Studies were performed to characterize the toxic effects of human rIL-2 in mice and to examine the mechanism of toxicity. Intraperitoneal administration of rIL-2 at doses greater than or equal to 2 X 106 U/kg twice each day for greater than or equal to 4 days led to toxicity in several strains of mice. The toxic effects of rIL-2 included the vascular leak syndrome (manifested by pulmonary edema, pleural effusions, and ascites), elevated hepatic transaminases, hyperbilirubinemia, hypoalbuminemia, pre-renal azotemia, anemia, thrombocytopenia, mild eosinophilia, and death. Marked lymphoid cell infiltration of pulmonary and hepatic vasculature was present in mice suffering from rIL-2 toxicity, and the pleural and ascitic fluids also contained high numbers of mononuclear cells. Mononuclear cells isolated from the pleural fluids and livers of these mice were 74 to 98% Thy-1+, 55 to 83% asialo-GM1+, 29 to 45% Lyt-2+, and less than 10% L3T4+. These cells possessed potent lymphokine-activated killer (LAK)-like activity in that their ability to lyse cells of the NK-resistant P815 mastocytoma line was 10- to 100-fold higher on a per cell basis than splenocytes from the same animals. A correlation was found between the dose level, duration, and frequency of dosing with rIL-2 required to induce pleural effusions and hepatotoxicity and the dosage regimens required to produce the LAK-like cells in the pleural cavities and livers, respectively, of rIL-2-treated mice. Moreover, treatment of mice with anti-asialo-GM1 (anti-ASGM-1) antiserum in vivo at the same time they were receiving toxic doses of rIL-2 abolished or greatly reduced the severity of the vascular leak syndrome and hepatotoxicity and significantly prolonged the survival of the mice. Administration of anti-ASGM-1 to mice receiving toxic doses of rIL-2 resulted in a marked reduction in the LAK-like cytolytic activity of their pleural and liver lymphoid cells and a corresponding reduction in the percentage of ASGM-1+ cells in pulmonary and hepatic lymphoid infiltrates. Nevertheless, the overall extent of pulmonary and hepatic lymphoid infiltration, as well as other consequences of rIL-2 administration, including splenomegaly, hypoalbuminemia, eosinophilia, and thrombocytopenia, were not diminished as a result of anti-ASGM-1 treatment. Additionally, the ability of splenocytes from mice receiving both rIL-2 and anti-ASGM-1 to generate allogeneic cytolytic T cell responses in vitro was not impaired, suggesting that T cell function in these mice was intact. These results suggest that ASGM-1+ lymphoid cells, and possibly LAK cells themselves, play a central role in mediating some (but not all) of the toxic side effects of rIL-2, including the vascular leak syndrome and hepatotoxicity. The mechanism by which such cells cause or contribute to the damage of normal tissue remains to be elucidated.
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Gately et al. (1988) studied this question.