The antiproliferative effects of interferon a (IFN-a) and interferon y (IFN-y) were found to be celldependent. Among the human cell lines examined, IFN-y had a greater antiproliferative effect against cell lines that exhibited induction of indoleamine 2,3-dioxygenase, such as the KB oral carcinoma or WiDr colon adenocarcinoma, than against those that lacked the enzyme activity, such as the SW480 colon adenocarcinoma or NCI-H128 small-cell lung carcinoma. MATERIALS AND METHODSCell Culture. Human cell lines HL-60 (promyelocytic leukemia), KG-1 (myelogenous leukemia), CCRF-SB (B-cell leukemia), CCRF-CEM (T-cell, leukemia), MOLT-4 (T-cell leukemia), THP-1 (monocytic leukemia), U-937 (histiocytic lymphoma), NCI-H69 and NCI-H128 (small-cell lung carcinomas), A-427 (lung carcinoma), MRC-5 (normal fetal lung), HEp-2 (larynx carcinoma), KB (oral carcinoma), MCF7 (breast adenocarcinoma), SW480 (colon adenocarcinoma), WiDr (colon adenocarcinoma), and I407 (normal embryonic intestine) were obtained from the American Type Culture Collection. The cells (0.3-1 x 106) were grown in 60-mm plastic culture plates (Costar, Cambridge, MA) containing 6 ml of culture medium consisting of 25 mM Hepes-buffered RPMI 1640 (GIBCO) with 10% heat-inactivated fetal bovine serum, penicillin (50 units/ml), and streptomycin (0.05 mg/ ml; Hazleton Research Products, Lenexa, KS) in the presence of IFN-a

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Indoleamine 2,3-dioxygenase (IDO) is an interferon (IFN)-induced protein that initiates the metabolism of tryptophan along the kynurenine pathway. Although IDO can be induced by IFN-gamma in many cell types, only mononuclear phagocytes have been shown to be induced to decyclize tryptophan by all three IFN classes. Since tryptophan is an essential amino acid necessary for a variety of metabolic processes, depletion of available tryptophan may be an important mechanism for control of rapidly-dividing microbial pathogens and tumors. The purpose of this review is to present evidence that documents the effects of IFN-induced IDO on prokaryotic and eukaryotic pathogens, as well as on a variety of tumor cell lines.

Melatonin was shown to occur in rat plasma and urine after pinealectomy by bioassay, radioimmunoassay, and thin-layer chromatography. Total daily excretion of melatonin in pinealectomized rats was about 20% of control. Light-dark rhythms of plasma melatonin levels and urinary excretion rates disappeared after pinealectomy.

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