Antibody Structure and B-Cell Diversity

These flashcards cover key concepts and terms related to antibody structure, generation of B-cell diversity, immunology principles, and related processes.

Antibody

The secreted form of the B cell's receptor for antigen, also called immunoglobulin.

Immunoglobulin (Ig)

The cell-surface (membrane-bound) antigen receptors and the secreted antigen receptors (antibodies) of B cells.

Plasma cells

Effector B lymphocytes that secrete large amounts of antibody.

Clonal selection

The process where B cells recognizing a specific antigen are selected to proliferate and differentiate into plasma cells.

Agammaglobulinemia

A condition caused by the inability of B lymphocytes to make immunoglobulins.

Antibody specificity

The unique property allowing antibodies to bind specifically to one antigen or a small number of similar antigens.

Antibody repertoire

The total number of different specific antibodies that can be made by an individual.

Antigen-binding site

The part of the antibody formed by the amino-terminal ends of the heavy and light chains, responsible for binding the antigen.

Heavy Chain (H chain)

One of the two types of polypeptide chains making up an antibody; consists of two identical heavy chains.

Light Chain (L chain)

The other type of polypeptide chains making up an antibody; consists of two identical light chains.

Variable region (V region)

The amino-terminal region of each heavy and light chain, varies considerably between different antibodies.

Constant region (C region)

The remainder of the heavy and light chains, with a relatively constant amino acid sequence determining effector functions.

Fragment antigen binding (Fab)

A fragment of an antibody that contains the antigen-binding site.

Fragment crystallizable (Fc)

A portion of an antibody that mediates effector functions by binding to receptors on other cells.

Hinge region

A short, flexible section of the polypeptide in certain antibodies that allows movement of the Fab arms.

Immunoglobulin domain

A stable structural unit of antibodies, typically 100-110 amino acids long, forming the immunoglobulin fold.

Complementarity-determining regions (CDRs)

Hypervariable regions in the V regions of heavy and light chains, forming the antigen-binding site.

Somatic recombination

The process in B cells where gene segments are cut and rejoined to create a unique sequence for the immunoglobulin variable region.

Somatic hypermutation

The process that introduces random point mutations into the variable regions of antibody genes after antigen encounter.

Affinity maturation

Selection of B cells with progressively higher affinity for an antigen after somatic hypermutation.

Isotype switching

A change in the constant region of the heavy chain allowing B cells to produce antibodies of a different class.

Polyclonal antibodies

Antibody preparations containing a variety of antibodies specific for different epitopes of an immunizing antigen.

Monoclonal antibodies

Antibodies that are identical and produced by a single clone of B cells.

Hybridoma

The resulting cell formed by fusing a normal B cell with a myeloma cell, which produces monoclonal antibodies.

Chimeric monoclonal antibodies

Antibodies engineered with mouse variable regions and human constant regions to reduce immune response.

Humanized monoclonal antibodies

Antibodies with only the hypervariable loops of mouse antibodies grafted into human immunoglobulin chains.

Hybridoma technology

A method for producing large quantities of monoclonal antibodies by fusing B cells with myeloma cells.

Non-covalent forces

Forces including electrostatic, hydrogen bonds, Van der Waals, and hydrophobic interactions that mediate antibody-antigen binding.

Epitope

The specific part of an antigen that an antibody binds to.

Linear epitope

An epitope formed by successive amino acids in a protein sequence.

Discontinuous epitope

Epitopes formed by amino acids separated in the sequence but brought together in the folded structure of a protein.

V(D)J recombinase

The set of enzymes responsible for cutting and splicing DNA during V(D)J recombination in B cells.

Recombination activating genes (RAG-1 and RAG-2)

Enzymes that cleave and join gene segments in the V(D)J recombination process.

12/23 rule

A restriction ensuring that a 12 bp spacer RSS can only be joined to a 23 bp spacer RSS during gene rearrangement.

P nucleotides

Palindromic DNA sequences created during the repair of cleaved DNA during V(D)J recombination.

N nucleotides

Non-templated nucleotides added randomly to junctions during recombination.

Junctional diversity

Variation introduced at the junctions between V, D, and J gene segments in immunoglobulin genes.

Naive B cells

B cells that have completed development in bone marrow and express surface immunoglobulin but have not encountered antigen.

Allelic exclusion

The mechanism that ensures B cells express only one heavy chain allele and one light chain allele.

B cell receptor complex (BCR)

The functional receptor for antigen on the B cell surface, consisting of membrane-bound immunoglobulin and accessory proteins.

Activation-Induced Deaminase (AID)

An enzyme that converts cytosine to uracil in DNA, crucial for somatic hypermutation and isotype switching.

Antibody affinity

The strength of binding between a single antigen-binding site and its corresponding antigen.

Antibody avidity

The overall strength of binding between an antibody with multiple binding sites and a multivalent antigen.

Fc receptor (FcR)

Receptors found on immune cells that bind to the Fc portion of antibodies, important for opsonization and other immune responses.

C-H gene segments

Gene segments in the heavy chain locus that encode the constant regions of different immunoglobulin isotypes.

Immunogen

An antigen used for immunization to stimulate B cells to produce antibodies.

Flow cytometry

A technology used to analyze cell subpopulations and detect defects or perturbations in tissues.

Antiserum

Blood serum containing antibodies of various specificities.

Antibody concentration

The amount of antibody present in a given volume of serum.

Adjuvants

Substances that enhance the body's immune response to an antigen.

T cell receptor (TCR)

The receptor on T cells that recognizes peptide antigens presented by MHC molecules.

Primary antibody response

The immune response generated after initial exposure to an antigen, resulting in memory B cells and plasmablasts.

Secondary antibody response

An immune response to a subsequent exposure to the same antigen, characterized by quicker and stronger antibody production.

Memory B cells

Long-lived B cells that respond quickly to subsequent exposures to their specific antigen.

T helper cells

A subset of T cells that help coordinate the immune response by providing signals to activate B cells and cytotoxic T cells.

Antigen-presenting cells (APCs)

Cells that process and present antigens to T cells, including dendritic cells, macrophages, and B cells.

Cytokines

Signaling molecules that mediate and regulate immunity and inflammation.

Interferons

A type of cytokine produced in response to viral infections to alert neighboring cells to increase their antiviral defenses.

Chemokines

Cytokines that primarily act to attract immune cells to sites of inflammation or infection.

Regulatory T cells (Tregs)

A subset of T cells that modulate the immune response and help maintain tolerance to self-antigens.

Tumor necrosis factor-alpha (TNF-$ ext{α}$)

A pro-inflammatory cytokine involved in systemic inflammation and the acute phase reaction.

Immunosuppression

The reduction of the activation or efficacy of the immune system, possibly as a treatment for autoimmune diseases.

Vaccination

The administration of a vaccine to stimulate an immune response.