Reactivity of Normal Shark Immunoglobulins with Nitrophenyl Ligands

Abstract

Normal nurse shark and lemon shark sera contain ∼17S and 7S immunoglobulins with anti-dinitrophenyl activity. Specifically purified 17S “anti-DNP” precipitated in gels with DNP-BSA conjugates, bound to DNP-immunoadsorbents (∼60%) but did not give detectable binding by equilibrium dialysis. The 7S “anti-DNP” did not precipitate in gels, nor did it bind radiolabeled hapten and only about 25% bound to DNP-immunoadsorbents. Of special interest was the observation that specifically purified 17S “anti-DNP” also agglutinated sheep erythrocytes. However, the agglutination of sheep erythrocytes could not be inhibited with DNP-OH. Whole nurse shark serum contains agglutinins to both sheep and chicken erythrocytes. Experiments showed that this was not due to heteroligating antibodies. The possibility is raised that many of the shark immunoglobulin molecules have a dual function, that is, as antibody and as a carrier for certain hormones or other small molecules.