Antigen-Antibody Interaction and Immunoglobulins

Vocabulary practice flashcards covering immunogen traits, antibody structure, classes, and immune response kinetics from the Antigen-Antibody Interaction lecture.

Antigen

A substance that reacts specifically with an antibody or sensitized T cells, but may not always be capable of inducing an immune response on its own.

Immunogen

A substance capable of triggering a humoral or cell-mediated immune response.

Immunogenicity

The ability of a substance to induce a humoral and/or cell-mediated immune response.

Autoantigen

An antigen that originates from the same individual host.

Alloantigen

An antigen originating from a different individual of the same species.

Heteroantigen

An antigen originating from a species different from the host.

Heterophile antigen

Hetero-antigens existing in unrelated plants or animals that are identical or closely related in structure, allowing antibodies produced against one to cross-react with the other.

Epitope

The determinant site on an antigen or immunogen that binds specifically to the paratope of an antibody or T lymphocyte receptor.

Paratope

The antigen-binding site on an antibody that specifically binds to the antigenic determinant site (epitope).

Sequential epitope

An epitope consisting of a continuous sequence of amino acids on a single polypeptide chain.

Conformational epitope

An epitope formed by the folding of a polypeptide chain or chains, bringing non-sequential amino acids into close spatial proximity.

Hapten

A tiny non-immunogenic molecule that can react with antibodies, but requires binding to a larger carrier molecule to induce an immune response.

Adjuvant

A substance administered alongside an immunogen that enhances, accelerates, and prolongs the immune response.

Hinge region

The flexible portion of an antibody located between the CH1 and CH2 constant domains, rich in the amino acid proline.

Isotype

Heavy chain structural variations unique to each distinct immunoglobulin class and subclass across all individuals of a species.

Allotype

Minor genetically determined variations in a particular heavy chain class found among different individuals of the same species.

Idiotype

Unique structural variations in the variable regions of immunoglobulin chains specific to a single antibody clone.

IgG

The most abundant serum immunoglobulin class ($70\text{--}75\text{\%}$) that crosses the placenta and predominates in secondary immune responses.

IgM

A pentameric immunoglobulin containing 10 antigen-binding sites, acting as the primary response antibody and found mainly in the intravascular pool.

IgA

An immunoglobulin class predominant in body secretions such as saliva, tears, and mucus, existing as a monomer in serum (IgA 1) and a dimer in secretions (IgA 2).

IgD

An immunoglobulin class expressed on the surface of naive B cells that functions in regulating B-cell differentiation.

IgE

A heat-labile reaginic immunoglobulin that binds to mast cells and plays a major role in allergic reactions and responses to parasitic infections.

Lag phase

The initial phase of the immune response following initial antigen exposure during which no specific antibody is detected in serum.

Monoclonal antibody

An antibody derived from a single parent antibody-producing cell clone, providing uniform specificity.