exposure to ionizing radiation generates several reactive oxygen species ( ros ) , like hydroxyl radical , hydrogen peroxide , aqueous electron , and superoxide in the aqueous medium . such ros have harmful effects on macromolecules such as lipids , proteins , and dna and damages cellular function , leading to multiple disorders and dysfunctions in the human body ( 1 , 2 ) . as several studies in the literature have indicated , radiation response is a multi - factorial scenario that depends on several parameters , such as the nuclear material content , cell reproduction , tissue and organ revival , and biological repair . from a biological viewpoint , it is important to consider how radiation response may moderate the responses of tissues and organs to gamma irradiation . from this aspect , genetic properties are highly crucial in most diseases and disorders , such as ataxia - telangiectasia ( at ) ( 3 ) , xeroderma pigmentosum ( 4 ) , and breast cancer ( 5 ) , and an important characteristic in the radiosensitivity of cells , tissues and organs ( 5 ) . approximately 10% of normal individuals in similar physical and environmental conditions exhibit incremented response to ionizing radiations ( 6 ) . increased radiosensitivity of breast cancer patients has been reported in several different studies ( 79 ) . hence , identifying a prognostic marker for radiotherapy is one of the main goals of the radiation biology and radiation protection field . if the personal complication risks of ionizing radiation are recognized , the risk could be reduced in the small ratio of highly sensitive people through dose reduction in patients and the defining of more limited rules in radiation protection regulations ( 10 ) . some origins of radiosensitivity , including physiological , genetic , and epigenetic sources , have been proposed in cancer patients and normal individuals ( 11 , 12 ) . several studies have marked that abo blood groups are associated with the risk of ischemic heart disease and developing severe manifestation of atherosclerosis ( 13 ) . results from the framingham study and other reports showed the occurrence of ischemic heart disease might be higher in subjects with blood group a ( 13 ) . in addition , patients with blood groups a or o are more often afflicted with pernicious anemia ( 14 ) . the incidences of gastric carcinoma ( 15 ) , peptic ulcer ( 16 ) , and ovarian cancer ( 5 ) are much more extensive in persons with blood types a , o , and b , respectively . nonetheless , it was explained that the abo blood group is an inherent characteristic ( 17 ) . thereafter , the alleles for the blood groups were recognized in the same place on chromosome 9 at 9q34.1q34.2 ( 18 ) . these findings demonstrated that one s blood group is a genetic trait . despite such investigations , a preliminary clinical study showed that the radiation response of type o patients suffering from carcinoma of the cervix is better than those of other blood groups ( 19 ) . meanwhile , an elevated frequency of micronuclei ( mn ) in the a blood group was reported in peripheral blood lymphocytes of normal individuals ( 20 ) . regarding these findings - and given the variation in radiosensitivity in the normal population - this study aimed to evaluate chromosomal radiosensitivity of peripheral blood lymphocytes in normal individuals with rh and rh factors . in this experimental study , informed consent was acquired from 50 healthy human volunteers ( 25 rh+ and 25 rh ) in the a blood group who ranged in age from 22 to 23 years old . all responders completed a questionnaire to provide information on their lifestyle and exposure to chemical and physical agents . having a history of known irradiation , smoking , drug treatment , and alcohol consumption were exclusion criteria . finally , samples were divided into two separate groups ( control and exposed blood samples ) . the aliquots of blood samples were exposed to gamma radiation of a low let co source ( theratone780 manufactured by canada ) at dose rate of 70 cgy / min , with source - to - sample distance ( ssd ) = 80 cm , a field size of 10  10 cm , and at room temperature . blood samples were irradiated with a total dose of 2 gy , and a vial of unexposed blood samples was kept as the control group . the cbmn assay was carried out using the standard technique proposed by earlier investigations ( 21 ) , with minor modifications ( 22 ) . hence , 0.5ml of peripheral blood samples were added to 4.5ml of a cell culture medium ( rpmi-1640 ) containing sodium bicarbonate supplemented with 10% fetal calf serum ( fcs ) , antibiotics , and 1% l - glutamine . one hundred microliters of phytohaemagglutinin ( pha , sigma ) was added to stimulate lymphocytes . forty - four hours after pha stimulation , cytochalasin - b ( cyt - b , sigma ) at