Abstract
Mice treated with sea star factor (SSF), a protein extracted from sea star coelomocytes, became highly susceptible to infection with a normally sublethal dose of Listeria monocytogenes. This was in contrast to the expected result of increased resistance originally postulated because of the macrophage-activating properties of SSF. Enhanced susceptibility was seen when SSF was given from 96 h before to 48 h after infection with Listeria. Mice pretreated with SSF failed to develop immunity to Listeria when given a dose of organisms capable of immunizing nontreated mice. Treatment of immune mice with SSF did not alter their immune status. In addition, incubation of immune lymphocytes with SSF in vitro did not alter their ability to adoptively transfer immunity to normal recipients. Immune lymphocytes treated with SSF and then incubated with anti-SSF and C did, however, lose the ability to transfer immunity. These results suggest that SSF enhances infection by binding to T lymphocytes, inhibiting their replication upon contact with Listeria antigen and thus preventing the generation of a population of sensitized lymphocytes capable of effecting anti-Listeria immunity.