Analysis of blood lymphocyte subsets in children living around Chernobyl exposed long-term to low doses of cesium-137 and various doses of iodine-131

Epidemiological studies have found that children living around Chernobyl have rates of respiratory tract illness that are higher than those seen in the area before the Chernobyl accident. The present study investigates the possible effects of radiation exposure on the composition of peripheral blood lymphocyte subsets in children living around Chernobyl. Two hundred nineteen healthy children and children suffering from recurrent respiratory diseases aged 6-14 years who received both low doses of radiation to the whole body from (137)Cs and various doses of radiation to the thyroid from (131)I as fallout from the accident were assessed 5 (1991) and 8-10 years (1994-1996) after the accident. A total of 148 healthy children and children suffering from recurrent respiratory diseases living in noncontaminated areas were also evaluated as controls. Children with recurrent respiratory diseases who lived around Chernobyl had a significantly lower percentage of T cells and a higher percentage of NK cells compared to control children with recurrent respiratory diseases during the study period. In contrast to the findings in 1991, a significant decrease in the percentage of helper-inducer cells was observed in children with recurrent respiratory diseases in 1994-1996. In contrast to 1991, there is a positive correlation between the percentage of helper-inducer cells, the helper-inducer/cytotoxic-suppressor cell ratio, and the dose of radiation to the thyroid of healthy children from (131)I in 1994-1996. There was a positive correlation between the dose of radiation to the thyroid from (131)I and the percentage of helper-inducer cells in children with recurrent respiratory diseases 5 years (1991) after the accident. Further, the dose of radiation to the thyroid from (131)I correlated negatively with the percentage of T and B cells and positively with the percentage of NK cells in children with recurrent respiratory diseases 8-10 years (1994-1996) after the accident. These results raise the possibility that long-term exposure to low doses of (137)Cs may have altered the composition of the T-cell subsets and NK cells in children with recurrent respiratory diseases. The differences in the composition of the peripheral blood lymphocyte subsets between healthy children and those with recurrent respiratory diseases may be attributed to long-term low-dose exposure of the whole body to radiation from (137)Cs and exposure of the thyroid to radiation from (131)I subsequent to the Chernobyl accident.     

The problem of the transgeneration phenomenon of genome instability in sick children of different age groups after the accident at the Chernobyl Nuclear Power Plant

A complex genetic examination of children which belong to two cohorts and their parents were carried out. The first cohort included children and constantly living on territories contaminated with radionuclides (Novozybkov district, Bryansk region). They were subdivided in groups according to the ontogenetic age periods of development of their parents at the time of the Chernobyl accident. In the children born in 1986-1995 the level of aberrant genomes is significantly higher as compared to the control (p < 0.001). In children born in 1998-2002 the differences are insignificant (p > 0.05). The frequency of aberrant genomes had a tendency to decrease with the period of time between the birth date of a child and the moment of the accident. Analysis of the results of cytogenetic investigation for the same living on territories with different densities of radioactive contamination (zone I-- 627-688 kBq/m2, 137Cs and zone II-- 135-402 kBq/m2, 137Cs) revealed insignificant differences in the spectrum and average frequencies of chromosome aberrations. The second cohort included children born in 1987-1991 and 1993-2002 from irradiated fathers (Chernobyl clean-up workers) and unirradiated mothers living on territories without radionuclide contamination. These children also displayed increased frequencies of aberrant genomes as compared to the control (p < 0.001). The analysis of the dynamics years of birth of cytogenetic disturbances in the same cohorts of children showed the average frequencies of aberrant genomes remain higher than the control level. In most of the children of both cohorts the repair synthesis of genome DNA by gamma- and UV-radiation is reduced as compared to one in the children from the control group.     

