CD103+ regulatory T cells underlie resistance to radio-immunotherapy and impair CD8+ T cell activation in glioblastoma.

Glioblastomas are aggressive primary brain tumors with an inherent resistance to T cell-centric immunotherapy due to their low mutational burden and immunosuppressive tumor microenvironment. Here we report that fractionated radiotherapy of preclinical glioblastoma models induce a tenfold increase in T cell content. Orthogonally, spatial imaging mass cytometry shows T cell enrichment in human recurrent tumors compared with matched primary glioblastoma. In glioblastoma-bearing mice, α-PD-1 treatment applied at the peak of T cell infiltration post-radiotherapy results in a modest survival benefit compared with concurrent α-PD-1 administration. Following α-PD-1 therapy, CD103+ regulatory T cells (Tregs) with upregulated lipid metabolism accumulate in the tumor microenvironment, and restrain immune checkpoint blockade response by repressing CD8+ T cell activation. Treg targeting elicits tertiary lymphoid structure formation, enhances CD4+ and CD8+ T cell frequency and function and unleashes radio-immunotherapeutic efficacy. These results support the rational design of therapeutic regimens limiting the induction of immunosuppressive feedback pathways in the context of T cell immunotherapy in glioblastoma.

A rectal metastasis of an unknown lobular breast carcinoma and its management.

Breast cancer is the most common cancer in women but gastro- intestinal metastases of breast cancer are rare. They can occur years after the diagnosis or at the diagnosis of breast cancer. We report the case of a patient complaining of dyschesia, tenesmus and anal incontinence leading to the discovery of a rectal metastasis of an unknown breast neoplasia. Given the oligo-metastatic condition, multidisciplinary and aggressive management was the chosen therapy.

Adenocarcinoma of the Uterine Cervix Shows Impaired Recruitment of cDC1 and CD8+ T Cells and Elevated ß-Catenin Activation Compared with Squamous Cell Carcinoma.

PURPOSE: Adenocarcinoma of the uterine cervix is the second most common type of cervical cancer after squamous cell carcinoma (SCC). Although both subtypes are treated similarly, patients with adenocarcinoma have a worse prognosis. In this study, immunologic features of the tumor microenvironment in these two subsets were pursued with potential therapeutic implications. EXPERIMENTAL DESIGN: The immune microenvironment of primary tumors and nonmetastatic tumor-draining lymph nodes (TDLN) was compared between patients with cervical adenocarcinoma (n = 16) and SCC (n = 20) by polychromatic flow cytometry and by transcriptional profiling of the primary tumors (n = 299) using publicly available data from The Cancer Genome Atlas (TCGA). RESULTS: Flow cytometric analyses revealed intact T-cell differentiation in TDLNs, but hampered effector T-cell trafficking to the primary tumors in adenocarcinoma, as compared with SCC. TCGA analysis demonstrated higher expression of chemokines involved in effector T-cell homing (CXCL9/10/11) in SCC primary tumors as compared with adenocarcinoma primary tumors, which was highly correlated to a transcriptional signature for type I conventional dendritic cells (cDC1). This was consistent with elevated frequencies of CD141/BDCA3+cDC1 in primary tumor SCC samples relative to adenocarcinoma and correspondingly elevated levels of CXCL9 and CXCL10 in 24-hour ex vivo cultures. Hampered cDC1 recruitment in adenocarcinoma was in turn related to lower transcript levels of cDC1-recruiting chemokines and an elevated ß-catenin activation score and was associated with poor overall survival. CONCLUSIONS: Our data have identified an opportunity for the investigation of potentially novel therapeutic interventions in adenocarcinoma of the cervix, that is, ß-catenin inhibition and cDC1 mobilization.

Treatment of the edentulous atrophic maxilla using zygomatic implants: evaluation of survival rates over 5-10 years.

