Peripheral Blood Regulatory T Cells and IL-6 are Associated with Cognitive Impairment After Acute Ischemic Stroke

Introduction

Acute ischemic stroke (AIS) is a cerebrovascular condition that accounts for high rates of disability and death. About one-third of stroke patients experience cognitive decline or post-stroke cognitive impairment (PSCI) and post-stroke dementia (PSD), creating substantial family burdens.¹ AIS activates microglia and inflammatory factors, initiating neuroinflammatory responses, and increases the permeability of the blood-brain barrier (BBB), promoting PSCI progression.²

Tregs have been suggested as early biomarkers of cognitive impairment and may be involved in the dysregulation responsible. The adoptive transfer of Tregs improved cognitive deficits in animal models of Alzheimer’s disease (AD), indicating the potential for Treg cell therapy.³ T cell receptor (TCR)-engineered Tregs decreased amyloid-beta (Aβ) accumulation in brain tissue and enhanced behavioral outcomes in the APP/PS1 AD mouse model, illustrating that TCR Aβ-specific Tregs may improve cognitive function. TCR Aβ-Tregs may regulate Aβ levels and neuroinflammation by modulating the immune environment, reversing neurotoxicity and enhancing cognition.⁴ Studies in AD patients have shown reduced neuroinflammation and improved cognitive abilities after transplant of Tregs functionally enhanced by in vitro expansion.⁵ Research on roles of Tregs in post-stroke cognitive impairment remains limited, although an imbalance of Th17 and Treg cells has been suggested to exacerbate cognitive decline.⁶ Tregs may function as memory cells identified by brain cells, reducing neuroinflammation, supporting repair of white matter and accelerating post-stroke neurological recovery.⁷

IL-6 is a pro-inflammatory cytokine involved in the progression of cognitive decline. It causes chronic neuroinflammatory responses within the central nervous system by an effect on the permeability of the blood-brain barrier (BBB), which impairs neuronal function and promotes the deterioration of cognitive abilities.⁸ Elevated serum IL-6 has been linked to cognitive decline and reduced executive function in older adults, substantiating the role of neuroinflammation. Indeed, IL-6 and the pro-inflammatory tumor necrosis factor-alpha (TNF-α) have both been implicated in the pathological inflammation linked to cognitive impairment.⁹ Patients with IL-6 levels in the highest quartile of a 1003 patient cohort with AIS and transient ischemic attack (TIA) had a greater risk of cognitive decline compared with those in the lowest quartile (25.90%vs16.80%).¹⁰ Patients experiencing cognitive impairment after stroke are generally considered to have increased IL-6, which may be a predictive marker for this dysfunction.¹¹

Neuroinflammation is acknowledged to be involved in PSCI development, although mechanisms remain unclear. The causes of PSCI require urgent clarification to enable targeted intervention strategies. Tregs and IL-6 play crucial roles in modulating inflammation after stroke. Recent studies have shown that amphiregulin (AREG) regulates the IL-6 and STAT3 signaling pathway in microglia and astrocytes, which is a critical aspect of the neuroprotective function of brain Tregs.¹² Additionally, excessive IL-6 production inhibits Foxp3 expression and Tregs development.¹³ However, Nevertheless, it is still unclear whether Tregs’ effects related to IL-6 contribute to PSCI, and if so, through which mechanisms. The relationship between peripheral blood Tregs, IL-6 and cognitive impairment in AIS patients was investigated during the current work to allow evaluation of Treg percentage and IL-6 as biomarkers of PSCI to explore its underlying mechanism. The aim was to contribute to immunotherapeutic approaches for PSCI.

Materials and Methods

Study Design and Subjects

A cohort of 256 patients, diagnosed with AIS and admitted to the Department of Neurology at the First Affiliated Hospital of Anhui University of Science and Technology (Huainan First People’s Hospital) between January 2023 and October 2024, were enrolled in the current retrospective and single-center study. Patients with acute cerebral infarction underwent neuropsychological evaluations using the Montreal Cognitive Assessment (MoCA) and Clinical Dementia Rating (CDR) scales and clinical examination within one week of stroke onset. The blood sample was collected within 24 hours of admission. Follow-up assessments using the same scales were conducted six months post-stroke. Patients were classified into four groups of post-stroke no cognitive impairment (PSNCI; n=129), post-stroke cognitive impairment (PSCI; n=108), post-stroke cognitive impairment with no dementia (PSCIN; n=87) and post-stroke dementia (PSD; n=21).