The epidemiological analysis of monitoring of the immune status in liquidators of consequences of the Chernobyl accident for early identification of risk groups and diagnostics of oncological diseases. Report 1

Ionizing radiation is one of major factors of risk of oncological diseases. A question about the frequency of malignant neoplasms (MN) and their early identification in the liquidators of consequences of the Chernobyl accident remains opened. In the present work, the results of long-term immunological monitoring of the liquidators of consequences of the failure at the Chernobyl Nuclear Power Plant (ChN PP) living in the Northwest region of Russia are analyzed; we also heve made an attempt to reveal the predictors of oncological diseases in this group of individuals. The frequency of the newly revealed MN cases in a cohort of the persons who took part in liquidation of consequences of the ChNPP failure and were followed-up in 1999-2009, has made up 89 cases per 1005 persons (8.856%), which somewhat exceeds general population indicators. Regarding the frequency of separate MN localizations, lung cancer, cancer of stomach and cancer of prostate gland predominated, which corresponds to the world's tendency of MN prevalence. It has been established that as early as 1-3 years before diagnosis of MN is confirmed in liquidators, a number of changes in the immune status comes to light: drop in percentage of CD3+ and CD4(+)-T-lymphocytes, B-lymphocytes to a lesser extent, decrease in the CD4+/CD8+ index, increase of the relative and absolute content of CD16(+)-lymphocytes, increase of absolute content of CD8(+)-T-lymphocytes, prevalence of CD3+16/56+(NK-T) cell over CD3-16/56+(NK) cells, rise of the activity of phagocytes. Patients with the presence of one or several of the above-mentioned signs should be attributed to the MN risk group for determination of tumor markers, thorough examination and dynamic observation.     

The connection between molecular-cellular parameters and immune status of liquidators after Chernobyl accident

The genome damage (the frequencies of cells with micronuclei (MN), chromosome aberrations, the level of DNA double-strand breaks (DSB DNA), the concentration of reactive oxygen species (ROS) and 28 immunological parameters have been studied on the blood lymphocytes of Chernobyl accident liquidators. The purpose of this article was the investigation of cytogenetic, molecular changes of blood lymphocytes of irradiated individuals 24 years after accident, examination it there are correlation between genome damage and immunological parameters. It was shown that in lymphocytes of liquidators the frequencies of cells with MN and with all type of chromosome aberrations didn't differ from the lymphocytes of nonirradiated individuals, but the frequency of chromosome aberration type was increased, the level of DSB DNA was increased too. The concentration of ROS is decreased. The percent of cytotoxic CD8(+)-T-lymphocytes, natural killer cells (CD16(+)-lymphocytes), CD3+ CD16+ CD56+ (NK-T-cells), that posses antivirus and antitumor activity--HLA-DR+, regulatory T-lymphocytes (CD4+ CD25+high) in liquidators significantly increases. The level of serum immunoglobulin (Ig A) significantly increases too. The index of immune regulation, meaning of phagocyte neutrophil (FAN) and macrophage activity decreases. In liquidators there are significant correlation between the frequencies of cells with MN and the content of regulatory T-lymphocytes (p < 0.05), between the concentrations of ROS and activated T-lymphocytes. More connection is on the tendency level (p < 0.10): the frequency of chromosome aberrations, the DSB DNA level with natural killer cells and regulatory T-lymphocytes; the frequency of cells with MN and DSB DNA and FAM. We can suppose that genomic instability induced by the liquidators of Chernobyl accident consequences 24 years ago manifests now as increased genome damage and oxidative status decrease that can result in imbalance of cells and humoral immune status, disturbancies of health.     

Micronucleus frequency in Gomel (Belarus) children affected and not affected by thyroid cancer.

Cytogenetic monitoring was carried out on a group of children from Gomel (Belarus), one of the areas most severely affected by radioactive contamination following the accident at the Chernobyl nuclear power plant, in 1986. We performed the micronucleus test (MN) in binucleated lymphocytes of 42 children (mean age: 11+/-2.34 years), 16 of whom were affected by thyroid gland tumor. Thirty healthy children living in Pisa (mean age: 14.96+/-2.17 years) were enrolled in the study as controls. Thyroid tumor affected children living in Gomel showed a statistically significant increase in the frequency of micronucleated cells as compared with the healthy children from Pisa. Moreover, a significant correlation was found between MN frequency and both the presence of tumor and higher 137Cs contamination. In addition, higher 137Cs contamination was more frequently observed in tumor affected children. These results suggest that the increased MN frequency is attributable more to 137Cs contamination rather than to the presence of the tumor itself.     

