Heterogeneity of Rabbit Homologous Skin Sensitizing Antibodies: IgE and a New Subclass IgGa

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Abstract
Homologous skin sensitizing antibodies in the rabbit can be differentiated by their requirement for complement in expressing the passive cutaneous anaphylactic reaction as complement dependent (CD) or complement independent (CI). CI antibodies are representative of the IgE class, while the CD antibodies belong to a proposed new subclass of IgG designated IgGa (a = anaphylaxis). The following are characteristics of CI (IgE) antibodies: elution at 0.05 M on DEAE at pH 8.1, migration ahead of 7S in ultracentrifugation, molecular weight 215,000 daltons by Sephadex G-200, fast γ-electrophoretic mobility, isoelectric point, pI = 4.98 (5.68–4.58), 85–95% heat sensitivity, sensitivity to reduction plus alkylation and optimal sensitization period of 1–7 days. In contrast CD (IgGa) antibodies show: elution at 0.01 M on DEAE, 7S in ultracentrifugation, MW 138,000 daltons, slow γ-electrophoretic mobility, pI = 6.90 (8.30–5.70), resistance to heating and to reduction plus alkylation and 1-day optimal SP. CI antibodies could be absorbed by anti-Fab, anti-ε, the homologous antigen and were not absorbed by anti-γ, anti-α, or heterologous antigens. The CD antibodies were absorbed by anti-Fab, anti-γ and not absorbed by anti-ε, anti-α, or heterologous antigens.