Inclusion Criteria:

1. Diagnosis of AIS confirmed by diffusion-weighted imaging (DWI) within 72 hours of symptom onset;
2. Written informed consent obtained:
3. Aged between 40 and 88 years;
4. Ability to independently participate in all neuropsychological assessments;
5. Pre-stroke modified Rankin Scale (mRS) score of 2 or less.

Exclusion Criteria:

1. Presence of cognitive impairment prior to stroke onset;
2. Cognitive dysfunction attributable to other neurological or systemic conditions associated with cognitive decline, including Parkinson’s disease, multiple system atrophy, metabolic disorders, non-vascular white matter disease, neurosyphilis and psychiatric illnesses;
3. Systemic illnesses, such as malignancies, hematologic disorders or autoimmune diseases;
4. Inability to cooperate with neuropsychological assessments;
5. History of severe stroke-related sequelae;
6. Severe cardiac, hepatic or renal dysfunction or metabolic diseases within the preceding three months;
7. Refusal to provide informed consent or unwillingness to comply with study procedures and follow-up assessments.

Evaluation of Cognitive Impairment

Two to three neurologists with expertise in cognitive assessment scales conducted face-to-face evaluations of all eligible AIS patients using the MoCA and CDR scales. Assessments were made in a quiet environment and scheduled at times when patients were deemed to be in an optimal state to complete the evaluations. The same cognitive assessments were repeated six months after patient discharge. Patients with a MoCA score < 22 were classified as having PSCI.¹⁴ Patients with CDR scores between 0.5 and 1 were categorized as having PSCIND¹⁵ and those with scores between 2 to 3 as having PSD.

Imaging Assessment

All participants underwent detailed cranial magnetic resonance imaging (MRI) using either 1.5T or 3.0T scanners (made in the United States). The imaging protocol included T1-weighted, T2-weighted, diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences, complemented by vascular imaging of the head and neck.

White Matter Hyperintensities (WMH)

WMH¹⁶ were evaluated by modified Fazekas grading scale (range: 0 to 6 points) applied to T2-weighted or FLAIR MRI scans with separate assessment of periventricular and deep WMH. Lesions involving deep gray WMH were classified as subcortical hyperintensities to align with the broader definition of subcortical regions, similar to recent subcortical small infarcts. Individual scores from the two regions were aggregated to yield a total score which was categorized into three grades of mild (0–2 points), moderate (3–4 points) or severe (5–6 points).

Vital Brain Infarction (VBI)

Infarctions located in the left thalamus, left frontotemporal lobe and right parietal lobe were designated as vital brain infarction (VBI)¹⁷ from DWI findings.

Infarct volume in AIS patients was quantified using the Pullicito¹⁸ formula and dichotomized into volumes ≥5 cm³ or <5 cm³.

Stroke subtypes were categorized according to TOAST classification, including large artery atherosclerosis (LAA), cardioembolic infarction (CE), small artery occlusion (SAO), stroke of other determined etiology (SOE) and stroke of undetermined etiology (SUE). SOE and SUE were combined into a single category of other types (OT) in the current analysis. AIS was classified according to the Oxfordshire Community Stroke Project (OCSP) criteria into total anterior circulation infarction (TACI), partial anterior circulation infarction (PACI), posterior circulation infarction (POCI) and lacunar infarction (LACI).

Brain atrophy was assessed by Global Cortical Atrophy (GCA) scale (range: grade 0–3),¹⁹ reflecting the severity of cortical atrophy across the entire brain. Two grades of brain atrophy were considered: mild (0–1 points) or moderate to severe (2–3 points).

Measurement of Peripheral Blood Tregs and IL-6

Mouse anti-human monoclonal antibodies targeting CD4-PC, CD3-PC, CD8-PC, CD45-PC and CD25-PE-CY7C were purchased from Beckman Coulter and used to analyze samples of 2mL peripheral whole blood anticoagulated with EDTA, at room temperature and usually processed within 24 hours. Samples that were processed after 24 hours were stored at 4–8°C.

