Characterization of immunoglobulin from the Pacific hagfish, a primitive vertebrate.

Antibodies to group A streptococcal carbohydrate, demonstrable by radioimmunoassay, were elicited in Pacific hagfish, Eptatretus stoutii, after prolonged immunization with whole cell vaccine. This hagfish antibody, isolated by ion-exchange chromatography of immune serum, exhibited a single precipitin line after immunoelectrophoresis against rabbit antiserum to hagfish serum. The isolated antibodies retained high binding activity for the streptococcal carbohydrate, but lacked the natural hemagglutinating activity found in both nonimmune and immune sera. Analysis by gel filtration in neutral and dissociating buffers and by sodium dodecyl sulfate/polyacrylamide gel electrophoresis under nonreducing conditions indicated an intact molecule of molecular weight approximately 160,000 that may be noncovalently associated in a polymer of higher molecular weight. Heavy chains of mobility identical to that of murine mu chains and light chains of mobility significantly slower than murine lambda chains were obtained after sodium dodecyl sulfate gel electrophoresis under reducing conditions. Instability of the tertiary structure of the antibody molecule was indicated by partial dissociation in buffers containing sodium dodecyl sulfate and by dissociation at low concentrations of reducing agent. In contrast to its well-developed system of cell-mediated immunity, only a minimal system of circulating antibody production is evident in this primitive fish. No evidence for divergence of cyclostome lymphocytes into separate T- and B-cell systems has yet been discerned.