Key Points IL-2 induces expression of PD-1 on Tregs, and PD-1 blockade promotes Treg differentiation and apoptosis. PD-1 regulates IL-2–induced Treg proliferation and prolongs Treg survival in murine models and in patients receiving low-dose IL-2 therapy.

The aim of this study was to examine the effect of cytokines on different subsets of NK cells, while especially focusing on CD16− CD56dim cells and CD16− CD56bright cells. When human peripheral blood mononuclear cells (PBMC) were cultured with a combination of IL‐2, IL‐12 and IL‐15 for several days, a minor population of CD56bright NK cells expanded up to 15%, and also showed potent cytotoxicities against various cancer cells. Sorting experiments revealed that unconventional CD16− CD56+ NK cells (CD16− CD56dim NK cells and CD16− CD56bright NK cells, both of which are less than 1% in PBMC) much more vigorously proliferated after cytokine stimulation, whereas predominant CD16+ CD56dim NK cells proliferated poorly. In addition, many of the resting CD16− CD56bright NK cells developed into CD16+ CD56bright NK cells, and CD16− CD56dim NK cells developed into CD16− CD56bright NK cells and also further into CD16+ CD56bright NK cells by the cytokines. CSFE label experiments further substantiated the proliferation capacity of each subset and the developmental process of CD16+ CD56bright NK cells. Both CD16− CD56dim NK cells and CD16− CD56bright NK cells produced large amounts of IFN‐γ and Fas‐ligands. The CD16+ CD56bright NK cells showed strong cytotoxicities against not only MHC class I (−) but also MHC class I (+) tumours regardless of their expression of CD94/NKG2A presumably because they expressed NKG2D as well as natural cytotoxicity receptors. The proliferation of CD16+ CD56bright NK cells was also induced when PBMC were stimulated with penicillin‐treated Streptococcus pyogenes, thus suggesting their role in tumour immunity and bacterial infections.

The activity of pergolide, an N-propylergoline derivative, has been tested for stimulation of central dopaminergic receptors. Binding to dopamine receptors shows that pergolide acts as an agonist with respect to these receptors. GTP decreases the potencies of dopamine agonists and of pergolide, It is now established that the major abnormality in parkinsonism is the degeneration of the nigrostriatal 3,4-dihydroxyphenylethylamine (dopamine) neurons. The effectiveness of 3,4-dihydroxyphenylalanine (L-dopa) in parklnsonism is dependent on the capacity of the remaining nigrostriatal dopamine neurons to synthesize dopamine from administered L-dopa. It has become apparent that therapeutic response diminishes after prolonged treatment with L-dopa (1, 2). This decrease might be due to progressive degeneration of the nigrostriatal dopamine neurons or to a decreased sensitivity of dopamine receptors in the striatum. It was therefore of interest to investigate the effectiveness of drugs that directly stimulate dopamine receptors in the brain. Among various dopamine agonists tested, certain ergot alkaloids were found to stimulate dopamine receptors (3, 4), and their therapeutic effectiveness in parkinsonism was investigated (5, 6).We now describe dopamine agonist properties of a semisynthetic ergoline derivative, pergolide (8fl-[8-(methylthio)-methyl]-6-propylergoline), tested both in vitro and in two animal models that simulate certain features of parkinsonism. The potency of pergolide was compared with that of bromocriptine (2-bromo-a-ergocriptine), another ergot derivative currently used in the treatment of parkinsonism (7,8). The long duration of action of pergolide as an agonist (9, 10) prompted us to investigate its therapeutic effectiveness in parkinsonism patients. Preliminary reports on this study have been presented (9,11,12). MATERIALS AND METHODSNPA) (75 Ci/nmol) were purchased from New England Nuclear (1 Ci = 3.7 X 1010 becquerels). Pergolide was a gift from Eli Lilly, and bromocriptine from Sandoz Pharmaceutical.Binding Assay. Preparation of bovine or rat membranes and the ensuing binding assay were carried out as described (13). For routine assay each tube contained 1.8 ml. of membrane suspension (5 mg of wet tissue), 0. Values for the mean inhibitory concentration, ICso, were derived by log probit analysis. Values for the dissociation constant, Kd, for each radioactive ligand were determined from the corresponding Scatchard plots, and values for the inhibitor constant, Ki, were determined according to the equation Ki =

27 patients who underwent bilateral thalamotomy for parkinsonism over the past 10 years have been clinically evaluated. Mean follow-up period was 6.2 years after second surgery. In these cases, 8 returned to full social life without any medication, 4 were capable of social life with medical treatment, 6 were self-sufficient and 3 were semi-selfsufficient in ADL, respectively. Therapeutic drug doses were reduced in all cases. L-Dopa-induced dyskinesia was not observed after second surgery. Speech disturbance, which was not severe, was recognized in 12 cases as a complication.

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