The aim of this retrospective observational cohort study was to analyse and report the 5-10-year survival rates of endosseous zygomatic implants used in the rehabilitation of the atrophic maxilla. Forty-three consecutive zygomatic implant placements in 25 patients were evaluated over a 5-10-year period. All zygomatic implant surgery was carried out under general anaesthesia. Nobel Biocare zygomatic machined-surface implants were used, and placement was undertaken using the modified sinus slot method. The main outcome measures and determinants for success were survival of the restored implants and the proportion of originally planned prostheses delivered to patients. Of the 25 patients treated, 12 were male and 13 were female; 19 were non-smokers, and the mean age at time of surgery was 64 years. Patients were treatment-planned for implant-retained bridgework, a removable prosthesis retained by fixed cast gold or milled titanium beams, or magnet-retained removable prostheses. A combination of zygomatic and conventional implants was used in all but one patient. In this study it was shown that the overall success rate for zygomatic implants was 86%, with six of the implants either failing to integrate or requiring removal due to persistent infection associated with the maxillary sinus. All patients received their planned prosthesis, although in six cases the method of retention required modification. This study illustrates that zygomatic implants are a successful and important treatment option when trying to restore the atrophic maxilla, with the potential to avoid additional augmentation/grafting procedures and resulting in a high long-term success rate.

Impact des legumineuses fourrageres et/ou de couverture sur la biodiversite floristique au Nord-Cameroun

Une etude synchronique a ete menee dans un dispositif experimental mis en place en juin 1994 en zone soudano-sahelienne du Cameroun et comprenant quatre types de jacheres ameliorees avec des legumineuses a usages multiples. Initialement concu pour mesurer l'impact de la coupe et de la pature sur le rendement grainier de Calopogonium mucunoides; Stylosanthes hamata; et Cajanus cajan; ce dispositif a ete laisse en jachere de 1995 a mai 2000. L'evolution de la flore et de la production de biomasse herbacee 6 ans apres abandon ont ete etudiees en utilisant la methode phytosociologique sigmatiste et l'analyse structurale par la methode des points quadrats. L'analyse de la production de biomasse a ete faite par la methode des coupes totales. Les resultats obtenus montrent que les legumineuses utilisees permettent une augmentation significative de la biomasse herbacee des jacheres. Par leur aptitude a coloniser rapidement l'espace; elles concourent a l'appauvrissement de la biodiversite floristique. Ce caractere nettoyant peut etre utilise pour lutter contre la persistance des adventices dans les parcelles agricoles. La litiere accumulee est plus importante dans les jacheres a Calopogonium mucunoides; et dans celles ayant comme antecedent l'association Cajanus cajan / Zea mays. Des analyses ulterieures permettront de mettre en evidence l'impact de ces legumineuses sur la fertilite des sols de la region

A method to differentiate between the levels of ESR signals induced by sunlight and by ionizing radiation in teeth from atomic bomb survivors.

Electron spin resonance (ESR, or electron paramagnetic resonance, EPR) analysis of tooth enamel is an effective method for the retrospective estimation of individual radiation doses. One problem with this technique is that the observed ESR signal may include a contribution from ultraviolet (UV) light exposure from sunlight, especially in front teeth. Thus there has been a need to find ways to estimate the UV-light effect in the total signal so that the net ESR dose from ionizing radiation can be determined. To examine this issue, we measured 96 teeth of various types, but with buccal and lingual parts measured separately, from a control group of atomic bomb survivors (estimated dose <5 mGy). We found that, except for molars, the mean ESR-estimated dose for the buccal halves was, on average, nearly twice that from the lingual side, which indicates that the UV-light-induced lingual dose equals the difference between the two halves. Using these corrections for UV-light exposure to front teeth that had been exposed to both ionizing radiation and UV light, it was found that the estimated radiation doses closely approximated the previously estimated ESR dose to molars from the same donors or the estimated dose arrived at with cytogenetic methods. We concluded that, when using ESR to estimate radiation dose, measuring molars is the first choice, but if only front teeth are available, separate measurements to the buccal and lingual parts can provide an estimation of the mean UV-light contribution to the ESR-determined dose.

Clonally expanded T-cell populations in atomic bomb survivors do not show excess levels of chromosome instability.

Radiation-induced genomic instability has been studied primarily in cultured cells, while in vivo studies have been limited. One major obstacle for in vivo studies is the lack of reliable biomarkers that are capable of distinguishing genetic alterations induced by delayed radiation effects from those that are induced immediately after a radiation exposure. Here we describe a method to estimate cytogenetic instability in vivo using chromosomally marked clonal T-cell populations in atomic bomb survivors. The basic idea is that clonal translocations are derived from single progenitor cells that acquired an aberration, most likely after a radiation exposure, and then multiplied extensively in vivo, resulting in a large number of progeny cells that eventually comprise several percent of the total lymphocyte population. Therefore, if chromosome instability began to operate soon after a radiation exposure, an elevated frequency of additional but solitary chromosome aberrations in clonal cell populations would be expected. In the present study, six additional translocations were found among 936 clonal cells examined with the G-band method (0.6%); the corresponding value with multicolor FISH analysis was 1.2% (4/333). Since these frequencies were no higher than 1.2% (219/17,878 cells), the mean translocation frequency observed in control subjects using the G-band method, it is concluded that chromosome instabilities that could give rise to an increased frequency of persisting, exchange-type aberrations were not commonly generated by radiation exposure.

