Identification and partial characterization of common seal (Phoca vitulina and grey seal (Haliochoerus grypus) interleukin-6-like activities

Abstract Interleukin-6 (IL-6) is a pleotropic molecule with many important immune modulatory actions. We have investigated the production of biological activity of this cytokine in two species of European seal. IL-6-like activity was detected in supernatants from cultured peripheral blood leucocytes. This IL-6-like activity had an apparent molecular weight of 17–26 kDa, similar to that of human IL-6. IL-6-like activity was also detected in plasma taken from seals with symptoms of systemic infection, but not from apparently healthy seals. Inhibition of this plasma and leucocyte derived activity was accomplished with both rabbit and goat antisera raised against recombinant human IL-6. Further investigation using polymyxin-B showed that this activity was not due to residue LPS present in the supernatants or infected plasmas.