During the sample preparation, a clean test tube was used to which 100 µL of whole blood specimen was added. Subsequently, fluorescently labeled monoclonal antibodies (CD4-PE, CD127-PE-CY5, CD25-PE-CY7) were introduced. The mixture was gently vortexed and incubated at room temperature in the dark for 15 minutes. 300 µL of BC OptiLyse C lysing solution was added to mix thoroughly by vortexing in the dark for 5 minutes. The sample was then centrifuged at 1700 rpm, the supernatant discarded, and the pellet washed with 2 mL of PBS by centrifugation at 1700 rpm. After discarding the supernatant, 600 µL of PBS was added to resuspend the cells, and the sample was mixed thoroughly prior to analysis. Tregs were detected by flow cytometry (Beckman Coulter, USA) and data acquired by Beckman CXP software and analyzed by Beckman Kaluza software to quantify proportions of CD4+CD25++CD127low regulatory T cells within the total CD4+ lymphocyte population (expressed as Tregs%). IL-6 was quantified by enzyme-linked immunosorbent assay (ELISA) kit (Siemens, UK).

Statistical Analysis

Data were processed using SPSS version 26.0, and graphical presentations were created using GraphPad Prism 9.5.0. Variable normality and homogeneity of variance were assessed. Continuous variables with normal distribution are reported as mean ± standard deviation and intergroup comparisons were conducted by one-way analysis of variance (ANOVA). Categorical variables are presented as frequencies and percentages [n (%)] with intergroup differences evaluated by chi-square test. Non-normally distributed continuous variables are expressed as median (first quartile, third quartile) [M (Q1, Q3)] and intergroup comparisons were performed by Mann–Whitney U-test. Univariate analyses followed by binary logistic regression were utilized to identify risk factors associated with the development of cognitive impairment after AIS. Diagnostic accuracy for post-stroke cognitive impairment was assessed by receiver operating characteristic (ROC) curve analysis. Statistical significance was defined as a p-value < 0.05.

Results

256 AIS patients were initially enrolled, 19 of whom were lost during the six-month follow-up, leaving 237 patients with complete clinical data and successful follow-up. These patients were categorized into 108 PSCI patients and 129 PSNCI patients. The first group was subdivided into 87 patients with PSCIND and 21 patients with PSD. Baseline clinical characteristics, including demographic variables, cerebrovascular risk factors and hematological parameters, are summarized in Table 1. Statistically significant differences were found between PSNCI and PSCI patients in age (p = 0.048), uric acid (UA) levels (p = 0.031), presence of diabetes and admission NIHSS scores (p < 0.001). Significant PSNCI vs. PSCIND differences were also found in the prevalence of coronary heart disease (p = 0.027) and admission NIHSS scores (p < 0.001) and PSNCI vs. PSD differences in age (p = 0.017), diabetes status (p = 0.031) and admission NIHSS scores (p < 0.001, Table 1).

Table 1 Clinical and Demographic Patient Characteristics

Comparative analysis of imaging findings between PSNCI and PSCI patients demonstrated significant differences in VBI (p < 0.001) and WMH (p = 0.010) but no significant differences in infarct volume (p=0.115), TOAST (p=0.874) or brain atrophy (p=0.789). Significant PSNCI vs. PSCIND differences were identified in VBI (p<0.001) and WMH (p = 0.027) and significant PSNCI vs. PSD differences in VBI (p < 0.001), WMH (p = 0.025) and brain atrophy (p = 0.003, Table 2). Tregs% was elevated in PSCI (2.35±0.87), PSCIND (2.04±0.79) and PSD (2.54±0.95) relative to PSNCI (2.00±0.83) and significant differences were observed between the PSNCI and PSCI groups (p = 0.014) and between PSNCI and PSD (p = 0.007). IL-6 concentrations were also elevated in PSCI, PSCIND and PSD patients relative to PSNCI with significant differences in PSNCI vs. PSCI (p = 0.030) and PSNCI vs. PSD (p < 0.001).

Table 2 Clinical Imaging Characteristics [n (%)]

Binary logistic regression analysis was conducted to evaluate the association between Tregs% and PSCI. After adjustment for confounding risk factors, Tregs% (OR=1.122; 95% CI: 1.006–1.251; p=0.038) was found to be an independent risk factor for PSCI (Table 3). The AUC values for IL-6 and Tregs% in predicting cognitive impairment in PSCI patients were 0.660 and 0.718, respectively, and, when the two risk factors were combined, the AUC was 0.763 with a sensitivity of 87.0% and specificity of 67.1% (Table 4 and Figure 1).

