Analysis of mechanisms of cell death of T-lymphocytes induced by organotin agents.

Organotin compounds are known to cause thymic atrophy and an accompanying deficiency of cell-mediated immunity. The study reported here focused on cell death in the thymus as a contributing factor in the induction of thymic atrophy following exposure to dibutyltin (DBTC) and tributyltin (TBTC). In an in vivo study, a reversible thymic atrophy was induced in rats by a single intraperitoneal administration (2.0 mg/kg) of DBTC or TBTC; the magnitude of this effect over a 4-d post-treatment period differed between the two agents. In in vitro studies, T-lymphocytes were isolated from thymuses of naïve rats and then exposed to 1 microM DBTC or TBTC for varying periods of time. Analysis by flow cytometry showed that DBTC induced primarily necrosis, while TBTC induced apoptosis, of the cells. Activities of caspase-8, -9, and -3 were also measured; TBTC exposure caused marked increases in the activities, while DBTC exposure did not cause any significant change. TBTC exposure also appeared to induce expression of CAD (which fragments DNA), but had minimal effect on levels of the CAD inhibitor, ICAD. In contrast, DBTC exposure resulted in a larger level of ICAD expression. WST-8 and JC-1 assays were used to evaluate mitochondrial function, since a strong activation of caspase-9 by TBTC suggested mitochondrial involvement. The involvement of caspase in the activation was examined using cytochrome c expression; cytochrome expression and the loss of mitochondrial function occurred within 10 min of TBTC exposure. DBTC exposure affected the mitochondria less. These results indicated that effects on mitochondria likely played an important role in the induction of apoptosis by TBTC. The results of this study show that DBTC and TBTC induce necrosis and apoptosis of T-lymphocytes, respectively, by apparently indicating different mechanisms of cell death. It follows that these increases in cell death induced by these organotin compounds likely contributed to the thymic atrophy observed in the rats here.

Research report: Frequencies of mica gene polymorphism: a comparison between Indonesians on Bacan Island and suburban Japanese.

MHC class I chain related gene A (MICA) is located near the HLA-B gene on the short arm of human chromosome 6. In the transmembrane (TM) of region of MICA, there is a trinucleotide repeat (GCT/AGC) microsatellite polymorphism in exon 5. Five alleles with 4, 5, 6 and 9 repetitions or 5 repetitions with 1 additional nucleotide insertion (GGCT) are identified and they were named A4, A5, A5.1, A6, and A9 respectively. We report the allele frequencies of 127 Indonesians on Bacan Island and 250 Japanese in the Kanto area. From the genotyping result, the frequency among Indonesians was as follows: A4 15.4%, A5 26.0%, A5.1 16.5%, A6 5.5%, and A9 36.6%. The frequency among Japanese was as follows: A4 20.6%, A5 28.1%, A5.1 10.8%, A6 27.2%, and A9 13.2%. Allele 9 is significantly increased and allele 6 significantly decreased in Indonesians compared with Japanese subjects. The results suggested that MICA microsatellite polymorphism are quite different in each race. Among Indonesians, the frequency of MICA-A9 allele, which was reported to be negatively associated with Behçet's disease, was significantly higher, whereas the MICA-A6 allele frequency, which was reported to be positively associated with Behçet's disease, was significantly lower among Japanese.

Exhaustive exercise and type-1/type-2 cytokine balance with special focus on interleukin-12 p40/p70.

