INVERTEBRATE IMMUNOCYTES - RELATIONSHIP BETWEEN PHAGOCYTOSIS AND NITRIC-OXIDE PRODUCTION

This report demonstrates the presence of the immunoreactive enzyme nitric oxide (NO) synthase in the molluscan hemocytes of Viviparus ater. Bacterial elimination by the hemocytes occurs through phagocytosis and the nitric oxide (NO) system, These processes are correlated, and the hemocytes activate phagocytosis before the NO defence response. This behaviour could be explained by the fact that, as in vertebrate macrophages, NO synthase can also be induced in invertebrate hemocytes, Indeed, in the bacteria-activated hemocytes there is an increase of NO synthase in comparison to controls, Moreover, the same behaviour is also seen in the NADPH diaphorase activity, These findings suggest a pivotal role of the NO system in defence mechanisms, and indicate that, as with phagocytosis, this system developed very early in the course of evolution.