Table 3 Logistic Regression Analysis of Tregs and IL-6 in Cognitive Impairment After AIS

Table 4 Evaluation of the Efficacy of Tregs% and IL-6 in Predicting Cognitive Impairment After AIS

Figure 1 ROC curve of Tregs% and IL-6 in cognitive impairment after AIS. Predictive values for PSCI,Area under the curve 0.763 for Tregs% and IL-6. Abbreviations: AIS, acute ischemic stroke; PSCI, post-stroke cognitive impairment; Tregs, Regulatory T cells; IL-6, interleukin-6.

Binary logistic regression identified IL-6 (OR=1.269; 95% CI: 1.079–1.492; p=0.004) as a significant predictor of PSD and this relationship remained after adjustment for confounding risk factors (OR=1.307; 95% CI: 1.058–1.614; p=0.013, Table 5). ROC curve analysis demonstrated an AUC of 0.805 (95% CI: 0.681–0.929; p<0.01) and the optimal cutoff value for IL-6 was 12.40pg/mL, corresponding to a sensitivity of 84% and specificity of 78% (Figure 2). Multivariate logistic regression analysis demonstrated relationship between Tregs%, IL-6 and the severity of PSCI, Tregs% (P=0.006) IL-6 (P=0.001) were associated with the PSD Group after adjusting for potential confounding factors, unassociated with the PSNCI group (Table 6).

Table 5 Logistic Regression Analysis of Tregs% and IL-6 in Dementia in AIS

Table 6 Logistic Regression Analysis of Tregs% and IL-6 Across Different Degrees of PSCI

Figure 2 ROC curve for predicting PSD using IL-6. Predictive values for PSD, Area under the curve 0.805 for IL-6. Abbreviations: PSD, post-stroke dementias; IL-6, interleukin-6.

A subgroup analysis was performed to investigate the Association between age, vascular risk factors, Tregs%, and IL-6. In This study, none of the subgroups, including age, sex, the presence of hypertension or diabetes or Coronary heart disease or Stroke, as well as smoking and Alcohol consumption, significantly modified the association between Tregs%, IL-6, and PSCI (all P values for interaction > 0.05, Figure 3).

Figure 3 Subgroup analyses of the association between Tregs%, IL-6 level and post-stroke cognitive. In the multivariate models, confounding factors, such as age, sex, Diabetes, Coronary heart disease, Stroke, Hypertension, Smoking, Alcohol consumption, UA, NIHSS, VBI and WMH were included unless the variables were used as a subgroup study. Abbreviations: Tregs, Regulatory T cells; IL-6, interleukin-6; OR, odds ratio; CI, confidence intervals; VBI, vital brain infarction; WMH, White matter hyperintensities; UA, Uric Acid.

Discussion

Tregs% and IL-6 were found to be elevated in the peripheral blood of the present cohort of PSCI patients with increases being particularly pronounced in PSD. Tregs% was identified as an independent risk factor for PSCI and the combination of Tregs% and IL-6 showed enhanced predictive accuracy for PSCI. IL-6 was also found to be an independent risk factor for PSD and may be a biomarker for PSD prediction.

