Isotype-Specific Immunoglobulin Binding Factors of IgA and IgE

Growing evidence has shown the importance of Fc receptors (FcRs) and immunoglobulin binding factors (IBFs) specific for various immunoglobulin classes in human as well as murine immune systems (1–7). IBFs for IgA (8–13) and IgE (14–18) are particularly important because of the clinical diseases involving the abnormalities of these systems. In selective IgA deficiency and IgA nephropathy, FcR/IBF for IgA is altered (19). In atopic as well as non-atopic hyper-IgE syndromes, expression of the FcR for IgE (FceR) is up-regulated (3,4,20).