Immunoglobulin
- Pronunciation
- /im-YOO-noh-GLOB-yoo-lin/
- Category
- Physiology
- Singular
- immunoglobulin
- Plural
- immunoglobulins
Definition
A large, Y-shaped glycoprotein produced by B lymphocytes and plasma that specifically recognizes and binds to antigens, thereby mediating humoral . Immunoglobulins function by neutralizing , opsonizing particles for , activating complement cascades, or triggering antibody-dependent cellular cytotoxicity. The basic structural unit consists of two identical heavy chains and two identical light chains linked by disulfide bonds, with variable regions at the tips of the arms forming the antigen-binding sites (paratopes). Five major classes (IgA, IgD, IgE, IgG, IgM) differ in heavy-chain composition, half-life, tissue distribution, and effector functions.
Etymology
From Latin immunis (exempt, protected) + globulus (small sphere), referring to the globular protein structure and immune function.
Example
In medical entomology, IgE-mediated hypersensitivity is the immunological basis for anaphylaxis following hymenopteran stings; venom-specific IgE binds to mast FcεRI receptors, triggering degranulation upon re-exposure. IgG responses to Plasmodium sporozoite surface proteins (CSP, TRAP) are correlates of protection in vaccine development, while -induced modulation of IgG and IgM responses facilitates transmission.
Synonyms
- antibody
- gamma globulin
Related Terms
- antigen
- epitope
- paratope
- B lymphocyte
- plasma cell
- humoral immunity
- complement system
- opsonization
- hypersensitivity
- anaphylaxis
- venom immunology
- vector-borne disease
Usage Notes
In entomological and ecological contexts, immunoglobulin is preferred over 'antibody' when emphasizing structural classes or molecular mechanisms; 'antibody' is more common in clinical and field descriptions of immune responses. IgE is specifically associated with type I hypersensitivity reactions to venoms and salivary proteins. Do not confuse immunoglobulin superfamily (IgSF) -adhesion molecules with secreted antibodies. The term 'gamma globulin' properly refers only to IgG-rich serum fractions, not all immunoglobulin classes.