obstructive sleep apnoea syndrome ( osas ) is a highly prevalent disease and is recognized as a major public health burden . osas is characterized by repeated events of partial or complete upper airway obstruction during sleep that lead to disruption of normal ventilation , hypoxemia , and sleep fragmentation . although the basic mechanisms mediating this association are likely multifactorial and remain to be fully elucidated , the cumulative burden of a chronic and low - grade systemic inflammation has emerged as the most likely contributor to the occurrence and magnitude of osas associated morbidity [ 14 ] . accumulating evidence in the past decade has corroborated the close association between osas , inflammation and various cardiovascular morbidities [ 5 , 6 ] . sleep is characterized by a specific regulation of the endocrine and autonomic nervous system , and thereby sleep is supposed to exert a systemic control over immune function [ 7 , 8 ] . osas is involving various immune cells , particularly t lymphocytes [ 9 , 10 ] . activation of t lymphocytes is among the crucial steps leading to the release of inflammatory mediators and adhesion molecules . t cells play a significant role in atherogenesis and plaque development via cytokine production and by directly contributing to vascular injury . in brief , investigating how this breathing disorder modulates immune responses may facilitate understanding the pathogenesis of osas in relation with its complications . alberti et al . found a prevailing activation of the th1-type cytokine pattern in osas patients by measuring plasma cytokine levels in osas patients . conversely , dyugovskaya et al . reported a shift in th1/th2 cytokine expression towards th2 dominance in patients with osas . in contrast , dimitrov et al . revealed that , compared with wakefulness , early nocturnal sleep induced a shift in the th1/th2 cytokine balance towards increased th1 activity , as indicated by an increased ratio of ifn-/il-4 producing t helper cells . however , the th1 shift was only of moderate size and replaced by th2 dominance during late sleep . to date , only a few paper has explored the th1/th2 balance in osas patients with incompatible results . there has recently been a minirevolution in the basic understanding of immunology following the discovery of two new subsets of t helper cells , t regulatory ( treg ) and th17 , which have opposite effects on autoimmunity and inflammation . th17 cells expressing retinoic acid related orphan receptor t ( rort ) play critical roles in the development of autoimmunity and allergic reactions by producing il-17 and il-6 . th17 cell is a key effector in the immune response and play critical roles in the development of autoimmunity by producing il-17 and , to a lesser extent , tnf- and il-6 . while treg cells expressing the forkhead / winged helix transcription factor ( foxp3 ) orchestrate the overall immune response and play a role in maintaining peripheral immune tolerance by contact - dependent suppression or releasing anti - inflammatory cytokines , such as interleukin ( il)-10 and transforming growth factor ( tgf)-1 and regulating the activity of the effector t cells . therefore , the th17/treg balance may control the development of autoimmunity and inflammation , and th17/treg imbalance is proved to be wide existed in human cancer , inflammatory and autoimmune diseases [ 1417 ] . therefore , we hypothesize that circulating treg / th17 imbalance may also present in osas patients , which is related with systemic inflammation and important in the pathogenesis of osas . to the best of our knowledge , a possible role for the th17/treg axis in osas has never been elucidated in osas . thus , the purpose is to test the hypothesis that the balance of th17 and treg frequencies in the peripheral circulation is disturbed in patients with varying degrees of osas . we evaluated plasma levels of th17- and treg - related cytokines and mrna expression of relevant transcription factors ( rort and foxp3 ) in peripheral blood monouclear cells ( pbmc ) . as a sensitive marker of inflammation , c - reactive protein ( crp ) is believed to be both a by - product and a mediator of the low - grade inflammation that occurs in osas . therefore , we explored the potential correlation of th17/treg imbalance with serum crp level and the severity of osas . consecutive men ( age 18 and < 70 years ) with newly confirmed osas by overnight polysomnography ( psg ) were initially recruited . all of them had been referred to the sleep disorders center , 3rd affiliated hospital of sun yat - sen university between jan . 