Marked expansion of CD11c+CD8+ T-cells in melanoma-bearing mice induced by anti-4-1BB monoclonal antibody

4-1BB (CD137), a member of the tumor necrosis factor receptor superfamily, is expressed on activated T-cells, and 4-1BB signaling due to interaction with 4-1BB ligand or ligation with anti-4-1BB monoclonal antibody (mAb) costimulates T cells. It has been shown that administration of anti-4-1BB mAb induces anti-tumor immunity in mice, but the nature of the cellular subsets responsible for this immunity is uncertain. In this study we found that anti-4-1BB mAb administration to B16F10 melanoma-bearing mice induced marked expansion of CD11c+CD8+ T-cells in parallel with suppression of pulmonary tumors. The mAb-treated mice produced higher levels of IFN- in their tumor tissues, spleen and lymph nodes than mice exposed to control antibody. When the CD11c+CD8+ T-cells were purified and re-stimulated in vitro, they produced high levels of the Th1 cytokines, IFN- and IL-2, but low levels of the Th2 cytokines, IL-4 and IL-10. Furthermore, they expressed high levels of 4-1BB and CD107a, a marker of activated cytotoxic T-lymphocytes. Our results suggest that CD11c+CD8+ T-cells play a role in the anti-tumor immunity induced by anti-4-1BB mAb.     

Cancer incidence in northern Sweden before and after the Chernobyl nuclear power plant accident

Sweden received about 5 % of the total release of ¹³⁷Cs from the Chernobyl nuclear power plant accident in 1986. The distribution of the fallout mainly affected northern Sweden, where some parts of the population could have received an estimated annual effective dose of 1–2 mSv per year. It is disputed whether an increased incidence of cancer can be detected in epidemiological studies after the Chernobyl nuclear power plant accident outside the former Union of Soviet Socialist Republics. In the present paper, a possible exposure–response pattern between deposition of ¹³⁷Cs and cancer incidence after the Chernobyl nuclear power plant accident was investigated in the nine northernmost counties of Sweden (2.2 million inhabitants in 1986). The activity of ¹³⁷Cs from the fallout maps at 1986 was used as a proxy for the received dose of ionizing radiation. Diagnoses of cancer (ICD-7 code 140-209) from 1980 to 2009 were received from the Swedish Cancer Registry (273,222 cases). Age-adjusted incidence rate ratios, stratified by gender, were calculated with Poisson regression in two closed cohorts of the population in the nine counties 1980 and 1986, respectively. The follow-up periods were 1980–1985 and 1986–2009, respectively. The average surface-weighted deposition of ¹³⁷Cs at three geographical levels; county (n = 9), municipality (n = 95) and parish level (n = 612) was applied for the two cohorts to study the pre- and the post-Chernobyl periods separately. To analyze time trends, the age-standardized total cancer incidence was calculated for the general Swedish population and the population in the nine counties. Joinpoint regression was used to compare the average annual percent change in the general population and the study population within each gender. No obvious exposure–response pattern was seen in the age-adjusted total cancer incidence rate ratios. A spurious association between fallout and cancer incidence was present, where areas with the lowest incidence of cancer before the accident coincidentally had the lowest fallout of ¹³⁷Cs. Increasing the geographical resolution of exposure from nine county averages to 612 parish averages resulted in a two to three times higher value of variance in the regression model. There was a secular trend with an increase in age-standardized incidence of cancer in both genders from 1980 to 2009, but significant only in females. This trend was stronger and statistically significant for both genders in the general Swedish population compared to the nine counties. In conclusion, using both high quality cancer registry data and high resolution exposure maps of ¹³⁷Cs deposition, it was not possible to distinguish an effect of ¹³⁷Cs on cancer incidence after the Chernobyl nuclear power plant accident in Sweden.     

The change in efficiency of protective measures for reduction of 137Cs accumulation by agricultural plants in various periods after the Chernobyl accident

Dynamics of 137Cs transfer factors to plants and the effects of protective measures on this radionuclide accumulation in the agricultural production is estimated on the example of the south-western regions of Bryansk District. Three periods in decreasing the 137Cs content in plants during 20 years after the Chernobyl accident are identified. The contribution of radionuclide decay, natural biogeochemical processes and protective measures aimed at reduction of the 137Cs accumulation in agricultural plants during various periods after radioactive fallout is shown. Maximum permissible levels of 137Cs contamination of cultivated lands, where crop products meeting current standards may be obtained, at different scopes of protective measures on radioactive-contaminated territories are forecasted. Periods after radioactive fallout, when crop and forage products meeting radiological standards are obtained, are assessed.     