The involvement of Tregs in the pathophysiology of AIS is acknowledged to be significant, but a complex dual nature is shown, where the impact may be either protective or may exacerbate stroke-related injury. Empirical evidence suggests Tregs numbers to fluctuate during different AIS stages, with low numbers in the initial stages and elevated levels beyond one month post-stroke. Temporal variations influence stroke outcomes and neurological recovery trajectories.^20–22 Tregs contribute to BBB preservation in the acute phase by mitigating inflammatory responses, but excessive numbers during later stages may impair BBB function, impeding neurological recuperation.²³ Early post-stroke increases in Tregs populations have sometimes been reported, but chronic inflammatory conditions may induce Tregs dysfunction or exhaustion, diminishing the protective effect and facilitating the development and progression of cognitive impairment.^24–26 Indeed,Tregs secrete anti-inflammatory cytokines, such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β),²⁷ which inhibit microglial polarization toward the pro-inflammatory M1 phenotype while promoting the anti-inflammatory M2 phenotype, attenuating neuroinflammation-associated cognitive deficits.^28,29 Tregs have also been shown to suppress activation of the NLRP3 inflammasome and reduce the secretion pro-inflammatory cytokines, including IL-1β and IL-6, alleviating inflammatory burden within cerebral tissue and mitigating neuronal death and synaptic dysfunction.^30,31 Tregs facilitate tissue repair and stimulate immune tolerance by modulating the activity of microglia and macrophages, mitigating white matter injury. The depletion of endogenous Tregs has been shown to delay functional recovery after stroke and to exacerbate white matter damage.^32,33 This observation implies that the augmentation of Tregs populations may enhance white matter integrity.³⁴ In our study, Elevated Tregs percentages in the early post-stroke stages were shown to be a risk factor for cognitive impairment after AIS, with an AUC value of 0.718 (95% CI: 0.600–0.836), and Tregs levels may be a valuable biomarker for early prediction and evaluation of PSCI risk, enabling timely therapeutic intervention. In fact, emerging evidence suggests that the consistent expression of FoxP3 does not fully explain the functional stability of Tregs. This is attributed to the considerable phenotypic and functional heterogeneity observed, which has prompted the classification of distinct Tregs subsets. Among them, there is a group of Tregs called “fragile Tregs”, which are characterized by the expression of FoxP3 and inflammatory cytokines but no immunosuppressive functions. This fragile subset of Tregs may directly contribute to the initiation of cytokine storms and exacerbate disease severity by promoting proinflammatory responses^35,36 While the potent immunosuppressive properties of Tregs serve to mitigate detrimental inflammatory responses, excessive immunosuppression can induce systemic immune compromise, thereby increasing patients’ vulnerability to infectious complications. Helios-positive regulatory T cells (H+Tregs) had favor of pro-inflammatory than Helios-negative regulatory T cells (H-Tregs) in the early day after stroke. Notably, H+Tregs on day 3 may contribute to an elevated risk of infection due to their strong immunosuppressive properties.³⁷ Therefor, The function of Tregs depends not on their quantity, but on their heterogeneity, functionality, and different subtypes. Our findings indicate that elevated Tregs are correlated with PSCI, which may contradict previous findings. It is evident that fragile Tregs could promote severe inflammation and impair the immunosuppressive function of Treg cells in acute and chronic inflammation. Current studies have shown that patients with severe COVID-19 have an increased proportion of Treg cells (CD3+CD4+CD25+FoxP3+), which is associated with a worse prognosis compared to those with mild COVID-19.³⁸ Similarly, it has been reported that Tregs fragility may significantly contribute to the pathogenesis and progression of moyamoya disease (MMD) under chronic inflammation. Notably, in MMD, Tregs showed a marked increase, specifically in the proportions of unstable and fragile Tregs, accompanied by a reduction in the proportion of stable Tregs.³⁹ One potential explanation for this discrepancy is that the proportion of Tregs measured may not accurately reflect their functional capacity in PSCI. It is plausible that during the acute phase of AIS, the heightened inflammatory response leads to elevated Tregs levels but gradually becoming more fragile Tregs that promote the development of PSCI. An initial elevation in the population of Tregs could promote a pro-inflammatory effect and may contribute to the development of PSCI. Significant challenges remain that require further investigation regarding the complexity and stability of Tregs function.