2011 , with symptoms suggesting sleep related breathing disorders and had never been previously diagnosed or treated for osas . patients with a history of chronic or recent ( 1 month ) clinically significant infectious or inflammatory condition including asthma , trauma , vaccination , any invasive medical / surgical ( 3 months ) , or dental ( 1 month ) procedure were eliminated . patients with morbid obesity ( body mass index ( bmi ) > 35  kg / m ) , hypertension , coronary artery disease , heart failure , a history of stroke , diabetes mellitus , chronic obstructive or restrictive pulmonary disease , chronic renal disease , dyslipidemias , or pharmacologically treated depression were ineligible for the study . current smokers and exsmokers who smoked within 12 months before the start of current study were excluded . patients with sleep disorders such as upper airway resistance syndrome , central sleep apnea syndrome , periodic limbs movement , or narcolepsy were also removed from final analysis . control subjects were nonsmoking healthy subjects who had an ahi lower than 5 and no complaint of sleep apnea . control subjects were matched to osas patients for gender ( only male ) , age ( within 4 years ) , and bmi ( within 15% ) . except for possible obesity , all control subjects had a normal physical examination and laboratory tests . all subjects completed a standardized questionnaire including the epworth sleepiness scale ( ess ) score , demographic data , and clinical history . the study was approved by the institutional review board of the institutional review board of sun yat - sen university . anthropometric data ( age , bmi , neck circumferences ) along with daytime habits , such as smoking or exercise , were recorded . bmi , a statistical measurement that compares a person 's weight and height , was calculated as weight in kilograms divided by the height in meters squared . sleepiness was evaluated by ess . to exclude any respiratory or cardiovascular disease , spirometric evaluation , arterial blood gas analysis while the patient breathed room air , chest radiograph , and resting 12-lead electrocardiogram were conducted . all data were extracted from the medical records using a specially designed case report form ( crf ) . then the data were double - entered manually into a microsoft excel master sheet to build our database . subjects underwent an overnight polysomnography ( psg ) with the embla - monet 32 sleep system ( embla , usa ) which consisted of recording for eeg , electrooculography , electromyography , ecg , nasal pressure transducer , thermistor for nasal airflow , thoracic and abdominal impedance belts , pulse oximetry , tracheal microphone for snoring , and sensors for leg and sleep position . psg recordings were manually scored by a single registered technologist as described previously [ 1921 ] . apnea was defined as the pause of airflow at the nose and mouth lasting for > 10  s. hypopnea was defined as a decrease of 30% in thoracoabdominal motion associated with a fall in baseline oxygen saturation of > 4% . the apnea - hypopnea index ( ahi ) was expressed as the number of episodes of apnea and hypopnea per hour of total sleep time ( tst ) . the severity of hypoxia was assessed by calculating the lowest oxygen saturation ( nadir sao2 ) and the percentage of tst spent with oxygen saturation at sao2 < 90% . osas subjects were classified into two groups according to their apnea - hypopnea frequency as mild to moderate osas ( ahi > 5  30 ) , and severe osas ( ahi > 30 ) . blood samples were obtained the morning after polysomnography , between 08:00 and 09:00 following an overnight fast . the 1520  ml of peripheral blood ( pb ) samples were collected into collection tubes containing 0.2  ml sodium heparin . pbmcs were prepared by ficoll - hypaque density centrifugation for analysis of flow cytometry and real - time quantitative polymerase chain reaction ( rt - qpcr ) . plasma was obtained after centrifugation and stored at 80c for the measurement of the cytokines . pbmcs were suspended at a density of 2  10 cells / ml in complete culture medium ( rpmi 1640 supplemented with 100  u / ml penicillin , 100  g / ml streptomycin , 2  mm glutamine , 10% heat inactivated fetal calf serum ; gibco brl , gaithersburg , md ) . cultures were stimulated with phorbol myristate acetate ( pma , 50  ng / ml ) plus ionomycin ( 1  m ) for 4  h in the presence of monensin ( 500  ng / ml ; all from alexis biochemicals , san diego , ca ) . the incubator was set at 37c under a 5% co2 environment . after 4  h of culture , the contents of the well were transferred to 5-ml sterile tubes and centrifuged at 1500  rpm for 5  min . for the th17 analysis , the cells were incubated with phycoerythrin ( pe ) antihuman cd4 ( ebioscience , san diego , ca ) at 4c for 20  min . for the treg analysis , the cells were incubated with fluorescein isothiocyanate ( fitc ) anti - human cd4 and pe anti - human cd25 at 4c for 30  min . following surface staining , the cells were fixed and permeabilized according to the manufacturer 's instructions , and then stained with fitc anti - human il-17a for th17 detection or percp - cy5.5 ( pc61.5 ; ebioscience ) anti - human foxp3 for treg detection . stained cells were analysed by flow cytometric analysis using a facscan flow cytometer ( becton dickinson ) equipped with cellqest pro 5.2 software ( bd biosciences , usa ) . total rna was extracted from the pbmcs with trizol extraction ( invitrogen , carlsbad , ca , usa ) according to the manufacturer 's instructions , cdna was synthesized using random hexamer primers and rnase h - reverse transcriptase ( invitrogen ) . the following primer pairs were used : foxp3 : f : 5-cacgcatgtttgccttcttcaga-3 , r : 5-gtagggttggaacacctg ctggg-3 , and rort : f : 5-gcaatggaagtggtgctggtt-3 , r : 5-aggatgctttggcgatgagt c-3. primers were entered into ncbi blast database to ensure that it was specific for the target mrna transcription and then synthesized by sangon biotech co. ( japan ) . pcr were performed using syber green real - time pcr regent box ( toyobo ) in a total volume of 20  l . pcr conditions for foxp3 was 95c for 1  min , 40 cycles of 95c for 15  s , 61c for 15  s , 72c for 45  s , but the annealing temperature of rort was 64c . samples were analyzed utilizing the abi prism 7900 sequence detection system ( applied biosystems , foster city , ca , usa ) . glyceraldehyde-3-phosphate dehydrogenase ( gapdh ) was used as a housekeeping gene for normalization , and a no template sample was used as a negative control . the plasma levels of il-17 , il-6 , tgf-1 , and il-10 were measured by enzyme - linked immunosorbent assay ( elisa ) , following the manufacture 's instructions ( elisa kits , all from r&d system ) . the minimal detectable concentrations were 2  pg / ml for il-17 , 0.7  pg / ml for il-6 , 5  pg / ml for tgf-1 and 7.8  pg / ml for il-10 . as previously described , serum levels of highly sensitive crp ( hscrp ) were measured with a particle - enhanced immunoturbidimetry ( beijing o&d biotech company ltd , cox bio china , beijing , china ) . values are expressed as mean  standard deviation ( sd ) in the tables and figures . grouped data were analysed using a one - way analysis of variance ( anova ) followed by the student - newman - keuls test . when the equal variance test failed , a mann - whitney rank sum test was used . spearman 's correlation was used as a test of correlation between two continuous variables . a p value of < 0.05 indicates significance . statistical analysis was performed using a commercial software package ( spss , version 15 ; spss ; chicago , il ) . thus , a total of twenty - three patients were enrolled as mild to moderate osas group and 21 patients were screened as severe osas group . the mean ahi in osas group was 40.41  20.68 and mean age of osas patients was 46.43  18.22 years . as shown , ees score and psg parameters were significantly higher in the osas group comparing with the control group ( p < 0.05 ) . however , no statistically significant differences were found between three groups from the standpoint of age and bmi ( p > 0.05 ) . as shown in figure 1(a ) , the prevalence of th17 cells in pbmcs was expressed as a ratio of cd4il17 t cells / cd4 t cells . the frequence of th17 was evidently increased in the peripheral blood of osas patients ( 3.08  0.68% ) than those in normal controls ( 1.65  0.49% ; p < 0.001 ) . furthermore , the percentage of th17 was markedly higher in patients with severe osas ( 3.42  0.49% ) than those in subgroup with mild to moderate osas ( 2.77  0.68% ; p = 0.002 ) . as shown in table 2 and figure 1(b ) , the frequency of treg was significantly decreased in the peripheral blood of osas patients ( 1.50  0.38% ) compared to control group ( 2.81  0.46% ; p < 0.001 ) . moreover , significant difference was found between severe osas group and patients with mild to moderate osas ( 1.30  0.31% versus 1.69  0.34% , p = 0.001 ) . nevertheless , the percentage of cd4cd25 t lymphocytes was similar in the three groups ( data not shown ) . when the balance of th17 and treg was further investigated , their relationship was expressed as a ratio of th17/treg . we demonstrated that the ratio of th17/treg was highest in patients with severe osas ( 2.80  0.84 ) , lower in those patients with mild to moderate osas ( 1.71  0.67 ) and lowest in control subjects ( 0.58  0.13 ) ( figure 1(c ) ) . as a result , the th17/treg ratio was significantly increased in osa patients comparing with control group ( 2.23  0.94 versus 0.58  0.13 , p < 0.001 ) . rort is an important transcription factor for the differentiation of th17 , while foxp3 is the master transcription factor in treg . we thus analyzed the levels of transcription factors for th17 ( rort ) and treg ( foxp3 ) by rt - qpcr in pbmcs from included subjects . as shown in figure 2 , the levels of rort expression were much upregulated in the osas group ( 3.18  1.19 ) than those in the health control group ( 1.42  0.32 , p < 0.01 ) . and there was significant difference between the severe ( 4.25  0.79 ) and mild to moderate subgroups ( 2.21  0.37 ) within osas patients ( p < 0.05 ) . in contrast , the expression of foxp3 was markedly lower in the osas patients ( 2.50  1.38 ) as compared with the control