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Immunology 5: B cells and Antibodies
Terms in this set (81)
__________ domains found in many proteins in immune and nervous systems, and in cell-cell interactions.
what are the two chains in an antibody molecule?
two identical heavy chains and two identical light chains
What is each heavy chain made up of?
one variable region (VH) and three constant regions (CH1, CH2, CH3)
What is each light chain composed of?
one variable domain (VL) and one constant domain (CL)
What are the two functionally distinct fragments that an antibody molecule can be cleaved into?
Fab and FC
Fab is the fragment _________
antigen binding region
Fc is the fragment for _______
Antibodies bind antigen whose surfaces are_________
complementary to that of the antibody.
True or False: Covalent bonds occur between antigens and antibodies.
False: Covalent bonds do NOT occur
There are at least 1011 different antibody specificities available in each individual, each with unique ___________
amino acid sequences in their antigen-combining sites.
Human antibody monomer is of ________
what is the first antibody to be produced in a humoral immune response(low affinity but high avidity)?
IgM occurs as pentamers with _______
J chains, mostly in blood
IgM is important in ________
the rapid control of bacterial infections
What is the most effective at activating complement?
Which human antibody monomer is the most abundant and long-lived in serum?
Which human antibody monomer is responsible for penetrating extravascular body spaces, neutralizing bacterial toxins and viruses and opsonizes pathogens to enhance their phagocytosis?
IgG sensitizes for _______
killing by NK cells
IgG activates the ______ complement pathway.
What antibody monomer crosses the placenta to protect fetuses?
What is the principal isotype in secretions, the most important being the mucus epithelium of the intestinal and respiratory tracts and breast milk?
IgA occurs in ________
blood and extravascular sites as a monomer
Which antibody monomer forms dimers with J chains?
IgA forms dimers with J chains. These bind to_____________
poly-Ig receptors on epithelial cells,
undergo transcytosis across the cytoplasm and are secreted into external body fluids bound to the secretory component called S.
IgA acts mainly as a _______
neutralizing antibody on epithelial surfaces.
(There are two subtypes IgA1 and IgA2.)
Which human antibody monomer is a cell surface receptor involved in lymphocyte activation and suppression?
___________ is coexpressed with __________ on the surface of a mature B cell.
IgD ; IgM
IgD is secreted in ____________
upper respiratory mucosa
True or False: IgE is always a monomer.
Which human antibody monomer binds with high affinity on mast cells found just beneath the skin and mucosa and
along blood vessels in connective tissue?
in IgE, Antigen binding triggers ______________. This occurs during allergic reactions and is important in host resistance to parasite infections
degranulation and the release of inflammatory mediators.
Which antibody monomer occurs in a very low concentration in serum and is responsible for sensitizing for the killing by eosinophils?
What happens during VDJ joining?
One of the DNA segments of V, D, and J is selected, joined through DNA recombination/rearrangement. DJ are joined first, and then V is brought to DJ.
Class switching enables the same assembled ____________
VH exon to be associated with different CH genes during an immune response
Every B cell begins by expressing _______ with a particular VH exon on its cell surface.
A mature or naïve B cell expresses both IgM and IgD on its cell-surface. This coexpression is regulated by _______.
RNA processing or splicing.
Later in the immune response, after exposure to antigen, the assembled VH exon may be expressed in one of IgG, IgA, and IgE isotypes, which is called ______.
What is the molecular basis for isotope switching?
Exposure of activated B cells to IL-4 induces _______ production, while TGF-β
IgE ; IgA
What is papain responsible for?
Cleaving IgG into functionally distinct fragments
What occurs at the junctions of the recombining V, D, and J segments?
exonuclease may remove nucleotides, terminal deoxynucleotidyl transferase (TdT) adds nucleotides, and overhanging DNA sequences may be filled in
Each B cell produces ____________
immunoglobulin of a single specificity
What are the two separate functions of the antibody molecule?
