EFFECTS OF LOW-DOSE TOTAL-BODY IRRADIATION (LDTBI) AND RECOMBINANT HUMAN INTERLEUKIN-2 IN MICE

10-16-Week-old female BALB/c mice received low dose total body irradia tion (LDTBI) in one fraction immediately before the beginning of treat ment with recombinant human interleukin-2 (rlL-2). LDTBI prevented in a dose-dependent manner the weight increase of the spleen, liver and l ungs induced by fluid extravasation provoked by rIL-2 injections. It a lso limited the increase of the number of mononuclear cells in the spl een induced after in vivo treatment with rIL-2. Immunofluorescence ana lysis of spleen cells revealed that LDTBI decreased the relative sIgM cell number in spleen, while the relative numbers of Lyt-1+, Thy-1+ a nd L3T4+ cells were increased, indicating that a T and/or NK populatio n, radioresistant to LDTBI, could still proliferate under rIL-2 stimul ation in vivo. Such lymphocytes were capable of in vitro lysis of YAC cells in a 4-hour Cr-51 release assay, as well as lymphokine-activated killer (LAK) cells obtained in mice treated with rIL-2 alone. Thus, L DTBI given prior to rIL-2, yet preserving the cytotoxic capacity of th e LAK cells activated by rIL-2, could prevent the vascular leak syndro me toxicity induced by rIL-2 injection.