2.4.9 B-cell immunity Flashcards
_____ is the important IL in the activation of B-cells (which now proliferate) and IL-____(2) play a role in differentiation of B-cells to plasma cells
IL4
-IL6, IL10
what are some major differences between resting B cell and plasma cell? (IgG, MHCII, Ig secretion)
Resting B:
- YES surface Ig
-YES surface MHCII
- NO high rate Ig secretion
Plasma cell
- NO surface Ig
-NO surface MHCII
- YES high rate Ig secretion
Naive T-cell recognizes _____ antigen and searches for specific antigen presented by ______ before it can start proliferating.
Naive B-cell recognizes _____ antigen and searches for specific antigen presented by ______ before it can start proliferating.
- Processed antigen, dendritic cell (hematopoietic origin)
- naive part of antigen, FDC (not hematopoietic origin)
does FDC process antigen?
NO
_____ covers virus particles due to complement activation, CR1 on FDC can now bind the virus and retain it at the cells surface.
C3b
C3b can be cleaved by ____ into ____ which can then bind to CR2 on FDC
Factor 1 cleavage
C3d
In the lymph node, the B-cell and TfH CD4+ T-cell will interact. Where can they go?
- medullar cords and B-cells differentiate into plasma cells
- back to primary follicle where the B-cells actively divide to form a germinal center
_______ in the __ region of the antibody molecule happens in the germinal center and results in Antibodies with high affinity
somatic hypermutation
V region
B-cells with high affinity ________
B-cells with low affinity __________
- can interact with antigen on FDC and T-helper at the same time, then differentiate into plasma cells
- die by apoptosis
Apoptotic cells engulfed by macrophages in the Germinal center are called _____
tingible body macrophages
explain the difference of B-cells that mature under the influence of IL10 Tfh cells vs IL4 Tfh Cells
- IL10 secreting Tfh
causes b-cell to differentiate into plasma cells that make antibodies
-IL4 secreting Tfh
causes B-cells to differentiate into memory B-cells which prevents future infections
what must the antigen be like for there to be T-independent response?
antigen consists of repetitive epitopes (lipopolysaccharides, capsular polysaccharides)
Is there usually class switching in T-independent response?
NO, mainly only IgM associated with B1 cells
why do T-independent responses only have IgM ?
class-switching requires T-cell help
the majority of antigens we encounter are _______, which results in _____ involving _____ cells
T-dependent antigens
class switching
B2 cells
In T-dependent responses what effect can these different cytokines have?
1. IL4
2. TGF-Beta
- induces IgE production
- class switching to IgA
IgM usually exists as a ______ and is found in the _______ defending against ______
- pentamer
- blood
- bloodborne pathogens
what are the polymeric antibodies that have J chains?
IgA and IgM
_____ is the major antibody class in blood and is the only class to cross the placenta
IgG
what are the 2 different IgG subclasses we need to know?
IgG1 - proteins - induce IgG1 response
IgG2 - polysaccharides - induce IgG2 response
what is the half life of IgG?
1 month
_______ responds to protein antigens while ______ responds to carbohydrate antigens
IgG1
IgG2
what happens in an in utero infection?
fetus can make IgM and IgG
there is a ______ receptor on the endothelial cell that binds to IgG that can then bring it to the extracellular space
FcRn
what is the IgD function?
there is none we know of
what is the IgE funtion?
associated with allergic reactions and important in parasitic infections
IgE can attach to ________ and also activate ______
-mast cells/basophils
-eosinophils
IgE helps _____ bind to parasite with _____ which then kills the parasite
eosinophils, Fc sigma RI
_____ is the major antibody class in external secretions. it also protects mucosal surfaces
IgA
IgA produced by plasma cells are a ______
dimer with J chain
IgA in blood are a ______
monomer without J chain
there is a ________ expressed on epithelial cells for IgA to be released out
Ig / J chain receptor
what happens in peoples bodies who cant make IgA?
many more IgMs because that is the other Ig that has J chain
The secretory component (SC) plays a large role in _____
active transport of IgA out
what Ig is found in saliva? in gingival exudate?
-S-IgA
-IgG
what is the ratio of IgA to IgG in saliva?
19:1
do patients with periodontitis have more IgG or IgA?
IgG
_______ can degrade S-IgA1 and make it non-functional
IgA protease
(oral pathogens can produce this)
which Igs can do these:
1. Neutralization
2. Opsonization
3. Sensitization for killing by NK
4. Sensitization of mast cells
5. activate complement system
- G, A
- G
- G
- E
- M,G
________ clump bacteria and enhance their removal (usually IgM)
agglutinins
______ enhance phagocytosis ; antibody coated microbes attach to Fc receptor on phagocytic cells (IgG most often)
opsonins
what else can be involved in opsonization? (its part of complement activation)
C3b
what two things can both be activated and result in an enhanced ability to do phagocytosis?
Fc receptor and C3b receptor
________ antibodies are Abs that neutralize viruses or bacterial toxins (IgG or IgA)
neutralizing antibodies
what are 2 examples of actions of neutralizing antibodies?
- antibody protects cell by blocking binding of a toxin
- antibody blocks binding to virus receptor and an block fusion event
_____ cause disruption of cell membrane and can activate complement system (IgG and IgM)
Lysins
______ antibodies prevent attachment of microbes to cells or hard surfaces (ex: S-IgA prevents bacteria from adhering to teeth)
Anti-adherance antibodies
______ plays a role in bringing IgG across the placenta and from blood –> tissue
FCRN
what is antibody dependent cell toxicity? (ADCC)
- antibody binds antigens
- Fc receptors on NK cells recognize bound antibody
- cross-linking of Fc-gamma-R3 - NK kills the target cell
In ADCC what is the other name for Fc-gamma-R3
CD16
_______ is used as part of targeted therapy in treating patients with B-cell leukemias and lymphomas
anti-CD20
______ tightly adheres to IgE antibody. this receptor is expressed by mast cells, basophils, and activated eosinophils
Fc-epsilon-R1
does IgE in blood have a long or short half life?
SHORT
How do RBC facilitate removal of immune complexes from circulation?
- antigen/antibody complex forms & activates complement
- immune complex coated with C3b
- CR1 (Fc-gamma-R1) on RBC binds C3b tagged immune complex
- RBC goes to liver/spleen and organs strip immune complexes and ingest/destroy them
