Regulatory T cells (Tregs) play a crucial role in maintaining immune tolerance. Any deficiency or dysfunction of the Tregs can influence the pathogenesis of autoimmune disease. This study aimed to assess the role of Tregs among patients with autoimmune encephalitis (AE) with different autoantibody types and to evaluate their association with clinical features.
This was a cross-sectional observational study involving 29 patients with AE. Peripheral blood was sampled from each patient for flow cytometric analysis. Proportions of CD4+CD25+ and CD4+CD25+Foxp3+ Tregs were calculated and compared between the antibody types (synaptic, paraneoplastic, and undetermined). Associations between the proportion of Tregs and clinical features were also evaluated.
Five patients had synaptic autoantibodies, five had paraneoplastic autoantibodies, and the others were of an undetermined type. The proportion of CD4+CD25+ Tregs tended to be higher in those with paraneoplastic antibodies than in those with synaptic antibodies (
The results of the present study suggest that Tregs may play different roles according to the type of AE and may be linked to disease severity.
Autoimmune encephalitis (AE) causes focal or diffuse neural inflammation mediated by autoantibodies [
Regulatory T cells (Tregs) are known to suppress inflammatory autoimmune responses [
AE also occurs when the CNS immune system becomes dysregulated. The proportion of Tregs, which suggests the maintenance of immune tolerance, may be involved in the pathogenesis of AE and may differ between the autoantibody types. Thus, in the present study, we compared proportions of Tregs between different antibody types and evaluated their association with clinical characteristics in patients with AE.
Thirty patients diagnosed with AE were enrolled between January 2017 and July 2018. The study inclusion criteria were based on established criteria for diagnosing AE [
Clinical characteristics, including the modified Rankin scale (mRS) values and the Clinical Assessment Scale in Autoimmune Encephalitis (CASE) score [
This study was approved by the Institutional Review Board of Seoul National University Hospital (No. 1603-047-747). Written informed consent to participate was obtained from the patients enrolled or their next of kin.
About 10 mL of venous blood was collected from each patient into heparin-anticoagulated vacuum tubes, and peripheral blood mononuclear cell (PBMC) preparation was conducted on the same day as sampling. The PBMCs were incubated with a cocktail containing anti-human CD4+ and CD25+ for 30 minutes at room temperature and then were stained for fluorescence-activated cell sorting. The percentages of CD4+CD25+ cells and CD4+CD25+Foxp3+ cells were calculated using the FACSCalibur software program (BD Biosciences, San Jose, CA, USA).
The Kruskal-Wallis test was used to compare Treg proportions between the three antibody groups. The Mann-Whitney U-test was used for post-hoc analysis to determine the significance of the differences between pairs of groups. Categorical variables were compared using Fisher exact test. Spearman correlation coefficient was used to examine correlations between Treg proportions and clinical variables, and the level of significance was set at p < 0.05. For the
A total of 29 patients, including five with synaptic antibodies (i.e., four with anti-
The mean PBMC count was 157.2 × 105 cells/mL and was also similar between the groups. The mean proportions of CD4+CD25+ and CD4+CD25+Foxp3+ Tregs were 8.8% ± 4.9% and 1.8% ± 1.9%. The proportion of CD4+CD25+ Tregs tended to be higher in those with paraneoplastic antibodies than in those with an undetermined antibody status (
A significant negative correlation was observed between the proportion of Tregs (CD4+CD25+Foxp3+) and the initial mRS value (r = −0.391, p = 0.036) (
The results of the present study suggest that the role of Tregs may vary with autoantibody type in AE. Those with paraneoplastic antibodies tended to present higher Treg proportions than those with synaptic antibodies. The proportion of Tregs was negatively correlated with initial disease severity and differed between those who were treated with IVIg and those who were not, which may be further used as a biomarker for disease activity.
