Analysis of the isotype specificity of three platypus immunoglobulin Fc receptors

The host’s defense against diseases called immunity acts either via innate or adaptive defense mechanisms. Immunoglobulins (Ig’s) are important players in adaptive immunity. They have evolved both structurally and functionally during vertebrate evolution. The Fc region of Igs can interact with specific receptors on the surface of various immune cells; crosslinking of these Fc receptors can trigger a wide array of immune reactions. To trigger such reactions, higher mammals have five different classes of Igs (IgM, IgG, IgA, IgE and IgD) while amphibians, reptiles and birds have four (IgM, IgD, IgA and IgY). Our recent studies have revealed that the early mammals (Platypus) have eight Ig isotypes (IgM, IgD IgO, IgG1, IgG2, IgA1, IgA2 and IgE) and at least four Fc receptors: FcRA, FcRB, FcRC and FcRD. In this study we investigated the specificity of three of these platypus Fc receptors to get a better picture of their isotype specificity.