a final concentration of 6g / ml was added , and binucleated lymphocytes were harvested after 72 h. the cells were then collected by centrifugation at 2,000 rpm for 10 min ( boecho u-320 r ) , and supernatant was decanted . two to three microliters of fresh hypotonic solution 0.075 m kcl was added to the solution remaining at the bottom of tubes and centrifuged at 1,200 rpm for 7 min . again , the supernatant was poured off , and 5ml of fixature including methanol : glacial acetic acid ( 6/1 ) were quickly mixed with solution at the bottom of the tubes . the induction of mn was evaluated using a double - blind score of 1000 binucleated cells ( bnc ) with a light microscope set to 40x magnification . independent - sample t - test was used to determine the statistical significance of the difference between rh and rh samples . in addition , a paired - samples t - test was used to analyze the difference between the control and exposed samples . the study was approved by the ethical committee of the faculty of medical sciences at babol university of medical sciences ( babol , iran ) . in this experimental study , informed consent was acquired from 50 healthy human volunteers ( 25 rh+ and 25 rh ) in the a blood group who ranged in age from 22 to 23 years old . all responders completed a questionnaire to provide information on their lifestyle and exposure to chemical and physical agents . having a history of known irradiation , smoking , drug treatment , and alcohol consumption were exclusion criteria . finally , samples were divided into two separate groups ( control and exposed blood samples ) . the aliquots of blood samples were exposed to gamma radiation of a low let co source ( theratone780 manufactured by canada ) at dose rate of 70 cgy / min , with source - to - sample distance ( ssd ) = 80 cm , a field size of 10  10 cm , and at room temperature . blood samples were irradiated with a total dose of 2 gy , and a vial of unexposed blood samples was kept as the control group . the cbmn assay was carried out using the standard technique proposed by earlier investigations ( 21 ) , with minor modifications ( 22 ) . hence , 0.5ml of peripheral blood samples were added to 4.5ml of a cell culture medium ( rpmi-1640 ) containing sodium bicarbonate supplemented with 10% fetal calf serum ( fcs ) , antibiotics , and 1% l - glutamine . one hundred microliters of phytohaemagglutinin ( pha , sigma ) was added to stimulate lymphocytes . forty - four hours after pha stimulation , cytochalasin - b ( cyt - b , sigma ) at a final concentration of 6g / ml was added , and binucleated lymphocytes were harvested after 72 h. the cells were then collected by centrifugation at 2,000 rpm for 10 min ( boecho u-320 r ) , and supernatant was decanted . two to three microliters of fresh hypotonic solution 0.075 m kcl was added to the solution remaining at the bottom of tubes and centrifuged at 1,200 rpm for 7 min . again , the supernatant was poured off , and 5ml of fixature including methanol : glacial acetic acid ( 6/1 ) were quickly mixed with solution at the bottom of the tubes . the induction of mn was evaluated using a double - blind score of 1000 binucleated cells ( bnc ) with a light microscope set to 40x magnification . independent - sample t - test was used to determine the statistical significance of the difference between rh and rh samples . in addition , a paired - samples t - test was used to analyze the difference between the control and exposed samples . the study was approved by the ethical committee of the faculty of medical sciences at babol university of medical sciences ( babol , iran ) . the results of this study showed an increased mean frequency of mn in binucleated cells after irradiation ( figure 1 ) . as table 1 shows , the mean values of mn in binucleated cells were 196  18.23 and 169  17.11 for rh and rh samples , respectively ( table 1 ) . the results indicated that the average mn is significantly higher in rh than in rh in the irradiated group ( p<0.001 ) ( table 1 ) . table 2 shows that the frequency of mn cells significantly increased in both rh and rh irradiated ( 2gy ) samples whereas the percentage of binucleated , trinucleated , and tetranucleated cells decreased after irradiation . the ndi value for the rh group was 1.81 and 1.39 before and after irradiation , respectively . for the rh type , the parameter declined from 1.85 to 1.40 following gamma irradiation . regarding the ndi in table 2 , approximately 20% of the radiotherapy patients showed a wide range of normal tissue reactions ( 23 ) . recognizing patients with high , moderate , or low radiosensitivity would help develop a good plan for the radiotherapy of patients with the highest cure rate in terms of the patient s individual adaptation ( 10 ) . the explanation of criteria that modify