group ( 4.10  0.97 , p < 0.01 ) , while foxp3 levels in severe osas group ( 1.33  0.35 ) were significantly downregulated than that of the subgroup with mild to moderate osas ( 3.56  1.07 , p < 0.01 ) . plasma levels of il-17 , il-6 , tgf-1 , il-10 , and hscrp were detected in normal controls and osas patients by means of elisa tests ( table 2 , figure 3 ) . il-17 in severe patients ( 75.24  11.40  pg / ml ) and mild to moderate apnea ( 65.78  13.97 pg / ml ) were both significantly higher compared with concentration in control group ( 55.12  18.23 the level of il-6 in osas patients ( 55.09  17.02  pg / ml ) was significant higher that in control group ( 42.56  21.15  pg / ml , p < 0.01 ) , however it 's comparable in severe subgroup and patients with mild to moderate osas ( p > 0.05 ) . as shown in figure 3 , while plasma tgf-1 in severe patients ( 52.19  12.53  pg / ml ) and mild to moderate patients ( 74.26  11.40  pg / ml ) with osas were markedly lower than those in the control group ( 146.81  21.36  pg / ml ; p < 0.01 ) . in contrast , the same differences were not found for il-10 ( p > 0.05 ) . pg / ml ) compared with those in control group ( 60.33  20.38  pg / ml ; p < 0.01 ) . moreover , hscrp was markedly higher in subjects with severe osas ( 253.71  36.49 pg / ml ) when compared to subjects with mild to moderate osas ( 118.65  16.72  pg / ml ; p < 0.01 ) . in 44 patients with osas , the plasma concentration of il-17 was positively correlated with peripheral blood frequencies of th17 ( r = 0.525 , p = 0.000 ) ( figure 4(a ) ) . there were significantly positive correlations between th17 frequencies and the level of rort  mrna in pbmc from osa patients ( r = 0.483 , p = 0.001 ) ( table 3 , figure 4(b ) ) . and tgf-1 concentration was positively correlated with peripheral blood frequencies of treg ( r = 0.427 , p = 0.004 ) in osas patients ( figure 4(d ) ) . significantly positive correlations were found between peripheral treg percentage and the expression of foxp3  mrna in pmbcs from osas patients ( r = 0.435 , p = 0.003 ) ( figure 4(c ) ) . we next sought to analyze the correction of the ratio of treg to th17 cells to the disease severity in osas patients ( table 3 ) . the plasma level of hscrp has been proved to have a close relationship with severity and complication in osas patients . in current osas patients , serum level of hscrp in contrast , serum level of hscrp was positively related with th17 frequence ( r = 0.372 , p = 0.013 ) and negatively related with treg frequence ( r = 0.433 , p = 0.003 ) . and also , hscrp level was positively correlated with the ratio of th17/treg ( r = 0.475 , p = 0.001 ) in osas patients . as shown in table 3 , ahi index was positively correlated with circulating th17/treg ratio ( r = 0.321 , p = 0.029 ) , but not with single percentage of th17 or treg in pbmc from osas patients ( p > 0.05 ) . this result suggests that decreased ratio of treg to th17 cells may be an indicator for the disease severity of osas indicated by ahi . there was no significant correlation between the other psg parameters and the ratio of th17 to treg in the osas patients ( p > 0.05 ) . the relationship between bmi or ess scores and th17/treg ratios in osas patients was also studied , but no correlations were identified ( p > 0.05 ) . the present data provide direct evidence that osas patients exhibited a significant increase in peripheral th17 frequency , th17-related cytokines ( il-17 ) and transcription factor ( rort ) levels , and dramatic decrease in treg frequency , treg - related cytokines ( tgf-1 ) and transcription factor ( foxp3 ) levels when compared to the control group . it 's the first clue that circulating treg / th17 balance is impaired in these patients . more important , circulating treg / th17 ratio negatively correlated with the plasmatic hscrp level and severity of osas , as determined by ahi . these results suggest a potential role for a higher ratio of circulating th17/treg , which indicates the systemic inflammation in the pathogenesis of osas and subsequent complications . to the best of our knowledge , this is the first study to examine the circulating th17 and treg cells and their balance in osas patients . bollinger et al . demonstrated that cd4cd25 natural regulatory t cells ( ntreg ) number and function follow a rhythm across the 24-h period and sleep deprivation severely disturbs the functional rhythm of ntreg cells . in agreement , we found that the frequencies of treg cells and the expression of foxp3 were significantly lower in patients with osas when compared to normal persons . by far , there is no research investigating the role of peripheral frequence of th17 cells in any sleep disorders . in this study , we found that patients with osas exhibited a significant increase in peripheral th17 number , th17-related cytokines ( il-17 ) and rort levels when compared to normal persons . as a result , a treg / th17 functional imbalance exists in osas patients , suggesting a potential role for treg / th17 imbalance in the pathogenesis of osas . th17 cells and treg cells not only share the same origin but also are mutually antagonistic in function . th17 cells have been established as an important t - helper effectors lineage , which mediates protection against extracellular pathogens . on the negative side , th17 cells also appear to be the driving force in the pathogenesis of autoimmune and inflammatory disorders . in contrast to th17 cells , cd4cd25 and foxp3 ( tregs ) play a critical role in maintaining self - tolerance and in preventing organ - specific autoimmunity , allergy , and allograft rejection . t cell development exhibits a degree of plasticity that meets local requirements and thereby transgresses lineage barriers . although these two t cell subsets have a reciprocal relationship and differentiation pathways , it was recently reported that tregs are able to differentiate into il-17-producing cells , and that human peripheral blood and lymphoid tissue contain a significant number of cd4foxp3 t cells that have the capacity to produce il-17 upon activation . especially , for the first time , we report that the ratio of th17/treg cells , but not peripheral th17 or treg frequence alone , had a linear negative correlation with osas severity indicated by ahi . in accordance to our results , freire et al . found no association of ahi with total lymphocyte , neutrophil , or peripheral blood cell count alterations . recently , many investigators raised the notion of a th17/treg balance and reported an imbalance in patients with various autoimmune and inflammatory diseases [ 1417 ] . a higher th17/treg ratio may characterize a more severity in autoimmune , inflammatory and allergic diseases . it illustrates that the balance or interplay between various types of immune cells may be the better predictors for clinical outcome of patients . the ratio of treg / th17 may reflect a specific skewed balance of anti- and proinflammatory t cell subsets in osas patients , while absolute numbers reflect the general activation . because of the reciprocal developmental pathway for the generation and the opposite effects of th17 and treg cells , treg / th17 subsets may therefore have been evolved to regulate systematic inflammation , analogous to the dichotomy of th1/th2 t - cell subsets . as a result , the th17/treg ratio became an important tool in describing and understanding various immunological conditions , such as tumor , inflammatory , autoimmune , and allergic disease or models . adenoid hypertrophy is the most common cause of upper airway obstruction and sleep - disordered breathing in children . sade et al . evaluated the adenoidal lymphocyte subsets to describe the percentage of various lymphocyte subsets in hypertrophied adenoids of children and correlated them with symptom severity . they found a significant negative linear correlation between the th17/treg ratio and the patients ' clinical scores independent of age and gender . however , the pathogenesis and pathophysiology of osas in adult and children were not completely identical . moreover , it may reflect the inconsistence between local and systemic inflammation in osas . in the context of acute and chronic infectious existing in local adenoids of children , a lower th17/treg ratio might decrease the total clearance of microorganisms and increase chronic immune activation and proliferation of lymphocytes , thereby causing hypertrophy of lymph nodes , including adenoids and tonsils . it has recently been hypothesized that adult osas might be a triggering factor for the development of autoimmune phenomena . under the circumstances , a higher th17/treg ratio may bring on the loss of tolerance and regulation , and finally a persistent , low - degree systemic inflammatory reaction characterized by autoimmune or allergic diseases . activation of t lymphocytes is among the crucial steps leading to the release of inflammatory mediators and adhesion molecules . activation of inflammatory cells and their interaction with endothelial cells have been demonstrated in osas . in a series of experiments , dyugovskaya et al . showed that various subpopulations of cytotoxic t cells of patients with osas acquire an activated phenotype with the downstream consequence of increased cytotoxicity against endothelial cells [ 10 , 11 ] . the research in the past five years have demonstrated that subsets of t lymphocytes , both effector t cells such as th1 and th2 lymphocytes , as well as th17 and treg , play critical roles in the development of atherogenesis and vascular remodeling [ 27 , 28 ] . several large - scale prospective studies have shown that the hscrp level is an independent predictor of risk of myocardial infarction , stroke , peripheral vascular disease , and vascular death , making it a useful marker for cardiovascular risk stratification . previous works have demonstrated an independent relationship between osas