Absence of lymphokine-enhanced macrophage migration in vitro in the Australian brush-tailed opossum, Trichosurus vulpecula.

The supernatants from cultures of either opossum or guinea pig splenic lymphocytes, stimulated with phytohaemagglutinin, significantly enhanced the in vitro migration of guinea pig peritoneal macrophages (P greater than 0.001) but not that of opossum peritoneal macrophages. Failure of opossum macrophages to respond to a putative macrophage chemotactic factor might account for the observed paucity of immune granulomas in these animals and help explain the species' susceptibility to tuberculosis.