IL-6 is a pleiotropic inflammatory cytokine with both pro- and anti-inflammatory properties. Excessive IL-6 expression activates neurocircuits that contribute to neuronal injury and precipitate PSCI,⁴⁰ and elevated IL-6 has been positively correlated with the severity of cognitive deficits following stroke. A multicenter study involving 7053 patients with ischemic stroke and transient ischemic attack (TIA) demonstrated the association of early elevated IL-6 levels with increased stroke severity, higher recurrence rates and greater disability.⁴¹ IL-6 increases during the acute post-stroke phase as a consequence of ischemic brain injury, triggering an inflammatory response. Empirical evidence indicates that elevated IL-6 compromises BBB integrity, allowing the infiltration of immune cells and neurotoxic substances into brain parenchyma.⁴² Cerebrospinal fluid (CSF) and serum IL-6 are thus considered potential biomarkers for post-stroke cognitive decline.⁴³ Longitudinal studies have identified significant associations between IL-6 concentrations at 3 and 6 months post-stroke and cognitive performance, assessed by instruments such as the MoCA and the Mini-Mental State Examination (MMSE),^41,44 and cytokine profiling has correlated increased IL-6, IL-1β, IL-8, IL-10 and IL-12 with poorer cognitive outcomes. For instance, a study of 455 ischemic stroke patients reported a relationship between IL-6 levels and MoCA scores at 18 months post-event.⁴⁵ Investigations into inflammatory markers have also identified associations between erythrocyte sedimentation rate, serum and CSF concentrations of C-reactive protein (CRP), IL-6, IL-10 and IL-12 and the incidence of PSCI. Stroke survivors with cognitive impairment also present with higher IL-6 levels than those in whom cognitive function is preserved, substantiating IL-6 as a prognostic indicator for PSCI. IL-6 expression was found to be elevated in the early phase of AIS in the current cohort of patients who later developed cognitive impairment, particularly those with PSD in this study. Indeed, IL-6 was a risk factor for PSD with an AUC value of 0.805 (95% CI: 0.681–0.929, p < 0.01). The optimal cutoff value was 12.40pg/mL, corresponding to a sensitivity of 84% and specificity of 78%. IL-6 (P=0.001) and Tregs% (P=0.006) are significantly associated with severe PSCI, especially in PSD. These findings suggest that early elevated IL-6 expression may be a valuable prognostic tool for assessing the risk of post-stroke cognitive decline. IL-6 is also a potential target for therapeutic intervention aimed at mitigating cognitive sequelae of stroke. IL-6 combined with Tregs provides a more effective prediction of PSCI than individual prediction. IL-6 plays a critical role in the differentiation, functionality, and stability of Tregs. Elevated levels of IL-6 were frequently observed in various autoimmune disorders and malignancies, where it contributes to disease progression by promoting Th17 differentiation and inhibiting Tregs function.⁴⁶ Notably, IL-6 receptor (IL-6R) signaling within Tregs is essential for maintaining epithelial homeostasis and orchestrating protective inflammatory responses in inflammatory bowel disease (IBD).⁴⁷ IL-6 signaling pathway is critically involved in the functions of Tregs. IL-6 in vitro plays a vital role in the balance between Th17 cells and Foxp3+Tregs because of IL-6 inhabiting the TGF-β induced generation of Foxp3+ Tregs and driving Th17 cell.⁴⁸ It has been demonstrated that elevated levels of IL-6 negate the suppressive function of thymus-derived Tregs (nTregs). Meanwhile, it has been shown that these nTregs lost Foxp3 expression as well as their suppressive capacity in the simulation of increased IL-6. In IL-6 transgenic mice,which serve as a model for excessive IL-6 production during chronic inflammation,IL-6 may suppress peripherally derived Tregs(iTreg)generation,while may increase and retain self-tolerance by maintaining Foxp3+nTregs development.⁴⁹ In mouse model with elective deletion IL-6R on Tregs (IL-6RaKO), while IL-6R-deficient Tregs maintain immune-suppressive capacity, mice lacking IL-6R on Tregs were more susceptible to inflammatory epithelial injury.⁴⁷ Regarding the underlying mechanisms for PSCI involving IL-6 and Tregs remain to be fully elucidated. It is hypothesized that elevated IL-6 concentrations may provoke a pronounced inflammatory response that suppresses Tregs functional expression increasing fragility to promote PSCI. Nonetheless, this proposed mechanism warrants further empirical validation through comprehensive experimental studies. Consequently, targeting the IL-6 signaling pathway holds considerable promise as a therapeutic strategy for stroke management in the future.

We acknowledge several limitations to the current study. Firstly, longitudinal monitoring of Treg levels and functional activity was not performed. Tregs and IL-6 fluctuate at various time points following AIS. The present investigation examined early expression but did not assess roles of Tregs in the different stroke phases of acute, subacute and chronic. Mechanisms of interaction among other Tregs subsets,IL-10 and TGF-β were not elucidated, particularly within the complex pathological framework of post-stroke cognitive impairment. The safety profile and therapeutic efficacy of Tregs-based interventions require further evaluation prior to clinical translation. The close association between fragile Tregs and severe inflammation highlights the potential for developing novel preventive and therapeutic strategies. Secondly, peripheral venous blood samples were examined but inflammatory cytokine levels in cerebrospinal fluid were not. This omission may limit the accuracy of inferences regarding central nervous system inflammatory status. Lastly, the relatively small sample size and absence of multicenter validation limit interpretations of external validity and generalizability.

Conclusion

Elevated levels of Tregs and IL-6 were predictors of PSCI. IL-6 was identified as having a strong impact on PSD, indicating that both Tregs and IL-6 may be biomarkers for PSCI prediction. IL-6 is a key cytokine that determines the balance of Tregs. While overproduction of IL-6 does not suppressed proliferation of Tregs,it could increasing fragile Tregs in PSCI. Thus,more in-depth studies are needed to elaborate mechanism between IL-6 signaling and fragile Tregs in PSCI. These results may inform early treatment methods and pave the way for development of immunotherapy treatments.