The radiological situation before and after Chernobyl disaster

The nuclear reactor accident, which occurred on 26 April 1986 at Chernobyl, has been one of the greatest ecological disasters in human history. In our study we discussed the most recent data on the accident, and the natural and synthetic sources of radiation. According to the recent data, the air at Chernobyl had been contaminated with about 5300 PBq radionuclide activity (excluding rare gases), including 1760 PBq (131)I and 85 PBq (137)Cs. The highest radiation received by the liquidators (0.8-16 Gy), lower doses were received by the population which was evacuated or inhabited the contaminated areas (in which the level of (137)Cs activity deposited in the earth was 37 kBq/m(2)). In the European countries the highest mean radiation dose per year for the whole body in the first year after the accident was in Bulgaria (760 microSv), Austria (670 microSv) and Greece (590 microSv), while the lowest radiation dose was observed in Portugal (1.8 microSv) and Spain (4.2 microSv). In Poland the mean effective equivalent dose resulting from Chernobyl accident was 932 microSv and is close to the limited dose permitted in Poland, equalling 1 mSv/year. The highest radiation dose to thyroid was received by inhabitants of the states previously known as Bielskopodlaskie, Nowosadeckie and the north-east region of Poland. Lowest dose was received by inhabitants of the areas previously known as Slupski and Rzeszowski.     

Natural killer cells activate human dermal fibroblasts

Human dermal fibroblasts (HDF) undergo activation and secrete cytokines when cocultured with T cells. Here, we identify potent activators of HDF among human peripheral CD2(+)-lymphocytes. Populations with strong HDF activating capacity consisted essentially of cells with a natural killer (NK) surface marker phenotype (CD3(-), CD4(-), CD8(-), CD56(+)). Addition of these cells to HDF resulted in rapid increase of intracellular free calcium concentrations as an early rapid cell activation signal. Upregulation of mRNA encoding for the inflammatory cytokines IL-1 beta and IL-6 as well as for chemokines IL-8 and MCP-1 was detected after cells were cocultured. Elevated concentrations of IL-6 and IL-8 were found in coculture supernatants of HDF and NK-cells. Skin-homing NK cells leaving the blood-stream during an inflammatory skin reaction might therefore represent potent activators of local inflammatory cytokine and chemokine production.     

An assessment of the permissible level of a mixture of radionuclides from the Chernobyl fallout in human lungs]

The permissible level of a radionuclide mixture, resulted from the Chernobyl burst, in the human being lungs was determined for two kinds of compounds: absolutely insoluble compounds and soluble compounds in the state of equilibrium. For this purpose the data were used concerning the radionuclide composition and aerosol disperse in lower atmosphere which were obtained by the Department for Dosimetric Control (NPO "Pripiat'"). The results of measurements of 137Cs content taken by the use of human radiation spectrometer (HRS) needed an adequate estimation: low level of 137Cs in the human lungs and body within the Chernobyl NPP, zone does not guarantee radiation security. The notion "permissible content" and the possibility of using thereof in the individual dosimetric control are discussed.     

Late effects of the Chernobyl radiation accident on T cell-mediated immunity in cleanup workers

The main goal of this investigation was to evaluate the abnormal T-cell immunity in cleanup workers who took part in the cleanup after the Chernobyl accident in 1986. Peripheral blood mononuclear cells (MNCs) of apparently healthy cleanup workers (n = 134) were used to analyze the phenotype and proliferative response to mitogens in vitro. Evaluation of the MNC phenotype of cleanup workers did not reveal a significant disturbance in the T-cell subpopulation content except for an increase in CD3+CD16+56+ (NKT) cells. Immunophenotyping of phytohemagglutinin (PHA)-activated MNCs demonstrated suppression of CD4+ T-cell propagation and augmentation of CD8+ T-cell propagation in vitro compared to control individuals. DNA synthesis in the MNCs of cleanup workers was markedly inhibited after activation for 3 days with suboptimal concentrations of PHA, pokeweed mitogen and PMA. In contrast to control individuals, the monocytes of cleanup workers were able to stimulate the proliferation of T cells from healthy individuals but inhibited the proliferation of T cells from cleanup workers. This study affords a better understanding of the response of MNCs to stimulation with suboptimal concentrations of PHA and provides an approach to a more accurate analysis of the immunological disorders found after exposure to radiation from Chernobyl-related activities.     

