IgM of the chicken (.apprx. 3% of serum IgM), clawed toad (12%) and carp (13%) bind to protein A-Sepharose. A monomeric Ig with 4 domain H chains from chicken serum is also bound (30% of bound Ig). Protein A-Sepharose can be used for isolation of IgM of the clawed toad and carp directly from the serum.