“…ALLOGENEIC RECOGNITION Poikilothermic or ectothermic vertebrates (e.g., fish and amphibians) and other invertebrates possess natural cytotoxic cells (Cammarata et al, 1997;Cooper, 1981;Cooper et al, , 1996Decker et al, 1981;Evans et al, 1992;Evans and Cooper, 1990;Faisal et al, 1989a,b;1990a,b;Franceschi et al, 1991;Ghoneum et al, 1987aGhoneum et al, ,b,1990aGhoneum and Cooper 1987;Kelly et al, 1992;Klempau and Cooper, 1984;Luquet and LeClerc, 1983;Parrinello, 1996;Parrinello et al, 1990;Parrinello and Rindone, 1980;Peddie and Smith, 1993;Sadek et al, 1987a,b;Smith et al, 1988;Söderhä ll et al, 1985;Tyson and Jenkin, 1974;Valembois et al, 1980Valembois et al, , 1982Wittke and Renwrantz, 1984). It is possible to affect the level of cytotoxicity by modifying target cell surfaces, which presumably changes antigenicity.…”