CYTOTOXIC REACTION IN ALLOGENEIC MIXTURES OF ECHINOID PHAGOCYTES

Echinoid phagocytes recognize allogeneic and xenogeneic echinoid cells in vitro. This is demonstrated by the occurrence of a cytotoxic reaction after 20 h when phagocytes from different animals are cultured together. Within the species about 70% of different cell combinations gave cytotoxicity, while the frequency of reactivity increased to more than 90% when cells from different species were mixed. Target cells detach and disintegrate rapidly into small fragments. Most target cells seem to be killed between 20 and 36 h. Formation of syncytia is to some extent inhibited prior to the cytotoxic reaction. No cell division occurs during normal cell culture or during the cytotoxic events in vitro. The reaction is contact-dependent, bilateral and is often very strong. In most cases cytotoxicity levels of 20-40% were noted according to 51Cr-release assays. This together with the morphological datas implies that there is a very high proportion of reactive cells in any given allogeneic or xenogeneic cell combination. The mixed phagocyte reaction was not affected by presence of other coelomic cell types. The invertebrate phagocytic cell is probably also the effector cell during graft rejection and may represent the common ancestor of the vertebrate macrophage and lymphocyte. © 1979.