Meeting Abstract
When foreign materials, such as bacteria, enter the hemocoel of the American lobster, a rapid immune response is initiated. Following acute bacterial exposure, most bacterial cells are cleared from the circulating hemolymph within 30 min, concurrent with a precipitous drop in the number of circulating hemocytes. Previous studies suggest that, in the presence of foreign material, hemocytes produce adhesion proteins that allow them to bind to the foreign material, as well as to other hemocytes, forming tight clusters referred to as nodules, which could explain their disappearance from the circulating hemolymph. In our experiments, fluorescence microscopy was used to observe, in vitro, hemocyte aggregation in lobster hemolymph in response to acute bacterial exposure. We used Vibrio campbellii, bioengineered to express green fluorescent protein (GFP), which allowed us to better-visualize the interaction between hemocytes and bacterial cells. Hemocyte responses were viewed in real-time using time-lapse videography. Images were taken at five second intervals over ten minutes and showed that hemocyte aggregates began to form within one minute following the introduction of V.campbellii into a hemolymph sample. Bacterial cells were seen to be enclosed in hemocyte aggregates within minutes after initial exposure to Vibrio. Our experiments suggest an apparent relationship between hemocyte response to bacteria and the hemolymph clotting mechanism.
