Neuroimmunomodulation with enkephalins: in vitro enhancement of natural killer cell activity in peripheral blood lymphocytes from cancer patients.

To initiate investigations into the effects of enkephalins on immune function in cancer patients, the effect of methionine-enkephalin and leucine-enkephalin on natural killer (NK) cell activity in isolated peripheral blood lymphocytes from cancer patients was investigated. Incubation of lymphocytes with either enkephalin resulted in significant increases in NK cell activity. At effector:target cell ratios of 100:1, 33:1 and 11:1 leucine-enkephalin significantly (p less than 0.05) enhanced NK activity at dilutions of 10(-6), 10(-8), 10(-10), and 10(-14) mg/ml. Similar results were obtained with methionine-enkephalin with the exception that the 10(-6) dilution gave insignificant changes at both the 33:1 and 11:1 cell ratios. The results indicate a difference in dose response to both enkephalins between lymphocytes from cancer patients and normal volunteers.

Role of hydrogen peroxide in neutrophil-mediated destruction of cultured endothelial cells.

Human neutrophils stimulated with phorbol myristate acetate were able to destroy suspensions or monolayers of cultured human endothelial cells. Neutrophil-mediated cytotoxicity was related to phorbol myristate acetate concentration, time of incubation and neutrophil number. Cytolysis was prevented by the addition of catalase, while superoxide dismutase had no effect on cytotoxicity. The addition of the heme-enzyme inhibitors, azide or cyanide, markedly stimulated neutrophil-mediated damage while exogenous myeloperoxidase failed to stimulate cytolysis. Neutrophils isolated from patients with chronic granulomatous disease did not destroy the endothelial cell targets while myeloperoxidase-deficient neutrophils successfully mediated cytotoxicity. Endothelial cell damage mediated by the myeloperoxidase deficient cells was also inhibited by catalase but not superoxide dismutase. The addition of purified myeloperoxidase to the deficient cells did not stimulate cytotoxicity. Glucose-glucose oxidase, an enzyme system capable of generating hydrogen peroxide, could replace the neutrophil as the cytotoxic mediator. The addition of myeloperoxidase at low concentrations of glucose oxidase did not increase cytolysis, but at the higher concentrations of glucose oxidase it stimulated cytotoxicity. The destruction of endothelial cells by the glucose oxidase-myeloperoxidase system was inhibited by the addition of hypochlorous acid scavengers. In contrast, neutrophil-mediated cytolysis was not effectively inhibited by the hypochlorous acid scavengers. Based on these observations, we propose that human neutrophils can destroy cultured human endothelial cells by generating cytotoxic quantities of hydrogen peroxide.

Disorders of iron metabolism.

Although iron in minute amounts is necessary for the metabolism of most cells, it produces damage if present in excess. Clinical tools for the evaluation of iron stores include serum iron concentration, transferrin saturation, deferoxamine test, Prussian blue stains of liver and marrow, and serum ferritin concentration. Serum ferritin concentration is an excellent screening test for iron deficiency or excessive iron stores. If excessive iron stores is diagnosed, the iron should be removed with phlebotomies or chelation therapy.