Concept
Antibody isotypes
IgG, IgM, IgA, IgE, IgD and their roles
EYE-suh-types
High-yield clue
IgM is the first (primary-response, pentamer) and IgG is the most abundant and the only isotype that crosses the placenta.
Overview
The five immunoglobulin classes defined by their heavy-chain constant region: IgG, IgM, IgA, IgE, and IgD, each with distinct structure and function. High-yield coursework links each isotype to a signature role.
Classification
- Immunology concept
- Five heavy-chain classes
- Monomer/dimer/pentamer structures
Lab & identification clues
- IgM pentamer is the strongest complement activator
- IgA dimer with secretory component dominates mucosal secretions
- IgE binds mast cells (allergy/helminth vocabulary); IgD marks naive B cells
Associations
- IgM rise signals recent/primary exposure vocabulary
- IgG mediates opsonization and neutralization
- Serology contrasts IgM vs IgG as timing markers
Commonly confused with
- IgG vs IgM timing
- IgA vs IgE roles
Your notes
Original microbiology concept summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC/WHO topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment selection, infection-control instructions, or specimen-handling guidance.