The Journal of Immunology, Vol 143, Issue 7 2407-2414, Copyright © 1989 by American Association of Immunologists

ARTICLES

Activated endothelial cells resist lymphokine-activated killer cell- mediated injury. Possible role of induced cytokines in limiting capillary leak during IL-2 therapy

JW Mier, EP Brandon, P Libby, MW Janicka and FR Aronson
Department of Medicine, New England Medical Center, Boston, MA 02111.

We previously demonstrated that IL-2 promotes the adhesion of NK cells to endothelial cells (EC) and that EC are readily lysed by lymphokine- activated killer (LAK) cells in vitro, suggesting that cell mediated endothelial injury may contribute to the capillary leak syndrome observed in patients treated with IL-2. In this investigation, we sought to determine the effects of EC activation on the in vitro susceptibility of EC to LAK cell-mediated cytolysis. Despite increased binding of CD16+ lymphocytes to TNF-activated EC monolayers, prior exposure of EC to any of several IL-2-inducible cytokines including TNF- alpha, IL-1 beta, and IFN-gamma not only failed to render the EC more vulnerable to cytolysis but increased their resistance to LAK cells in 111Indium release cytolysis assays. This decrement in susceptibility to cytolysis resulting from prior exposure to cytokines preceded any detectable increase in HLA class I or II Ag expression. In cold target competition experiments with LAK cell effectors and radiolabeled K562 target cells, TNF-primed EC were no more competitive than unstimulated EC, and in assays with unstimulated PBMC effectors, the addition of unlabeled TNF-activated EC actually increased the cytolysis of the radiolabeled tumor cells. The effects of various cytokines and lymphocyte preparations on EC permeability were also evaluated. In these experiments, saphenous vein EC were cultured on porous filter disks, exposed to cytokines or lymphocytes, and the diffusion of 125I- BSA through the filters was then measured. Exposure to IL-2, IFN-gamma, or TNF-alpha did not increase the diffusion of the BSA through the EC- coated filters, whereas LAK cells markedly increased their permeability. Consistent with the results of the cytolysis assays, pretreatment of the EC with TNF, IL-1, or IFN-gamma diminished the LAK cell-induced increase in BSA diffusion. These results suggest that although circulating IL-2-inducible cytokines such as TNF and IFN-gamma may activate EC in vivo and contribute to lymphocyte margination and lymphopenia, they may not be directly responsible for the IL-2-induced capillary leak syndrome and may actually protect EC from LAK cell- mediated injury.

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