R. Paul Fairman

Nonspecific Cytotoxicity of Recombinant Interleukin-2 Activated Lymphocytes

The administration of interleukin-2 (IL-2) and lymphokine activated killer (LAK) cells to patients with advanced metastatic cancer has yielded encouraging results. The purported ability of LAK cells to be discriminatively tumoricidal, thus sparing normal host tissue, represents a major advance over conventional chemotherapy. However, IL-2 adoptive immunotherapy results in dose-limiting toxicity characterized by weight gain, dyspnea, ascites, and peripheral-pulmonary edema suggestive of a vascular leak syndrome. It is unclear whether the observed toxicity is directly related to IL-2 and/or LAK cells. The authors examined the cytolytic nature of human LAK cells against human endothelial, epithelial, and fibroblast cell lines. Bovine endothelial cells also were studied. Using a 51Cr release assay, the cytolytic potential, time course, and effect of reactive oxygen intermediate inhibitors were studied. LAK cells were uniformly toxic against all cell lines, in contrast to high dose rIL-2 and excipient. Significant cytolysis was observed within 30 minutes and increased over the first 2 hours of LAK cells coming in contact with target cells. Reactive oxygen intermediate inhibitors did not reduce cytolytic activity. The authors thus found human LAK cells to be rapidly cytolytic against a variety of human and bovine cell lines. This cytolysis was independent of reactive oxygen intermediates.

In vivo interleukin-2 activated sheep lung lymph lymphocytes increase ovine vascular endothelial permeability by non-lytic mechanisms

Therapeutic doses of recombinant interleukin-2 (rIL-2) often result in systemic toxicity consistent with increased vascular permeability. rIL-2 activated lymphocytes (IALs) may produce endothelial dysfunction and have cytolytic potential. However, much of the data on IAL cytotoxicity comes from the use of in vitro activated IALs. Alternatively, rIL-2 may enhance permeability directly or via release of various cytokines by host effector cells. The cytotoxicity of in vivo activated lung lymph lymphocytes has been studied in an ovine model of rIL-2 toxicity. The in vivo IALs had no significant endothelial cytolysis at effector to target ratios of 100:1. However, the in vivo IALs increased endothelial monolayer permeability to albumin, dependent on the concentration of IALs. rIL-2 induced no endothelial cytolysis or permeability alterations at doses of 10(5) and 2 x 10(5) U/ml, respectively. These findings suggest that the acute endothelial dysfunction characteristic of the vascular leak syndrome is not due to rIL-2 directly, but is mediated by in vivo IALs via non-cytolytic mechanisms and/or the release of secondary cytokines in response to rIL-2.

The pulmonary hypertension of sclerosing agents is prevented by cyclooxygenase inhibitors.

Sodium morrhuate and sodium tetradecylsulfate are injected during endoscopic scle-rotherapy to control variceal bleeding. When administered to sheep they cause transient pulmonary hypertension and increase protein poor lung lymph flow. To determine the etiology of these alterations, we studied three groups of sheep after establishing acute lung lymph fistulas. In Group 1, indomethacin or ibuprofen was infused. In Group 2, 2.5 cc of sodium morrhuate was injected alone (2A) or after indomethacin or ibuprofen pretreatment (2B.) In Group 3, 2.5 cc of sodium tetradecylsulfate was given intravenously either alone (3A) or after indomethacin or ibuprofen (3B). When sclerosing agents were given alone (Group 2A and 3A) pulmonary artery pressures increased three-fold at 30 seconds postinjection to 37 · 4.4 and 39 · 5.7 mmHg respectively with a slow return to baseline over two hours. Lymph flow increased significantly from 1.3 · 1.5 to 2.7 · 1.5 cc/30 minutes after sodium morrhuate and from 1.2 ± .62 to 2.7 · 1.7 cc/30 mins at 30 minutes after sodium tetradecylsulfate and the lymph/plasma albumin ratio fell. Increased lymph flow persisted through 120 minutes. In those animals receiving a sclerosing agent after indomethacin or ibuprofen (2B and 3B) there was no change in pulmonary artery pressure, lymph flow, lymph plasma albumin ratio, or lung wet weight to dry weight ratios. We conclude that the pulmonary hypertension and increased protein poor lymph flow are mediated by prostaglandins.

Ethchlorvynol-lnduced Pulmonary Edema: A Chronically Instrumented, Awake Sheep Model Mimicking Human Disease

Ethchlorvynol injection in humans leads to a clinical picture consistent with increased permeability pulmonary edema, ie, the adult respiratory distress syndrome. There has been only one such case reported in which the pulmonary wedge pressure was measured. In an attempt to mimic the human disease, the authors established the awake, unanesthetized chronic sheep lung lymph fistula model and injected 15 mg/kg of ethchlorvynol intravenously after a baseline period. There were transient increases in pulmonary artery and systemic blood pressure with decreases in cardiac output. Lymph flow increased five-fold and remained elevated for 24 hr, returning to normal by 48 hr. All animals survived. Pulmonary morphologic changes consisted of alveolar and interstitial edema and some disruption of endothelial and epithelial cells. These findings resolved by 48 hr postinjection. The authors conclude that this model mimics the findings in humans who have injected ethchlorvynol intravenously.

Histamine Receptor and Prostaglandin Synthetase Blockers in Ethchlorvynol-Induced Pulmonary Edema in Canines

The injection of ethchlorvynol intravenously in humans and animals causes an increased permeability form of pulmonary edema. The proximate cause for this increased alveolar capillary membrane permeability is unknown but humoral mediators such as histamine and prostaglandins could play a role. To determine whether these agents were a factor in the altered permeability, we employed the saline-filled dog lung model and measured the flux of albumin across the alveolar capillary membrane. Following the intravenous injection of ethchlorvynol, there was a marked increase in permeability which was not altered by treatment with H1 and H2 receptor blockers or a prostaglandin synthetase inhibitor. We conclude that histamine and prostaglandins play no role in the increased permeability associated with ethchlorvynol injection.