In order to explore the effect of forest bathing on human immune function, we investigated natural killer (NK) activity; the number of NK cells, and perforin, granzymes and granulysin-expression in peripheral blood lymphocytes (PBL) during a visit to forest fields. Twelve healthy male subjects, age 37-55 years, were selected with informed consent from three large companies in Tokyo, Japan. The subjects experienced a three-day/two-night trip in three different forest fields. On the first day, subjects walked for two hours in the afternoon in a forest field; and on the second day, they walked for two hours in the morning and afternoon, respectively, in two different forest fields. Blood was sampled on the second and third days, and NK activity; proportions of NK, T cells, granulysin, perforin, and granzymes A/B-expressing cells in PBL were measured. Similar measurements were made before the trip on a normal working day as the control. Almost all of the subjects (11/12) showed higher NK activity after the trip (about 50 percent increased) compared with before. There are significant differences both before and after the trip and between days 1 and 2 in NK activity. The forest bathing trip also significantly increased the numbers of NK, perforin, granulysin, and granzymes A/B-expressing cells. Taken together, these findings indicate that a forest bathing trip can increase NK activity, and that this effect at least partially mediated by increasing the number of NK cells and by the induction of intracellular anti-cancer proteins.

We previously reported that the forest environment enhanced human natural killer (NK) cell activity, the number of NK cells, and intracellular anti-cancer proteins in lymphocytes, and that the increased NK activity lasted for more than 7 days after trips to forests both in male and female subjects. To explore the factors in the forest environment that activated human NK cells, in the present study we investigate the effect of essential oils from trees on human immune function in twelve healthy male subjects, age 37-60 years, who stayed at an urban hotel for 3 nights from 7.00p.m. to 8.00a.m. Aromatic volatile substances (phytoncides) were produced by vaporizing Chamaecyparis obtusa (hinoki cypress) stem oil with a humidifier in the hotel room during the night stay. Blood samples were taken on the last day and urine samples were analysed every day during the stay. NK activity, the percentages of NK and T cells, and granulysin, perforin, granzyme AlB-expressing lymphocytes in blood, and the concentrations of adrenaline and noradrenaline in urine were measured. Similar control measurements were made before the stay on a normal working day. The concentrations of phytoncides in the hotel room air were measured. Phytoncide exposure significantly increased NK activity and the percentages of NK, perforin, granulysin, and granzyme AlB-expressing cells, and significantly decreased the percentage of T cells, and the concentrations of adrenaline and noradrenaline in urine. Phytoncides, such as a-pinene and -pinene, were detected in the hotel room air. These findings indicate that phytoncide exposure and decreased stress hormone levels may partially contribute to increased NK activity.The forest environment has been enjoyed by humans for a long time because of the quiet atmosphere, beautiful scenery, mild climate, and clean fresh air. We previously reported that the forest environment enhanced human natural killer (NK) cell activity, the number of NK and NKT cells, and intracellular anti-cancer proteins in lymphocytes, and that the increased NK activity lasted for more than 7 days after the trips to forests both in male and female subjects (1-5). However, it is not clear what kind of factors in the forest environment activated human NK cells. We speculate that aromatic volatile substances derived from trees, including monoterpenes and sesquiterpenes, called phytoncides, such as a-pinene and limonene (6), may play an important role. Thus, the effects of phytoncides, such as a-pinene,

We evaluated cross-sensitization between p-phenylenediamine (pPDA) and p-aminophenol (pAP) or m-phenylenediamine (mPDA) by a modified lymphocyte transformation test. Guinea pigs were sensitized with pPDA using the maximization test procedure. Lymph node cells from the animals were then cultured with pPDA, pAP or mPDA in the presence or absence of epidermal cells (EC). Transformed lymphocyte counts were evaluated by means of 3H-thymidine uptake. Non-sensitized guinea pigs were used as controls. Blastogenesis in lymphocytes from sensitized guinea pigs was enhanced when cultured with pPDA, pAP or mPDA in the absence or presence of EC than without the sensitizers, and the extent of response depended on the concentration of pPDA, pAP or mPDA added to the cultures. Blastogenesis in lymphocytes from control animals was not significantly enhanced in response to pPDA, pAP or mPDA in the presence or absence of EC. The extent of the response to pPDA was greater than that to pAP, which in turn was greater than that to mPDA. In contrast, because pPDA, pAP and mPDA are color developing agents, cross-sensitization between pPDA and pAP or mPDA could not be evaluated by the results of an in vivo challenge due to pigmentation in the patch application sites. The results suggested that there is cross-sensitization between pPDA and pAP or mPDA, and that the modified lymphocyte transformation test is a useful predictive means of detecting cross-sensitization among chemicals, especially for color developing agents.

No abstract

No abstract