An ultrastructural study of in vivo interactions between lymphocytes and endothelial cells in the pathogenesis of the vascular leak syndrome induced by interleukin-2.

Lymphokine-activated killer (LAK) cells play a major role in the induction of the vascular leak syndrome (VLS). To understand the mechanism of this syndrome, the authors examined light and electron microscopic alterations in the lung, liver, spleen, kidney, and heart of mice in which VLS was produced by the administration of interleukin-2 (IL-2) (seven injections of 600,000 IU each for a period of 4 days). The results of these studies disclosed that considerable damage had been done to the endothelial cells that consisted of cytoplasmic edema, vacuoles, and myelin figures; in addition, there were frequent sites of transendothelial passage of lymphoid cells, probably IL-2-activated cells, that penetrated through their cytoplasm by means of "temporary migration pores" and accumulated in the perivascular spaces. The results of this study indicate that a direct in vivo interaction between IL-2-activated cells (probably LAK cells) and endothelium results in cytotoxicity to endothelial cells.