Tea tree oil: in vitro efficacy in otitis externa.

OBJECTIVE: The purpose of this study was to determine the susceptibility of organisms causing otitis externa (OE) to the essential oil of Melaleuca alternifolia, or tea tree oil (TTO). METHODS: Fifty-seven swabs were taken from the ears of 52 patients with OE for culture and sensitivity. A broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of TTO for each organism. RESULTS: In 51 percent of the swabs taken, pathogenic organisms were cultured. Of these cultures 71 percent, both bacteria and yeast, were susceptible to TTO 2 percent or less. The only organism showing resistance to TTO was Pseudomonas aeruginosa; however 25 percent of these bacteria were sensitive. CONCLUSION: Tea tree oil may have a role to play in the treatment of OE. However, more work needs to be done to enhance the anti-pseudomonal effect and to assess ototoxicity.

Immunotherapy for advanced renal cell cancer.

BACKGROUND: The course of advanced renal cell carcinoma is extremely variable, ranging from spontaneous remission to disease progression refractory to chemotherapy. Immunotherapy has held promise of improved outcomes based on uncontrolled studies and randomized controlled trials generally limited by small size and low power. OBJECTIVES: To evaluate immunotherapy for advanced renal cell carcinoma by comparing: (1) high dose interleukin-2 to other options and (2) interferon-alfa to other options. The primary outcome of interest was overall survival at one year, with remission as the main secondary outcome of interest. SEARCH STRATEGY: A systematic search of the CENTRAL, MEDLINE, and EMBASE databases was conducted for the period 1966 through end of December 2003. Handsearches were made of the proceedings of the periodic meetings of the American Urologic Association, the American Society of Clinical Oncology, ECCO - the European Cancer Conference, and the European Society of Medical Oncology for the period 1995 to June 2004. SELECTION CRITERIA: Randomized controlled trials that selected (or stratified) patients with advanced renal cell carcinoma, utilized an immunotherapeutic agent in at least one study arm, and reported remission or survival by allocation. Fifty-three identified studies involving 6117 patients were eligible and all but one reported remission; 32 of these studies reported the one-year survival outcome. DATA COLLECTION AND ANALYSIS: Two reviewers independently abstracted each article by following a prospectively designed protocol. Dichotomous outcomes for treatment remission (partial plus complete) and for deaths at one year were used for the main comparisons. Survival hazard ratios were also used for studies of interferon-alfa versus controls, and for two randomized studies of the value of initial nephrectomy prior to interferon-alfa in fit patients with metastases detected at the time of diagnosis. MAIN RESULTS: Combined data for a variety of immunotherapies gave an overall chance of partial or complete remission of only 12.9% (99 study arms), compared to 2.5% in 10 non-immunotherapy control arms, and 4.3% in two placebo arms. Twenty-eight percent of these remissions were designated as complete (data from 45 studies). Median survival averaged 13.3 months (range by arm, 6 to 27+ months). The difference in remission rate between arms was poorly correlated with the difference in median survival so that remission rate is not a good surrogate or intermediate outcome for survival for advanced renal cancer. We were unable to identify any published randomized study of high-dose interleukin-2 versus a non-immunotherapy control, or of high-dose interleukin-2 versus interferon-alfa reporting survival. It has been established that reduced dose interleukin-2 given by intravenous bolus or by subcutaneous injection provides equivalent survival to high dose interleukin-2 with less toxicity. Results from four studies (644 patients) indicate that interferon-alfa is superior to controls (OR for death at one year = 0.56, 95% confidence interval 0.40 to 0.77). Using the method of Parmar 1998, the pooled overall hazard ratio for death was 0.74 (95% confidence interval 0.63 to 0.88). The weighted average median improvement in survival was 3.8 months. T he optimal dose and duration of interferon-alfa remains to be elucidated. The addition of a variety of enhancers, including lower dose intravenous or subcutaneous interleukin-2, has failed to improve survival compared to interferon-alfa alone. Two recent randomized studies have examined the role of initial nephrectomy prior to interferon-alfa therapy in highly selected fit patients with metastases at diagnosis and minimal symptoms: despite minimal improvement in the chance of remission, both studies of up-front nephrectomy improved median survival by 4.8 months over interferon-alfa alone. Recent studies have been examining anti-angiogenesis agents. A landmark study of bevacizumab, an anti-vascular endothelial growth factor antibody, was associated with significant prolongation of the time to progression of disease when given at high dose compared to low-dose or placebo therapy though frequency of remissions or survival were not improved. AUTHORS' CONCLUSIONS: interferon-alfa provides a modest survival benefit compared to other commonly used treatments and should be considered for the control arm of future studies of systemic agents. In fit patients with metastases at diagnosis and minimal symptoms, nephrectomy followed by interferon-alfa gives the best survival strategy for fully validated therapies. The need for more effective specific therapy for this condition is apparent.