Genomic instability in chidren born after the Chernobyl Nuclear Accident (in vivo and in vitro studies)

Analysis of peripheral blood lymphocytes in children born after the accident at the Chernobyl Nuclear Power Plant in the period from 1987 to 2004 (permanent residents of territories contaminated with radionuclides, n = 92; and children of irradiated fathers-liquidators, n = 88) revealed increased levels of aberrant cells (ACs) and aberrations of the chromosomal type as compared to the control (P < 0.05). In three subgroups of children with different initial AC frequencies (children with high AC frequencies, ≥3%; children with medium AC frequencies, 2%; and children with low AC frequencies, ≤1%), the levels of aberrations of the chromosomal type are increased as compared to the control (P < 0.05). The levels of aberrant cells and chromosome aberrations (CAs) in the subgroup of children with ≥3% frequencies significantly differ from those in the subgroup of children with ≤1% AC frequencies. No dependence of the AC and CA frequencies on the year of birth after the Chernobyl accident was revealed. After fractional and single γ-irradiation (137Cs) of blood in vitro in the 10–30 cGy dose range, the average CA frequencies in the first and second mitoses increased in a similar way depending on the initial AC frequencies in the children and parents. All these results suggest an individual character of genomic instability induced by low radiation doses and its transgenerational phenomenon in the organisms of children.     

The role of tumor cells in the modification of T lymphocytes activity--the expression of the early CD69+, CD71+ and the late CD25+, CD26+, HLA/DR+ activation markers on T CD4+ and CD8+ cells in squamous cell laryngeal carcinoma. Part I

The role of interactions between tumor cells and autologous immunocompetent cells, the impact on the modulation of the activity of T CD4(+) and CD8(+) lymphocytes, as well as the influence on the regulation and determination of antitumor cellular immune response in patients with head and neck squamous cell carcinomas (HNSCC) is not completely clear. The aim of this study was to analyze early and late activation antigens expression on T cells subpopulations modified under the influence of the presence of cancer cells to investigate the regulatory mechanisms of the local cellular immune response in carcinoma of the larynx. Cytofluorymetric analysis of the early (CD69(+), CD71(+)) and late activation markers (CD25(+) (high), CD26(+), HLA/DR(+)) expression on T CD3(+)CD4(+) and CD3(+)CD8(+) cells subpopulations in mixed cellular cultures of freshly isolated tumor cells (MLTMC) and non-cancerous normal epithelial cells (MLNCC) with immunocompetent cells was performed in 55 cases of squamous cell laryngeal carcinoma. The whole peripheral blood concentrations of IL-10 and IFN-γ in 21 h and 72 h of experiments were also measured by ELISA. The relationships between the activation markers expression depending on the type of cells used in co-cultures, as well as the level of secreted cytokines, were investigated. Our work has revealed a statistically significant dependence of cytofluorymetric results on the presence of TMC or NCC in mixed cellular cultures. Increased expression of CD69(+), CD71(+) and CD25(+) (high), CD26(+), HLA/DR(+) antigens on T CD3(+)CD4(+) and CD3(+)CD8(+) cells was higher in MLTMC cultures, in comparison with MLNCC. We demonstrated negative significant relationships of IFN-γ and IL-10 secretion with regard to CD4(+)CD69(+), CD8(+)CD69(+), CD4(+)CD71(+), CD8(+)CD71(+) antigens expression in 21 h of experiments without mitogenic stimulation. Furthermore, this study revealed negative significant relationships of IFN-g secretion with regard to CD4(+)HLA/DR(+) and CD8(+)HLA/DR(+) as well as between IL-10 concentration and CD4(+)HLA/DR(+) in trials without PHA stimulation. Our findings have confirmed a key role for tumor cells in determining the function of T cells involved in the immunological processes and impact of neoplastic cells on modulating the activity of T CD4(+) and CD8(+) lymphocytes in laryngeal carcinoma.     