and an elevated hscrp [ 30 , 31 ] . a close link between circulating treg / th17 kim et al . recently reported that foxp3  dna methylation levels positively correlated with hscrp levels and ahi in 47 osas children . a high foxp3  dna methylation may favor the downregulation of foxp3 protein expression and thus reduce the number of tregs , thereby favoring increased systemic inflammatory responses in pediatric osas . accordingly , their results corroborated our observation that the ratio of treg / th17 was negatively correlated with hscrp and ahi in osas patients . it should be careful in understanding and comparing previous results because only sensitive measurement of hscrp was valid to demonstrate an association with ahi . the cytokine milieu of the local environment plays a pivotal role in the differentiation from naive cd4 t cells to treg or th17 cells . in the present study , results showed that the concentrations of il-6 and il-17 , both of which promote the differentiation of th17 cells , were all significantly higher in osas patients , and il-17 concentrations were positively correlated with th17 cells frequencies . these suggested that the proinflammatory cytokine microenvironment , characterized by elevated il-6 and il-17 levels and decreased tgf-1 concentrations , could potentially support the continued generation of th17 cells but meanwhile suppress the development of treg cells , which led to the th17/treg numerical imbalance in osas patients [ 33 , 34 ] . this numerical imbalance might consequently result in the functional imbalance of th17/treg which contributed to enhancing the formation of the inflammatory cytokine microenvironment , and eventually formed a positive feedback mechanism to amplify proinflammatory immune responses . a potential reason for the immune system activation in osas patients may be the obesity that represents a major risk factor and usually accompanies osas . although the bmi levels remained comparable , there were clearly some overweight men with a mean bmi around 28  kg / m were included in our cohort . further research concerning this issue may enroll only non - overweight osas groups for analysis . and other measurements , such as hip - waist ratio or densitometry of abdominal fat , can replace bmi to assess obesity in osas patients . our data offered direct evidence for the skewed balance of th17/treg , pro- and anti - inflammatory t cell subsets in osas patients . we also identified that the ratio of th17/treg does not only correlate with inflammatory marker but is also associated with disease severity of osas . thus , our results suggest that increased ratios of th17/treg subpopulations may play a role in the pathogenesis of osas . these results opened an alternative explanation for the substantial activation of immune cells as well as the development of osas and complications , which may have significant impacts on the prevention and treatment of osas patients . the biological significance and clinical implications of the imbalance of serum th17/treg merit future confirmatory and mechanistic studies in larger cohorts . the further studies may be designed to observe the change of treg / th17 imbalance in osas during constant positive airway pressure ( cpap ) treatment and to investigate the impact of comorbidies on the treg / th17 balance in osas patients . restoration of the immune imbalance may be a future therapeutic approach for inhibiting systemic inflammatory processes in order to ameliorate the cardiovascular risk factors associated with osas .
obstructive sleep apnoea syndrome ( osas ) is a chronic inflammatory disease regulated by t lymphocytes . 
 our purpose is to assess the pattern of th17 cells and cd4+cd25+foxp3 + regulatory t ( treg ) cells in peripheral blood of patients with osas . 
 fourty - four osas men and 20 healthy volunteers were enrolled . 
 twenty - three patients were classified into mild to moderate group and 21 cases were classified into severe group according to the severity of osas . 
 we detected the frequencies of th17 and treg and related serum cytokines secretion and expressions of key transcription factors . 
 osas patients revealed significant increase in peripheral th17 number , th17-related cytokines ( il-17 and il-6 ) , and rort mrna levels . 
 they also presented a significant decrease in treg number , treg - related cytokines ( tgf-1 ) , and foxp3 mrna levels as compared with normal persons . as a result , 
 the th17/treg ratios were markedly more upregulated in osas patients than those in control group . 
 furthermore , the th17/treg ratio was positively related to the severity of osas and serum levels of c - reactive protein . 
 the development of osas may be associated with peripheral th17/treg imbalance and characterized by a proinflammatory cytokine microenvironment . 
 these results opened an alternative explanation for the substantial activation of immune cells in osas and the development of related complications .