“…There fore, the treatment with PTZ in this report could be designated as mainly therapeutic rather than prophylactic for the groups but not for the individuals. In addition to the prophylactic treatment with such high mo lecular immunomodulators as BCG, OK-432, Poly A:U and neuraminadase-treated leukemia cells [2] or purified mouse inter feron [2,11], several cytotoxic chemicals and their combinations have been reported to be effective against AKR spontaneous leukemia [2,10,17,18]. Cyclophospham ide was found to be one of the most active agents among the low molecular substances [10,17,18] which generally have more ad vantages as therapeutical drugs in com parison to high molecular agents.…”