1) to bind specifically to molecules from the antigen that elicit the immune response
2) to recruit other cells and molecules to destroy the pathogen once the antibody is bound to it
_______ is the most abundant immunoglobulin in plasma
Immunoglobulins of all heavy-chain isotypes can be produced either in _____
secreted form or as a membrane-bound receptor
The transition from membrane to secreted heavy chain occurs at the level of __________.
Each B cell expresses only one of the two parental alleles of immunoglobulin (Ig) antigen receptor. This phenomenon is called ____________
Allelic exclusion is important for each B cell clone to ___________.
maintain a single antigenic specificity.
A single specificity is maintained because __________
only one of the two parental alleles of Ig is expressed by each B cell clone.
True or False: Allelic exclusion does not apply to TCR beta chain.
FALSE: it does apply to TRC beta chain
There are _________ possible combinations of heavy and light chain genes that can be combined to form one antibody.
Only one of the eight possible combinations can exist at any one time and the other seven are excluded through a combination of ____________
allelic and isotypic exclusion.
Because only one gene can be active in any one B-cell so not only does there have to be an allelic exclusion (either the one from the mother or father) but one of the two genes from that parent needs to be excluded (either the kappa or lambda gene from one parent). This latter is referred to as __________.
Naïve, mature B cell expresses IgM and IgD when exiting BM. It circulates through lymph nodes. If it meets its antigen, it __________(7 steps)
starts to secrete IgM, interacts with activated Th cells, forms germinal centers, undergoes class-switching, produces high affinity Ab, then becomes a plasma cell or a memory cell.
RAG-1 and RAG-2 are __________
recombination activating genes
DNA PK is a ________
Artemis is a __________
Failure of any of the enzymes such as RAG-1/RAG-2, Ku70/Ku80, DNA-PK, or Artemis result in a ____________
in lymphocyte development and
in severe combined immune deficiency (SCID)
What is negative selection?
When self-reactive BCR-bound B cells are removed and receptor editing of the light chain occurs
Describe the development and maturation of B cells:
Stem cell--> pro B --> pre-B--> immature B--> mature B
what else does allelic exclusion also apply to?
TCR beta chain
What are the two signals needed for B cell actuation of thymus dependent antigens?
the first signal is from BCR crosslinked by antigen binding, which results in the B cell proliferating and secreting low levels of IgM; the second signal is CD40L from the helper T cells.
What are the two signals needed for B cell actuation of thymus independent antigens?
both signals are from the antigens themselves. These antigens include bacterial polysaccharides which can induce IgM antibody production.
What else can provide the second signal in thymus independent antigens?
B and T cells are _________ activated by antigen before interacting together.
B and T cells form an __________ of activated B cells in which early antibody responses occur.
extra follicular focus
The extrsfollicular focus is followed by the formation of ___________ in which stronger more effective antibody responses develop,
B cells within germinal centers interacting with __________ undergoing class switching and V-region somatic mutation.
follicular helper T cells
Antigen is presented to B cells by_________in the germinal centers.
follicular dendritic cells
The B cells with mutations in the V regions of their Ig genes that improve affinity for antigen are selected. This results in antibodies having ________
higher affinities for antigen.
somatic (hyper)mutation (does/ does not) occur in T-cells.
During a germinal center reaction, some Ig-secreting plasma cells migrate to the _________ and continue to produce antibody even after antigen is eliminated.
Memory B cells develop in the __________
germinal centers and enter the circulation.
Antigen-antibody complexes ( down/up ) regulate B cell activation
Describe how the neutralization of bacteria blocks the infection
first bacteria colonies on surfaces by using bacterial adhesion, then some species of bacteria become internalized and propagate in internal vesicles, and finally the antibodies against adhesions blocks colonization and uptake
Describe the role of antibodies in opsonization: The opsonization of microbe by _______.
Describe the role of antibodies in opsonization: Binding of opsonized microbes to ________
phagocyte Fc receptors
Describe the role of antibodies in opsonization: The Fc receptor signals _____
Describe the role of antibodies in opsonization: What occurs after the Fc receptor signals activate phagocyte?
phagocytosis of the microbe
Describe the role of antibodies in opsonization: Phagocytosis of the microbe results in ________
killing of ingested microbe
_________ complex formation activates the classical complement pathway.
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