It is known that interleukin (IL)-12 p70 promotes the differentiation of type-1 helper T (Th1) cells, which produce type-1 cytokines such as IL-2 and interferon (IFN), thereby supporting cellular immunity, whereas IL-12 p40 acts as an antagonist of IL-12 p70. In contrast, IL-4 and IL-6 promote the differentiation of Th2 cells, which produce type-2 cytokines IL-4, IL-6 and IL-10, induce humoral immunity and are involved in allergic reactions. Exhaustive exercise causes the suppression of T lymphocyte activity while asthmatic and allergic diseases are subclinically more prevalent in athletes. One of the mechanisms behind these observations might be a lower type-1 and higher type-2 cytokine balance, which we previously demonstrated to occur after exhaustive exercise. In the present study, we investigated the type-1/type-2 cytokine balance by measuring plasma concentrations of IL-2, IL-4, IL-5, IL-10, tumor necrosis factor (TNF)-alpha and IFN-gamma with microparticle-based flow cytometric technology. IL-5, IL-6 and IL-13 were measured by enzyme-linked immunosorbent assay (ELISA). IL-12 p40 and p70 were measured separately, also by ELISA. Plasma IL-12 p40 concentration rose significantly after maximal exercise and to an even greater extent after a marathon race. Conversely, plasma IL-12 p70 could not be detected even using two different assays. The marathon race caused a marked increase in the plasma concentrations of IL-6 and IL-10. Their responses were correlated (r = 0.78, p < 0.01), indicating that IL-6 is an inducer of IL-10, and may partly induce the type-1 < type-2 cytokine balance. With the exception of one study involving maximal exercise, other studies have failed to show any change in circulating IL-12 concentration with exercise. The present study demonstrated that IL-12 p40 was present in excess of p70 especially after exercise. This may be one of the mechanisms behind several phenomena including cellular immunosuppression, an increase in the relative proportion of type-2 cytokines following exhaustive exercise, and the higher incidence of infections and allergic disorders in regularly exercising endurance athletes.

Differential effects of physical and psychological stressors on immune functions of rats.

To study the effects of different types or durations of stressors on immune functions, male Fischer rats were exposed to chronic physical (electric foot shock) or psychological (non-foot shock) stress induced in the communication box. Superoxide production by alveolar macrophages (AMs), mitogen-induced splenic lymphocyte proliferation, and splenic natural killer (NK) cell cytolysis were examined in vitro. Repeated exposure to physical stress suppressed superoxide production by AMs (-58%, p<0.05 for opsonized zymosan (OZ) and -51%, p<0.05 for phorbol 12-myristate 13-acetate (PMA)), although psychological stress suppressed superoxide production after 24 h of repeated exposures (-40%, p<0.05 for OZ and -47%, p<0.05 for PMA). Acute suppression of the blastic response of splenic lymphocytes was only found in the physical stress group (p<0.05), although the chronic effects were only found in the psychological stress group (p<0.05). NK cell activity was suppressed immediately after the acute physical stress (-30%, p<0.05), but no effects were found in the psychological stress group. These results underline the importance of distinguishing between physical versus psychological stressors when examining the effects of stress on immune functions.

A study among related pairs of Japanese patients with familial Behçet's disease: group comparisons by interval of disease onsets.

OBJECTIVE: To investigate the relationship between clinical features and the interval between onset of disease in pairs of related Japanese patients with Behçet's disease (BD). METHODS: Questionnaires were sent to hospitals in which patients with familial occurrence of BD had been treated according to previous nationwide hospital surveys, and to an additional 341 hospitals selected at random. RESULTS: A total of 35 patients (19 male, 16 female) in 17 families (19 related pairs) were reported. The positive rate of HLA-B51 was 60.9% (14/23). The familial pairs were divided into 2 groups, with the mean interval between disease onset between each pair being either < or = 9 years or > or = 10 years. Among the short interval group, the total number of clinical findings and difference in age of onset was significantly larger than the long interval group. The interval between onsets had a high positive correlation with concordance of clinical findings and a high negative correlation with the difference in onset age. Difference in onset age had a higher negative correlation with same sex. Moreover, age difference had a high negative correlation with HLA-B5 (B51). Analysis of data showed that the related pairs with the short interval between onsets had larger difference in onset age and greater concordance of symptoms than the long interval patients. CONCLUSION: Although our findings did not show any direct evidence of an environmental cause in the etiology of BD, we speculate that there may be a multifactorial etiology including genetic factors such as HLA-B51 positivity.