| Themes > Science > Life Sciences > General Biology > Immunology > Recognition Systems in Immunity > Antigen Recognition: B Cells and Antibodies > Antibody classes |
In mice and humans the different types of antibody are known as IgM, IgG , IgA, IgD, and IgE. Subtypes (subclasses) of certain classes exist both in humans (G1, G2, G3, G4, and A1, A2) and in mice (G1, G2a, G2b and G3). Members of each subclass are said to have the same isotype (M, G1 etc, A1, A2, D, & E) which depends on the structure of the heavy chain used. The respective heavy chain alone is described by greek letters (mu,gamma,alpha,delta, & epsilon). Antibodies of each isotype have different properties in terms of complement fixation and binding to immunoglobulin (Ig) receptors. There are two light chain isotypes (kappa and lambda); one B cell will only ever express one light chain isotype (see below). |
| Some antibody classes form
multimeric structures, pentamers in the case of IgM and dimers or trimers
in the case of IgA. These two isotypes also associate with a small protein
called the joining (J) chain required for stabilisation of the
complexes. Click here to see a picture of IgM |
|
|
