Production of interleukin-1 in a South American opossum (Monodelphis domestica).

A homologous thymocyte costimulatory assay using thymocytes from a South American opossum (Monodelphis domestica) detected and measured interleukin-1 (IL-1). Opossum IL-1 was obtained from lipopolysaccharide-stimulated macrophage and skin cultures and its molecular weight was determined to be 15,000 to 17,000. Opossum IL-1 did not stimulate proliferation of murine thymocytes; conversely, neither human nor murine IL-1 stimulated opossum thymocytes. Anti-human IL-1 antibodies were also not reactive with opossum IL-1. These observations indicate that there is no serological and functional crossreactivity between the opossum (marsupial mammals) and human and mouse (eutherian mammals) in an IL-1/thymocyte system. This is unusual because such crossreactivity occurs between rodents and distant, nonmammalian species. M. domestica has been used in our laboratory as a model for photobiological research; studies on IL-1 may provide insight into the relationship of immunosuppression and tumorigenesis induced by ultraviolet radiation.