The characteristics of rhuIL-4 induced cytotoxicity was detected in vitro by using ￣（51）Cr release assay and the anti-tumor activity of rhuIL-4 induced killer cell was evaluated in vivo by using a human tumor model in nude mice. huIL-4 can induce LAK activity from peripheral blood lymphocytes （PBMC） stimulated with phytohemagglutinin （PHA）. Compared with the LAK activity induced by rhuIL-2

the cytotoxicity of the killer cells induced by rhuIL-4 to K562 and Raji cells was lower

but that to TBL-E

a human lymphoid leukernia cell line established in our laboratory

and PHA-activated blast cells （PHA-blasts） was of similar magnitude. In the cytotoxicity assay using PHA-blasts

the addition of PHA increased the IL-4-induced killer cell cytotoxicity by 131%

but had no effect on IL-2-induced killer cell cytotoxicity. This implies that IL-4 mainly induces CTL-like activity

while IL-2 mainly induces NK-like activity. An experimental human tumor model in nude mice was established by injection of TBL-E human leukemia cells. The anti-tumor activity of rhuIL-4 was evaluated by injection of human LAK cells induced from PHA-blasts by rhuIL-2+rhuIL-4 and human cytokines into tumor-bearing nude mice. The results showed that human LAK cells effectively inhibit the tumorigenicity of TBL-E cells in nude mice with an inhibition rate of 61 %. The antitumor effect of rhuIL-2 was better than that of rIL-4

and the antitumor effect of rhuIL-2+rhuIL-4 was similar to that of rhuIL-2

though the former delayed the occurence of tumors. Our data imply the potential application of human IL-4 in clinic

and provide an animal model to evaluate the anti-tumor activity of human cytokine（s） with species specificity.