Over 30 years age, IgE was discovered to be the antibody isotype mediating immediate hypersensitivity reactions in humans [1].
An IgE isoform differs by the replacement of the 2 C-terminal aminoacids by 8 amino acids including a C-terminal cysteine. This isoform is present in plasma as part of covalent complexes of approximately 300 kDa and 338 kDa [2].
[1] | Coombs R. R. et al. Lancet 1, 1115-1118 (1968). | [2] | Chan L. A. et al. Mol. Immunol. 37, 241-252 (2000). |