Human fetuses do not register chromosome damage inflicted by radiation exposure in lymphoid precursor cells except for a small but significant effect at low doses.

Human fetuses are thought to be highly sensitive to radiation exposure because diagnostic low-dose X rays have been suggested to increase the risk of childhood leukemia. However, animal studies generally have not demonstrated a high radiosensitivity of fetuses, and the underlying causes for the discrepancy remain unidentified. We examined atomic bomb survivors exposed in utero for translocation frequencies in blood lymphocytes at 40 years of age. Contrary to our expectation of a greater radiosensitivity in fetuses than in adults, the frequency did not increase with dose except for a small increase (less than 1%) at doses below 0.1 Sv, which was statistically significant. We interpret the results as indicating that fetal lymphoid precursor cells comprise two subpopulations. One is small in number, sensitive to the induction of both translocations and cell killing, but rapidly diminishing above 50 mSv. The other is the major fraction but is insensitive to registering damage expressed as chromosome aberrations. Our results provide a biological basis for resolving the long-standing controversy that a substantial risk of childhood leukemia is implicated in human fetuses exposed to low-dose X rays whereas animal studies involving mainly high-dose exposures generally do not confirm it.

Prediction of clonal chromosome aberration frequency in human blood lymphocytes.

We recently conducted a large-scale screening for clonal aberrations among atomic bomb survivors and proposed a model for the gross clonal composition of blood lymphocytes. Here we show an application of the model indicating that the number, m,of clones detectable by cytogenetic methods in an individual is predictable by the equation m= (1.8 + 6.4FG) x FP x n/500, where FG represents the estimated translocation frequency in the 46 chromosome set, FP is the observed translocation frequency with FISH or other methods, and nis the number of cells examined. Application of the equation to the results of seven other reports gave close agreement between the observed and calculated numbers of clones. Since the model assumes that clonal expansion is ubiquitous, and any translocation can be the constituent of a clone detectable by cytogenetic means, the vast majority of observed clonal expansions of these somatic cells are likely the result of random-hit events that are not detrimental to human health. Furthermore, since our model can predict the majority of clonal aberrations among Chernobyl workers who were examined 5-6 years after irradiation, clonal expansion seems to occur primarily within a few years after exposure to radiation, most likely being coupled with the process of recovery from radiation-induced injury in the lymphoid and hematopoietic systems.

Estimating the number of hematopoietic or lymphoid stem cells giving rise to clonal chromosome aberrations in blood T lymphocytes.

Quantifying the proliferative capacity of long-term hematopoietic stem cells in humans is important for bone marrow transplantation and gene therapy. Obtaining appropriate data is difficult, however, because the experimental tools are limited. We hypothesized that tracking clonal descendants originating from hematopoietic stem cells would be possible if we used clonal chromosome aberrations as unique tags of individual hematopoietic stem cells in vivo. Using FISH, we screened 500 blood T lymphocytes from each of 513 atomic bomb survivors and detected 96 clones composed of at least three cells with identical aberrations. The number of clones was inversely related to their population size, which we interpreted to mean that the progenitor cells were heterogeneous in the number of progeny that they could produce. The absolute number of progenitor cells contributing to the formation of the observed clones was estimated as about two in an unexposed individual. Further, scrutiny of ten clones revealed that lymphocyte clones could originate roughly equally from hematopoietic stem cells or from mature T lymphocytes, thereby suggesting that the estimated two progenitor cells are shared as one hematopoietic stem cell and one mature T cell. Our model predicts that one out of ten people bears a non- aberrant clone comprising >10% of the total lymphocytes, which indicates that clonal expansions are common and probably are not health-threatening.

