AUTOGENEIC BUT NOT ALLOGENEIC EARTHWORM EFFECTOR CELOMOCYTES KILL THE MAMMALIAN TUMOR-CELL TARGET K562

Earthworm coelomocytes have been used as effector cells against the human tumor target, K562. To first assess the viability of effecters, incorporation of [H-3]-thymidine was tested and was higher in autogeneic (A double left right arrow A, self) than in allogeneic (A double left right arrow B, nonself) coelomocytes, A double left right arrow A showed significantly greater numbers in S, G2, or M phases than A double left right arrow B coelomocytes. When A double left right arrow A or A double left right arrow B were cultured, no significant cell killing occurred in either, as measured in a 4-hr Cr-51 release assay, A double left right arrow A but not A double left right arrow B killed K562 target cells, Cytotoxicity was dependent upon membrane binding between small, electron-dense coelomocytes and targets; it was enhanced by adding PHA. The heat labile supernatant from A double left right arrow A but not from A double left right arrow B killed K562 targets after cultivation for 10 min at 22 degrees C, but not immediately after washing, Recognition of, binding to, and killing of foreign cells in a natural killer cell-like reaction may reflect natural immunity in earthworms.