B Cells Flashcards
Name for all proteins which structurally resemble antibodies
Immunoglobulin
Proteins made by lymphocytes and plasma cells that specifically react with antigens
Antibodies
Type of antigen that causes an immune response
Immunogen
Any compound that elicits an immune response
Antigen
Do antigens that are proteins and polysaccharides induce a strong or weak immune response?
Strong
Do antigens that are lipids and nucleic acids induce a strong or weak immune response?
Weak
Chemical structure of an antigen that is directly recognized
Epitope
Does an antigen with different epitopes get recognizes more slowly or quickly than an antigen with repeated single epitope?
More rapidly (allows multiple different targets for recognition
Antibody chains
2 identical heavy and light chains; both contain variable and constant regions
Antigens bind to this location on antibody
Fragment antigen-binding (FAb) region (variable region)
Constant region of antibody that tells the host how to handle the Ag:Ab complex
For interaction with host
Fragment crystallizable (Fc) region (constant region)
Class of immunoglobulins that exists as a dimer in mucosal immunity
IgA
Class of immunoglobulins that has trace amounts in the serum, is a monomer, and functions in naive B cell antigen receptor
IgD
Class of immunoglobulins that has small amounts in serum and is involved in immediate hypersensitivity (mast cell activation)
IgE
Class of immunoglobulins that has 4 different types, has high levels in serum and a long half-life.
Involved in defense against microbes in all tissues (neutralization, opsonization, complement, Ab-dependent cellular cytotoxicity), neonatal immunity
IgG
Class of immunoglobulins that is present in the serum, part of naive B cell antigen receptor (monomeric form), defense against microbes (complement, neutralization), and can have a pentameric structure
IgM
Molecule that links secreted IgM to form a pentamer
J chain
Function of the J chain
Links secreted IgM to form a pentamer
Does IgM have high or low avidity?
High due to pentamer structure
Does IgM have high or low affinity?
Low
B cells are produced here
Bone marrow
The association of lymphoid progenitor cells with bone marrow stromal cells is mediated by these types of molecule
Cellular adhesion molecules (specifically the integrin VLA-4 and adhesion molecule VCAM-1)
Expressed on B cells and binds to the membrane-bound stem cell factor (a growth factor)
Kit
Kit is expressed on these cells
B cells
Production of this cytokine by bone marrow stromal cells stimulates B cell growth and proliferation
IL-7
IL-7 stimulates this
Stimulates B cell growth and proliferation
Is the heavy or light chain rearranged first in B cell rearrangement?
Heavy chain
Order of genes rearranged in B cell heavy chain
D to J, then V to DJ
Order of genes rearranged in B cell light chain
V to J
Number of constant genes on the heavy chain that define the antibody isotype that is being produced by the cell
9
Default constant genes for all B cells
Cμ (IgM) and Cδ (IgD)
B cells express these immunoglobulins at cell surface during development
IgM and IgD
Process of germline rearrangement that ensures gene segments are joined in the correct orientation
12/23 rule
Each V, D, or J segment is flanked by recombination signal sequences with either 12 or 23 base pair segments
The 12/23 rule ensures this
Ensures gene segments are joined in the correct orientation during lymphocyte germline rearrangement
Sequences which flank each V, D, or J segment and exist as nonamer and heptamer separated by either a 12 or 23 base pair segment
Recombination signal sequences (RSS)
Molecules which bind to the 12 and 23 base pair spacers of recombination signal sequences, bringing two heptamer sequences into close proximity through formation of a hairpin that contains the DNA segments that are being removed (V, D, or J)
Recombinase-activating genes (RAG-1 and RAG-2)
Recombinase-activating genes (RAG-1 and RAG-2) are involved in this process
Germline rearrangement; bind RSSs and aid in removal of sequences between V/D/J segments
Most abundant antibody in the blood
IgG
Enzyme that joins chromosomal DNA together to form the coding joint after VDJ rearrangement and removal of RSSs
Contributes to the diversity of Ab repertoire during the formation of the coding joint by adding N-nucleotides
Terminal deoxynucleotidal transferase (TdT)
Palindromic nucleotides, but they are not complementary to each other and cannot join together
P-nucleotides
Antibody that passes through the placenta
IgG
Antibody found in milk by lactation
IgA
Are rearrangements random?
Yes; occur throughout life
What makes up the pre-B cell receptor after heavy chain rearrangement?
Rearranged heavy chain, Surrogate light chain, and Iga and IgB (disulfide-linked signaling molecules)
Surrogate light chain is a required component of this
Pre-B cell receptor
Describes the strength of binding at a single site
Affinity
Describes the strength associated with binding multiple sites
Avidity
Process of encoding Ig genes from a single chromosome per cell, instead of both
Makes homogenous BCRs with high-avidity binding
Allelic exlcusion
These 2 immunoglobulins are co-expressed at the cell surface of mature, naive B cells by alternative splicing
IgM and IgD
Terminal deoxynucleotidal transferase (TdT) is involved in this process
Germline rearrangement 12/23 rule; joins chromosomal DNA together to form coding joint between V/D/J segments
Contributes to Ab diversity
If an immature B cell reacts with self antigen, it undergoes receptor editing via rearrangement of this locus
Light chain
Process where elimination of self reactive B cells occurs before they leave the bone marrow
Central tolerance
Process where elimination of self reactive B cells occurs after they leave the bone marrow
Peripheral tolerance (Anergy)
Chemokine that interacts with its receptor (CCR7) on B cells to attract B cells to the high endothelial venules and into lymph nodes
CCL21
Receptor on B cells for CCL21
CCR7
CCL21 interacts with its receptor CCR7, which is on these cells
B cells
Function of CCL21
Attracts B cells to high endothelial venules for movement into lymph nodes
Two TNF-alpha family members that drive the maturation of immature B cells
B cell activating factor (BAFF) and Lymphotoxin (LT)
TNF-alpha family member that is produced by follicular dendritic cells (FDCs) and binds it receptor on B cells to promote survival and maturation of the B cell
B cell activating factor (BAFF)
B cell activating factor (BAFF) is produced by these cells
Follicular dendritic cells
TNF-alpha family member that is produced by B cells and binds its receptor on FDCs to preserve integrity of the FDC network
Lymphotoxin (LT)
Lymphotoxin is produced by these cells
B cells
Cross-linking of antigen induces signaling within the B cells that is mediated by these signaling components of the BCR (Ig alpha and beta)
Immunoreceptor tyrosine-based activation motif (ITAM)
Signaling components of the BCR
Ig alpha and beta