the total effects of ionizing radiation is one of the main subjects of research efforts in radiobiology . some studies have explained that a correlation exists between tumor response and the level of 8-oxo - dg in the urine of lung and breast cancer patients ( 23 ) . hence , several studies have been initiated to investigate whether radiosensitivity is an individualized subject in patients radiation response . the main purpose of this study was to investigate the role of rh in radiation response of healthy people . hoeller et al . showed that individual radiosensitivity measured by lymphocytes might be a good way to predict fibrosis in breast cancer patients after radiotherapy ( 24 ) . in the field of radiobiology , the cbmn cyt assay for pbl is a suitable bio - dosimetry device to measure in - vivo and in - vitro radiosensitivity and cancer reproducibility ( 25 ) . lymphocytes are chosen because of their easy availability , simple method of culture , and ease of sample collection . therefore , in our study , cbmn cyt assay as one of the standard techniques for genetic toxicology evaluation in human cells was selected to measure chromosomal aberrations in rh and rh healthy people . as expected , the average number of mn increased significantly after the 2gy gamma irradiation of lymphocyte cells . this result concurs with the earlier findings indicating a higher level of mn after gamma irradiation ( 21 , 26 ) . the current study showed that the mean frequency of mn in the rh group was roughly 16% higher than in the rh group . this result might be due to the association of rh alleles on chromosome 9 and particular alleles of genes responsible for dna double strand break repair . however , more molecular investigations need to evaluate more precisely the main reason for this event . indicated that the a blood group has more mn frequency compared to other blood types ( 20 ) . they showed that group a has a higher frequency of mn than did groups ab , b , and o ( 20 ) . in another study , they showed that left - handed breast cancer women are more radiosensitive than right - handed women ( 18 ) . the background mn frequency in the present study was 3.75  0.53 and 5.35  0.90 for the rh and rh groups , respectively . this value is in fair agreement with the cited value of iaea epr bio - dosimetry manual by international atomic energy agency ( 27 ) . regarding the iaea report , the background mn frequencies range from 0 to 40 per 1000 bn cells ( 27 ) . for the ndi counted prior to and after irradiation , the value decreased in both rh and rh groups after 2gy gamma irradiation , indicating a reduction in cell proliferation . however , no significant difference occurred between these two blood types after irradiation . as the present study indicated , a decrease yield of binucleated and polynucleated cells was observed after gamma irradiation . in contrast , the frequency of mononucleated cells increased after gamma irradiation . because carrying out standard cytokinesis blocked micro - nuclei protocol was time consuming , choosing a larger study population the present study suggested that chromosomal radiosensitivity of lymphocytes in normal individuals with rh factor is higher than their rh counterparts . this finding revealed that the rh factor can be considered one of the hereditary traits affecting individuals radiosensitivity and can be a valuable item in radiation protection regulations . however , further in - vivo and in - vitro studies are needed for validation .
introductionradiosensitivity is an inherent trait , associated with a raised reaction to ionizing radiation on the human body . in radiotherapy and radiation protection fields , 
 individualization of the patient s treatment is one of the main topics . with the goal of determining biomarkers capable of anticipating normal tissue side reactions , 
 we studied the association between the rh factor and radiosensitivity.methodsthis experimental study was carried out from january to june 2014 among 50 normal responders with a blood group ( 25rh+ and 25rh ) between the ages of 22 and 23 in babol , iran . 
 human peripheral blood samples were taken from subjects and , using cbmn assay , the biological effects of gamma irradiation , including the frequency of micronuclei ( mn ) and nuclear division index ( ndi ) , were measured . 
 a data analysis was performed using spss version 18 to determine the independent and paired samples t-tests.resultsa significant increment occurred in the frequency of mn in group rh+ ( 196  18.23 ) compared with rh- ( 169  17.11 ) following irradiation ( p<0.001).conclusionsthe rh factor might be a predicting marker in an individual s radiosensitivity to ionizing radiations . 
 however , we believe that additional investigations are needed to prove this hypothesis .