Effect of cavity margin shavings to ensure completeness of excision on local recurrence rates following breast conserving surgery.

AIMS: The presence of residual disease at the excision margin after breast conserving surgery is the most important risk factor for local recurrence. One method for assessing tumour margin involvement is to take shavings from the wall of the resulting cavity following wide excision of the lesion. METHODS: We have reviewed our experience of shaving the margin of the cavity as our method to ensure completeness of excision. RESULTS: Of 351 patients treated with breast conservation 61 patients had residual disease in the cavity margin biopsies. Younger age, axillary lymph node status, multi-focal tumours and high grade tumours were significantly correlated with margin involvement. In patients who had clear margins eight patients (2.8%) had developed a local recurrence at follow-up of 55 months (25-89 months). CONCLUSIONS: In our hands the use of cavity margin shavings allows us to achieve an acceptable rate of local control.

A review of cochlear implantation in mitochondrial sensorineural hearing loss.

OBJECTIVE: Mitochondrial sensorineural hearing loss (SNHL) may be nonsyndromic (occurring in isolation), associated with the A1555G mutation in the MTRNR1 gene. Mitochondrial SNHL may also be syndromic, associated with the A3243G point mutation in the MTTL1 gene. In syndromic cases-mitochondrial encephalopathy, lactic acidosis, and strokelike episodes (MELAS), maternally inherited diabetes and deafness, Kearns-Sayre syndrome, and chronic progressive external ophthalmoplegia-the SNHL compounds already existing disabilities. The genetic basis for mitochondrial SNHL and postulated sites of pathologic changes are discussed. DATA SOURCES: Sources used were relevant clinical and basic science publications. STUDY SELECTION: A search of the entire databases of Medline and Web of Science, using various subject headings and free-text terms, was used to identify patients with mitochondrial disease having cochlear implants. DATA EXTRACTION: The data from publications were critically reviewed and tabulated to assess implantation outcomes. DATA SYNTHESIS: The data were not amenable to formal meta-analysis or valid data summarization, other than descriptive statistics. CONCLUSIONS: There is an increasing awareness of the prevalence of mitochondrial SNHL and its progressive nature. High-risk candidates warrant genetic testing and family screening. Correlating the data for mitochondrial SNHL as a treatable entity is important, and the authors present an overview of these patients successfully rehabilitated by cochlear implantation.

The role of lymph node sampling and radiotherapy in the management of the axilla in early breast cancer.

Management of the axilla in early breast cancer is an issue of ongoing debate. We reviewed our experience in 312 patients who underwent axillary lymph node sampling between 1994 and 1998, of whom 81 patients (24%) had axillary lymph node metastasis. There have been two axillary recurrences, one associated with local recurrence to the breast and one presenting with distant metastasis. There were no patients with isolated axillary disease as their only site of recurrence and no axillary failures in the node-positive group treated with axillary sampling and radiotherapy. Axillary lymph node sampling effectively stages the axilla. This can safely be followed by radiotherapy to the axilla in case of lymph node metastasis. Axillary lymph node sampling forms a sound basis to develop new techniques, such as sentinel lymph node biopsy currently investigated by ongoing trials.

Detection of stable chromosome aberrations by FISH in A-bomb survivors: comparison with previous solid Giemsa staining data on the same 230 individuals.

PURPOSE: To evaluate the relative abilities of the solid Giemsa staining (conventional) and fluorescence in situ hybridization (FISH) methods in the detection of stable chromosome aberrations in the peripheral blood lymphocytes of A-bomb survivors. MATERIALS AND METHODS: Lymphocytes from a total of 230 A-bomb survivors for whom prior chromosome aberration data had been obtained by the conventional method were recently examined afresh using FISH in which chromosomes 1, 2 and 4 were painted with composite probes. RESULTS: It was found that the early use of the solid Giemsa staining method had allowed the detection of translocations with a mean frequency of 73% of the value for the genome-equivalent translocation frequency (F(G)) that was now obtained using FISH. The disparity may at least in part be due to the reciprocal exchange of seemingly identical amount of chromosome material; such exchanges can escape detection by the conventional method but can be readily identified using FISH. CONCLUSION: It has previously been established that the conventional method can detect about 20% of radiation-induced translocations as abnormal monocentric chromosomes. Present results indicate that an additional 50% can be detected if proper karyotyping is conducted and the remaining 30% are not likely to be detected unless FISH or banding methods are used. Thus, solid Giemsa staining accompanied by karyotyping may not be quite as unsuitable as is generally assumed for retrospective biodosimetry analyses, which deal mainly with stable aberrations.

