Diversity of methods used for characterization of molluscan hemocytes

Hemocytes are the main immune cells of invertebrates; therefore they can be found in molluscs, too. They differ both in morphology and function. The two generally accep- ted morphological types, granulocytes and hyalinocytes, vary in the level of phagocy- tosis and encapsulation, production of reactive oxygen species and nitrogen oxide, and presence of some enzymes. There is an array of methods by means of which hemocy- tes can be characterized. Microscopy serves particularly for study of morphology. An- tigens localized on the surface can be determined by monoclonal antibodies or lectin probes. Hemocytes can be divided on the basis of cell size and granularity using gra- dient centrifugation or flow cytometry. Production of nitrogen oxide and reactive oxy- gen species is monitored by adding appropriate substrate which changes its proper- ties after reaction with the radical. It may become fluorescent, change absorbance of the solution or form a visible precipitate. Another possibility is the use of chemilu- miniscence. The objective of hemocyte research is to explain mollusc-pathogen inter- action.