Monte-Carlo prediction of changes in areas of west Cumbria requiring restrictions on sheep following the Chernobyl accident

Following the 1986 Chernobyl accident radiocaesium levels in sheep meat in some upland areas of the United Kingdom were above the national intervention limit. West Cumbria was one of these areas and restrictions are currently still in place. In addition to deposition from the Chernobyl accident, Cumbria has been subject to radiocaesium deposition from atmospheric nuclear weapons tests, the 1957 Windscale accident and routine releases from the Sellafield nuclear reprocessing plant. A Monte-Carlo approach has been used to try to predict areas in west Cumbria where radiocaesium activity concentrations in lamb meat would require the imposition of restrictions at different times after the Chernobyl accident. The approach models the transfer of radiocaesium from soil to vegetation, based upon soil organic matter, and from vegetation to lamb meat. Spatial inputs are soil organic matter and total post-Chernobyl (137)Cs and (134)Cs deposition; a ratio of Chernobyl (137)Cs to (134)Cs deposition has been used to differentiate Chernobyl and pre-Chernobyl (137)Cs deposition. Comparisons of predicted radiocaesium transfer from soil-vegetation and the spatial variation in lamb (137)Cs activity concentrations are good and predicted restricted areas with time after Chernobyl compare well to the restricted areas set by UK government. We predict that restrictions may be required until 2024 and that in some areas the contribution of pre-Chernobyl (137)Cs to predicted lamb radiocaesium activity concentrations is significant, such that restrictions may only have been required until 1994 as a consequence of Chernobyl radiocaesium deposition alone. This work represents a novel implementation of a spatial radioecological model using a Monte-Carlo approach.     

Possible Relationships between Plasma Glutathione Levels and Cytogenetic Indices in Peripheral Blood Lymphocytes of Children Exposed to Low Doses of Radiation

An analysis of correlations between cytogenetic indices in lymphocytes and levels of reduced glutathione in the plasma of peripheral blood in children born after the Chernobyl accident is presented. The studied systems in the child population demonstrated different responses to low-level radiation of their mothers living in conditions of radionuclide contamination (1–20 Ci/km² of ¹³⁷Cs). Low doses of radiation accumulated by mothers (below 30 cSv) proved to have a more pronounced effect on the studied systems in children as compared to high doses (from 30 to 60 cSv).     

MDR1 gene transfer using a lentiviral SIN vector confers radioprotection to human CD34+ hematopoietic progenitor cells

Tumor radiotherapy with large-field irradiation results in an increase in apoptosis of the radiosensitive hematopoietic stem cells (CD34(+)). The aim of this study was to demonstrate the radioprotective potential of MDR1 overexpression in human CD34(+) cells using a lentiviral self-inactivating vector. Transduced human undifferentiated CD34(+) cells were irradiated with 0-8 Gy and held in liquid culture under myeloid-specific maturation conditions. After 12 days, MDR1 expression was determined by the rhodamine efflux assay. The proportion of MDR1-positive cells in cells from four human donors increased with increasing radiation dose (up to a 14-fold increase at 8 Gy). Determination of expression of myeloid-specific surface marker proteins revealed that myeloid differentiation was not affected by transduction and MDR1 overexpression. Irradiation after myeloid differentiation also led to an increase of MDR1-positive cells with escalating radiation doses (e.g. 12.5-16% from 0-8 Gy). Most importantly, fractionated irradiation (3 x 2 Gy; 24-h intervals) of MDR1-transduced CD34(+) cells resulted in an increase in MDR1-positive cells (e.g. 3-8% from 0-3 x 2 Gy). Our results clearly support a radioprotective effect of lentiviral MDR1 overexpression in human CD34(+) cells. Thus enhancing repopulation by surviving stem cells may increase the radiation tolerance of the hematopoietic system, which will contribute to widening the therapeutic index in radiotherapy.     

