With the exception of IgM, these Ig heavy chain isotypes appear to be unique to cartilaginous fish and are designated IgW (also called IgX or IgNARC) and IgNAR ('immunoglobulin new antigen receptor').
With the exception of μ, these Ig heavy chain isotypes appear to be unique to cartilaginous fish. The resulting antibodies are designated IgW (also called IgX or IgNARC) and IgNAR ('immunoglobulin new antigen receptor').