B cells Flashcards
Are B-cells part of the humoral or cell-mediated immune response?
humoral response
what do B-cells produce?
Produce immunoglobulins
immunoglobulins that remain on the surface of B cells are known as what?
B-cell surface receptors (BCRs)
immunoglobulins that are secreted are known as ???
antibodies
The following describes B1 or B2 cells?
- Appear early in foetal development
- Comprise 5% of all B cells
- Self-renewing in tissues outside the central lymphoid organs
B1 cells
The following describes B1 or B2 cells?
- AKA “conventional B cells”
- Develop in bone marrow
- Populate blood and lymphoid tissues
- Activated in secondary lymphoid tissues
B2 cells
How are B-cells activated after they leave the bone marrow carrying a unique surface receptor?
Activation occurs when the surface receptor encounters the relevant external antigen which stimulates rapid proliferation of the B-cell and antibody production
What occurs if a naive mature B-cell does not encounter an antigen after leaving the bone marrow carrying a unique surface receptor?
it will undergo apoptosis within a few weeks
differentiation of B-cells results in
- ???
-???
- memory B cells
- Plasma B cells
Step 1 of b-cell development:
B-cells precursors undergo ??? in bone marrow
immunoglobulin gene rearrangement
Step 2 of b-cell development:
B-cells undergo negative selection process in bone marrow whereby immature ??? are removed
B-cells bound to self-cell surface antigens (self-cell reacting B-cells)
Step 3 of B-cell development:
mature B-cells migrate to ???
peripheral lymphoid organs and activate when bound to foreign antigen
Step 4 of B-cell development:
activated B-cells differentiate into ???
plasma and memory cells.
What are B-cell receptors?
Immunoglobulins bound to B-cell surfaces. Comprises 4 polypeptide chains linked by disulphide bonds (2 light and 2 heavy chains). Associated with 2 other chains, Igα and Igβ (disulphide-linked) and involved in cell signalling
B-cell activation Thymus independant pathway:
typically a response to ??? and does NOT require direct contact with T(h) cells but DOES require recognition of PAMPs by ??? on B cells
bacterial endotoxins
pattern recognition receptors
B cell activation Thymus dependant pathway: more common, requires direct contact with ??? and induces antigen-specific antibody response = long-lived plasma & memory B-cells
T-helper cells
TRUE or FALSE: both thymus dependant and independant pathways of B-cell activation require cross-linking of B-cell receptors. If only one BCR binds an antigen = NO activation
TRUE
which subset of B-cells are usually produced from thymus-independant activation? B1 or B2?
B1
Antigens of thymus-DEPENDANT or INDEPENDANt b-cell activation are generally microbial cell wall components or polysaccharides
independant
Do thymus dependant or independantly activated B-cells induce weaker, less specific
antibody responses, are short-lived plasma cells producing IgM, and have no ability to class switching
thymus-independant
the antigens of thymus-dependant activated B-cells are ??? and induce antigen specific antibody responses. Produce long lived plasma B cells and memory B cells
most proteins
Co-stimulatory molecules that are needed for B-cell activation include:
- Signal 1: Antigenic peptide presented by B cell MHC class
II molecules to ???
- Signal 2: B cell CD40 interacts with
- Signal 3: Induces the release of ???(IL-4), that stimulate B cell ???receptors (IL-4R)
- TH cell
- TH cell CD40L
- cytokines
TRUE or FALSE: B and TH cells need to recognize the same antigen for activation (but not necessarily the same epitopes)
TRUE
TRUE or FALSE: Secondary antibody responses (responses to repeated exposure to the same antigen) are faster and more specific than primary antibody responses
TRUE
