Monoclonal antibodies which specifically bind human CD23, the low affinity receptor for IgE (FceRII/CD23), and contain either a human gamma-1 or human gamma-3 constant domain, are disclosed. The antibodies are useful for modulating or inhibiting induced IgE expression. Accordingly, they have practical utility in the treatment or prophylaxis of disease conditions wherein inhibition of induced IgE production is therapeutically desirable, including allergic conditions, autoimmune diseases and inflammatory diseases.