Provided is a method of making a soluble, monoclonal agnathan antigen specific polypeptide comprising a. isolating a cDNA clone encoding an agnathan antigen specific polypeptide, wherein the agnathan antigen specific polypeptide comprises an N-terminal leucine rich repeat (LRRNT), one or more leucine rich repeats (LRRs), a C-terminal leucine rich repeat (LRRCT), and a connecting peptide, wherein the connecting peptide comprises an alpha helix b. transfecting a cell in culture medium with the cDNA clone of step (a) and c. isolating the agnathan antigen specific polypeptide from the culture medium.