B-Cell Immunity Flashcards
What are the two types of responses to antigen when B cells are activated?
1-Thymus-dependent antigen (most common, response against a protein)
2-Thymus-independent antigen
What are the two types of Thymus-independent antigen?
1-TI-1 (multivalent, polymerized antigens recognized by PRR)
2-TI-2 (highly repetitive antigens bound by the complement C3d)
What are the 3 signals involved in B cell activation?
1-Antibody crosslinking-activation
2-Co-receptor signaling- survival and proliferation
3-Cytokine-differentiation
The clustering of antigen receptors allows what?
Receptor-associated kinases to phosphorylate ITAMs. Syk binds to the doubly phosphorylated ITAM to be activated
What are the 3 components of the B cell co-receptor complex?
1-Complemment receptor 2 (CR2) (Binds iC3b and C3d)
2-CD19 (signaling arm)
3-CD81 (localizes complex within plasma membrane
What are the 4 main sources of co signaling?
1-B-cell co-receptor complex
2-TLRs
3-CD40
4-Cytokines
Which cells are stromal cells, cause B cell development and activation, have complement receptors, accumulate antigens on their surface to display to B cells but lack phagocytic capacity?
Follicular dendritic cells
How and where are cognate pairs formed?
Antigen-activated B cells present antigen to effector Tfh cells at the follicle boundary between the primary follicle and T cell area
ICAM binds LFA-1 to loosely bind a T cell to a B cell. What B cell surface protein then induces survival and proliferation?
CD40
*B cell then differentiates into plasma or memory cell. Can also undergo isotype switching in the germinal center
What are the two stages (and locations) of B cell differentiation into plasma cells?
1-Primary focus (medullary cords)
2-Secondary focus (primary follicle)
Proliferation of IgM secreting B cells for several days driven by IL-5 and IL-6 is typical of what stage of B cell differentiation to plasma cells?
Primary focus
B cells rapidly dividing every 6 hours to form centroblasts and germinal centers driven by IL-6, IL-15, 8D6 and BAFF are typical of what stage of B cell differentiation into plasma cells?
Secondary focus
Which cells make up germinal center dark zones, are the source of proliferating B cells, do not express surface immunoglobulin, undergo somatic hypermutation and class switching?
Centroblasts
*Also Create centrocytes
Which cells form the light zone, divide slowly, express surface immunoglobulin, cannot class switch or hyper mutate, interact with and are selected by follicular dendritic cells and are programmed to die?
Centrocytes
What are the 3 zones of a germinal center?
1-Dark zone (centroblasts)
2-Light zone (centrocytes)
3-Mantle zone
*T cell area is near by
FDC binding to high affinity centrocytes leads to what?
-Tfh cell recruitment which sends the survival signal and causes centricity differentiation
Which cytokine leads to centrocyte differentiation into plasma cells?
IL-10
Which cytokine leads to centrocyte differentiation into memory B cells?
IL-4
What are the 4 broad effector functions of antibodies?
1-Virus and toxin neutralization
2-Opsonization (phagocytosis)
3-Complement fixation and formation of MAC complex
4-Antibody-dependent cell-mediated cytotoxicity
Which three Antibody isotypes serve to protect internal tissues?
IgM, IgG, IgA
Which antibody isotype is found on mucosal surfaces mainly?
IgA
Which antibody isotype aids in parasite immunity?
IgE
FcyRI is an example of a high affinity receptor for IgG1 and IgG3 and facilitates signaling, transport, internalization and is found as a monomer or dimer. It is also part of what broader group that facilitate antibody functions?
Fc Receptors
*bind Fc region of the antibody
What are three take home points about Fc receptors?
1-Can stimulate as well as activate
2-Are expressed on most leukocytes
3- Form only for IgG, IgE and IgA
IgG is transported from the _______ to the _______ which is facilitated by ________
blood stream, tissue, Fc receptors
PIgR is a receptor that facilitates what?
Transcytosis of IgA to protect mucosal surfaces
Agglutinized antigens are cleared by what?
Erythrocytes binding them via CR1. They are carried to liver or spleen to be taken up by macrophage
Which antibody makes mast cells, basophils and eosinophils competent?
IgE
Which two antibodies initiate the complement classical pathway?
IgM and IgG
_______ is passed during gestation for passive immunity and ______ is passed during breast feeding to protect infant mucosal surfaces
IgG, IgA