DNA damage evaluated by the comet assay in lymphocytes of children with 137Cs internal contamination caused by the Chernobyl accident

The comet assay is one of the most versatile and popular tools for evaluating DNA damage. Its sensitivity to low dose radiation has been tested in vitro, but there are limited data showing its application and sensitivity in chronic exposure situations. The influence of the internal contamination caused by the Chernobyl accident on the level of DNA damage was evaluated by the comet assay on lymphocytes of 56 Ukrainian children. The study was performed during 2003 on children with demonstrable 137Cs internal contamination caused by food consumption. The children were selected for the study immediately after a 137Cs whole body counter measurement of internal contamination. The minimal detectable amount of 137Cs was 75 Bq. The control group included 29 children without detectable internal contamination, while in the exposed group 27 children with measured activity between 80 and 4037 Bq and committed effective dose between 54 and 3155 microSv were included. Blood samples were taken by a finger prick. The alkaline version of the comet assay was used, in combination with silver stained comets and arbitrary units (AU), for comet measurement. Factors such as disease, medical treatment, surface contamination of children's living location, etc., were considered in the study. Non-significant differences (p > 0.05) in DNA damage in control (9.0 +/- 5.7 AU) versus exposed (8.5 +/- 4.8 AU) groups were found. These results suggest that low doses of 137Cs internal contamination are not able to produce detectable DNA damage under the conditions used for the comet assay in this study. Further studies considering effects of high exposure should be performed on chronically exposed people using this assay.     

Enhanced immune response to the melanoma antigen gp100 using recombinant adenovirus-transduced dendritic cells

Glycoprotein 100 (gp100) is one of a series of well-characterized human melanoma-associated antigens expressed by most melanoma cells. Immunization of C57BL/6 mice with an adenovirus (Ad) vector encoding human gp100 (Adhgp100) has been shown to induce limited protective immunity against challenge with murine melanoma B16 cells. In the current study we determined whether gp100-specific immunity can be enhanced using bone-marrow-derived dendritic cells (DCs) transduced with Adhgp100 ex vivo. Subcutaneous injection of Adhgp100-infected DCs resulted in potent T-cell-mediated protective immunity and a greater than 80% reduction of established tumors when administered to B16 tumor-bearing hosts. Compared to direct injection of Adhgp100 vector alone, immunization with Adhgp100-infected DCs induced markedly greater antitumor activity. In vitro CTL analysis demonstrated that DC-Adhgp100 immunization activated both CD4(+) and CD8(+) CTLs, while no lytic activity was generated by vaccination with Adhgp100 alone. In vivo depletion of CD4(+) T cells, but not CD8(+) T cells, completely abrogated CTL activity, suggesting that Adhgp100-transduced DCs result in activation of both CD4(+) and CD8(+) CTLs via a CD4(+)-dependent mechanism. We speculate that this improved efficacy of Adhgp100-transduced DCs compared to direct immunization with Adhgp100 may be the result of direct DC-mediated CD4(+) T cell activation. These results emphasize the importance of CD4(+) T cells in the development of therapeutic antigen-specific cancer vaccines.     

β-defensin 2 as an adjuvant promotes anti-melanoma immune responses and inhibits the growth of implanted murine melanoma in vivo

β-defensin 2 is a small antimicrobial peptide of the innate immune system and has been thought to regulate anti-tumor immunity. However, little is known on whether β-defensin 2 could modulate melanoma-specific NK and T cell responses. In this study, we first cloned the murine β-defensin 2 gene by RT-PCR and generated the β-defensin 2 stably expressing B16 cells (B16-mBD2). Subsequently, we evaluated whether vaccination with irradiated B16-mBD2 could modulate the growth of implanted B16 cells and determined the potential mechanisms underlying the action of B16-mBD2 vaccine in modulating the growth of B16 tumors in C57BL/6. We found that vaccination with irradiated B16-mBD2, but not with control B16-p or parental B16, inhibited the development and progression of B16 tumors, and prolonged the survival of tumor-bearing mice. However, vaccination with irradiated B16-mBD2 failed to inhibit the development of B16 tumors in the CD4(+)- or CD8(+)-depleted recipients. Furthermore, vaccination with irradiated B16-mBD2 stimulated strong NK activity and promoted potent B16-specific CTL responses, accompanied by augmenting IFN-γ and IL-12, but not IL-4, responses in the recipient mice. Moreover, vaccination with irradiated B16-mBD2 promoted the infiltration of CD8(+) and CD4(+) T, NK cells and macrophages in the tumor tissues. These data suggest β-defensin 2 may act as a positive regulator, promoting anti-tumor NK and T cell responses in vivo. Therefore, β-defensin 2 may be used for the development of immunotherapy for the intervention of melanoma.