Stable chromosome aberrations in atomic bomb survivors: results from 25 years of investigation.

Frequencies of stable chromosome aberrations from more than 3,000 atomic bomb survivors were used to examine the nature of the radiation dose response. The end point was the proportion of cells with at least one translocation or inversion detected in Giemsa-stained cultures of approximately 100 lymphocytes per person. The statistical methods allow for both imprecision of individual dose estimates and extra-binomial variation. A highly significant and nonlinear dose response was seen. The shape of the dose response was concave upward for doses below 1.5 Sv but exhibited some leveling off at higher doses. This curvature was similar for the two cities, with a crossover dose (i.e. the ratio of the linear coefficient to the quadratic coefficient) of 1.7 Sv (95% CI 0.9, 4). The low-dose slopes for the two cities differed significantly: 6.6% per Sv (95% CI 5.5, 8.4) in Hiroshima and 3.7% (95% CI 2.6, 4.9) in Nagasaki. This difference was reduced considerably, but not eliminated, when the comparison was limited to people who were exposed in houses or tenements. Nagasaki survivors exposed in factories, as well as people in either city who were outside with little or no shielding, had a lower dose response than those exposed in houses. This suggests that doses for Nagasaki factory worker survivors may be overestimated by the DS86, apparently by about 60%. Even though factory workers constitute about 20% of Nagasaki survivors with dose estimates in the range of 0.5 to 2 Sv, calculations indicate that the dosimetry problems for these people have little impact on cancer risk estimates for Nagasaki.

Organ doses from radiation therapy in atomic bomb survivors.

Previous surveys of radiation therapy among the Life Span Study (LSS) population at the Radiation Effects Research Foundation (RERF) revealed that 1,670 (1.4%) of the LSS participants received radiation treatments before 1984. The data on therapeutic radiation doses are indispensable for studying the relationship between radiation treatments and subsequent cancer occurrences. In this study, the radiation treatments were reproduced experimentally to determine the scattered radiation doses. The experiments were conducted using a female human phantom and various radiation sources, including a medium-voltage X-ray machine and a (60)Co gamma-ray source. Doses were measured using thermoluminescence dosimetry and ionization chambers. Radiation doses were determined for the salivary glands, thyroid gland, breast, lung, stomach, colon, ovary and active bone marrow. The results have been used for documenting the organ doses received by patients in previous surveys. The contribution of therapeutic irradiation to the occurrence of chromosome aberrations was studied using data on doses to active bone marrow from both radiation treatments and atomic bomb exposures in 26 RERF Adult Health Study participants. The results suggest that radiation treatments contributed to a large part of their frequencies of stable-type chromosome aberrations. The therapeutic radiation doses determined in the present study are available for investigating the effects of therapeutic irradiation on the subsequent primary cancers among atomic bomb survivors who received radiation treatments.

The F value for chromosome aberrations in atomic bomb survivors does not provide evidence for a primary contribution of neutrons to the dose in Hiroshima.

Brenner and Sachs (Radiat. Res. 140, 134-142, 1994) proposed that the ratio of interchromosomal to intrachromosomal exchanges, termed the F value, can be a cytogenetic fingerprint of exposure to radiations of different linear energy transfer (LET). Using published data, they suggested that F values are over 10 for low-LET radiations and approximately 6 for high-LET radiations. Subsequently, as F values for atomic bomb survivors were reported to be around 6, Brenner suggested that the biological effects of atomic bomb radiation in Hiroshima are due primarily to neutrons. However, the F values used for the survivors were means from individuals exposed to various doses. As the F-value hypothesis predicts a radiation fingerprint at low doses, we analyzed our own data for the survivors in relation to dose. G-banding data for the survivors showed F values varying from 5 to 8 at DS86 doses of 0.2 to 5 Gy in Hiroshima and around 6 in Nagasaki with no evidence of a difference between the two cities. The results are consistent with our in vitro data that the F values are invariably around 6 for X and gamma rays at doses of 0.5 to 2 Gy as well as two types of fission-spectrum neutrons at doses of about 0.2 to 1 Gy. Thus, apart from a possible effect at even lower doses, current data do not provide evidence to support the proposition that the biological effects of atomic bomb radiation in Hiroshima are caused mainly by neutrons.