-3 days
What is the peak response in a secondary response compared to primary?
Much greater
What is the predominant antibody made during a secondary response?
IgG, or IgA/IgE in certain situations.
What is the antibody affinity like in a 2ndary response?
Higher than average affinity.
Why is affinity higher in a secondary response?
Because of affinity maturation.
Are cell-surface associated immunoglobulins capable of signal transduction?
What molecules transduce the signal into Bcells?
Ig-alpha and Ig-beta
What happens when Ig-a and Ig-B transduce a signal into the Bcell?
Tyrosine phosphorylation cascades which cause enzyme upregulation and transcription factor stimulations.
What are the steps in Bcell activation?
1. C3d binds microbe
2. BCR (Ig) binds microbe
3. Bcell CR2 binds complement coating the microbe
What is the purpose of the complement protein C3d coating microbe and binding to the Bcell's CR2 receptor?
It serves as the 2nd signal for Bcell activation.
What are the main consequences of Bcell activation during a primary infection?
1. Clonal expansion
2. Increased expression of B7 and cytokine receptors
3. Migration out of lymphoid follicles to interact w/ Th
4. Secretion of low amts IgM
Why would you want activated Bcells to express more B7?
So they can stimulate Thelper cells more effectively - remember Bcells act as APCs too
What does T:B interaction during a primary infection consist of?
1. Activated Bcells migrate from follicle to paracortex
2. Present Ag to Thelper cells, along w/ B7 to CD28
What is the Thelper response to antigen presentation by Bcells?
Proliferation, differentiation, and depending on the cytokine environment C' activation/inflammation or IgE class switching.
What do activated Bcells do after interacting with Tcells near the paracortex?
They migrate back into the follicle.
How can Bcells act as APCs?
They swallow up the microbes that crosslink the surface Ig's by receptor mediated endocytosis.
What MHC do Bcells present antigen on?
What is needed for Bcells to properly activate Tcells?
1. Antigen presentation
2. B7 binding to CD28
Can B:T interaction occur during a primary antibody response?
No; there are not enough B clones proliferated yet to present sufficient amt of Ag to Tcells to activate them.
What do we call the space between a T and Bcell during interaction?
Immunological synapse
What is the key molecule that is expressed by activated Tcells in response to Bcell antigen presentation?
-cytokines secreted
What happens when the CD40L on Tcells engages with the CD40 on Bcells?
Cytokines from the Thelper cell cause Bcell proliferation and differentiation
What is the principal effector function of IgM?
Complement activation
What are the 3 functions of IgG1 and IgG3?
1. FcR-dependent phagocytosis
2. Complement activation
3. Neonatal immunity
What are the 2 principal functions of IgE?
1. Immunity against helminths
2. Mast cell degranulation
So the hypersensitivity that IgE is involved in is:
Immediate Hypersensitivity Type I
What is the principal effector function of IgA?
Mucosal immunity
What are the 3 changes that can occur to an antibody's structure during its lifetime?
1. Affinity maturation
2. Switching from membrane to secreted form
3. Isotype switching
Where does affinity maturation occur?
In Bcell germinal centers
What is the basis of affinity maturation?
In germinal centers, only the b-cells with high affinity for the Ig antigen survive
What cells present Ag to activated Bcell clones in germinal centers following an antigen stimulation?
Follicular dendritic cells
Toward the end of antibody production when lots of Ab-Ag complexes are around, how does the Ab reaction stop?
By binding of Ab-Ag complex Fc regions to FcR's on Bcells
Is T:B interaction required for antibody secretion?
How can Bcell production be stimulated in the absence of Tcells?
By Thymic-Independent antigens
What are the types of Thymus-Independent antigens?
TI-1: polyclonal activators of Bcells at high concentrations

TI-2: polysaccharide activators with repeating subunits (epitopes)
What do Polyclonal Bcell activators stimulate at LOW concentrations?
Specific antibody
What types of Bcells are stimulated by polyclonal activators?
Both immature and mature Bcells
What is the best example of a TI-1 polyclonal activator?
What type of antibody is secreted in response to a TI-1?
What type of activation results from polysaccharide epitopes?
What is the best example of a TI-2 epitope?
Baccterial capsular polysaccharide
What type of antibody is secreted in response to a TI-2 stimulation?
Does isotype switching of antibody occur in response to TI-1 antigens? TI-2?
TI-1: yes
TI-2: NO
Does affinity maturation occur for TI-1 antigens or TI-2?
TI-1 only
Is there a 2ndary response upon repeated exposure to TI-1 or TI-2 antigens?
TI1: yes
TI2: only with certain epitopes
Where are isotypic differences on antibodies found?
In the Fc regions of the heavy chain
Where are allotypic differences on an antibody found?
In the Fc region, but these are only single AA differences
Where are idiotypic differences found?
At the variable regions of both heavy and light chains.