Earthworm leukocytes that are not phagocytic and cross-react with several human epitopes can kill human tumor cell lines

Earthworm coelomocytes (leukocytes) effect cytotoxicity at significantly high levels against the NK-sensitive, human tumor cell line, K562, and the NK-resistant targets (U937, BSM, GEM). By cytofluorimetric analyses using mouse anti-human monoclonal antibodies and by morphological evaluations, two types of coelomocytes were identified: (1) small (8-11 mu m) electron-dense cells (SC): CD11a+, CD45RA+, CD45RO+, CDw49b+, CD54+, beta(2)-m+, and Thy-1+; (2) large (12-15 mu m) electron-lucent cells (LC) that are negative for these markers. Both cell types were negative for other CD and MHC class I and class II markers. SC were active during recognition, rapidly binding to targets; LC were phagocytic. Release of Cr-51 revealed rapid, significant, and equal levels of killing at 4 degrees, 20 degrees, and 37 degrees C. We propose that primitive NK-like activity appeared early in evolution. (C) 1996 Academic Press, Inc.