Although the proportion of CD4+CD25+ Tregs tended to be different between AE patients with different antibody types, no difference was found in the proportion of CD4+CD25+Foxp3 Tregs. Foxp3 plays a crucial role in the development and function of Tregs and is considered one of the most reliable markers of Tregs [
Variable proportions of Tregs among AE patients with different antibody types may suggest different pathophysiologies. AE patients with paraneoplastic antibodies usually have no pathogenic role, but their condition involves cytotoxic T cells that directly cause neuronal impairment. In contrast, T-cell involvement in those with synaptic antibodies is unclear. Synaptic antibodies bind to neuronal cell surface receptors and alter synaptic signaling processes [
The proportion of Tregs was also negatively associated with functional status in AE patients, with lower Treg proportions correlating with higher mRS values. In line with our study, the frequency of Tregs was found by Correale and Villa [
Treg proportions differed according to IVIg treatment but not rituximab treatment. IVIg therapy can increase cytokine secretions to enhance immune tolerance [
The results of our study should also be interpreted cautiously in light of their limitations. This study was a single-center investigation considering a relatively small number of AE patients without a comparison with healthy controls. Because this was a cross-sectional study, the time and type of immunotherapy were not controlled, which may have influenced our findings.
In conclusion, this study suggests different roles of Tregs exist according to autoantibody type in patients with AE. Moreover, it proposes novel therapeutic models for AE by expanding the numbers of immunoregulatory and anti-inflammatory Tregs. Future prospective longitudinal research is necessary to confirm the role of Tregs in AE and the response to immunotherapy.
Jangsup Moon, Soon-Tae Lee, Keun-Hwa Jung, Kyung-Il Park, Sang Kun Lee, Kon Chu have been editorial board of
Conceptualization: JI Byun, J Moon, K Chu; Data curation: JI Byun; Formal analysis: JI Byun, JY Bae; Resources, Funding acquisition: K Chu; Methodology, Investigation: JY Bae; Project administration: JI Byun, K Chu; Supervision: J Moon, ST Lee, KH Jung, KI Park, M Kim, SK Lee, K Chu; Writing - original draft: JI Byun; Writing - review & editing: J Moon, ST Lee, KH Jung, KI Park, M Kim, SK Lee.
This study was supported by JW Pharma and Yuhan Corporation (06-2020-1110).
Treg, regulatory T-cell; mRS, modified Rankin scale.
Clinical characteristics of patients with autoimmune encephalitis according to autoantibody type
Characteristic | Undetermined | Synaptic | Paraneoplastic | p-value |
---|---|---|---|---|
No. of patients | 19 | 5 | 5 | |
Age (yr) | 47.9 ± 17.8 | 36.2 ± 19.5 | 52.8 ± 16.1 | 0.325 |
Male sex | 7 (36.8) | 1 (20.0) | 2 (40.0) | 0.749 |
Disease duration (mo) | 30.9 ± 47.5 | 9.5 ± 9.9 | 24.1 ± 13.8 | 0.287 |
Follow-up duration (mo) | 18.4 ± 14.8 | 6.8 ± 8.6 | 17.0 ± 8.9 | 0.180 |
mRS value | ||||
Initial | 2.4 ± 1.0 | 3.2 ± 1.1 | 3.0 ± 0.7 | 0.164 |
Follow-up | 1.8 ± 1.2 | 2.4 ± 1.5 | 2.8 ± 1.9 | 0.499 |
CASE score | ||||
Initial | 4.8 ± 3.8 | 8.0 ± 4.6 | 4.4 ± 1.7 | 0.094 |
Follow-up | 3.4 ± 4.1 | 5.8 ± 4.8 | 2.5 ± 1.3 | 0.168 |
Treatment received | ||||
Immunotherapy | 11 (57.9) | 5 (100) | 5 (100) | 0.055 |
IV steroid | 3 (15.8) | 4 (80.0) | 2 (40.0) | 0.020 |
IVIg | 11 (57.9) | 4 (80.0) | 4 (80.0) | 0.492 |
Rituximab | 4 (21.1) | 2 (40.0) | 3 (60.0) | 0.220 |
Values are presented as mean ± standard deviation or number (%).
mRS, modified Rankin scale; CASE, Clinical Assessment Scale in Autoimmune Encephalitis; IV, intravenous; IVIg, IV immunoglobulin.
Flow cytometry results of patients with autoimmune encephalitis according to autoantibody type
Variable | Undetermined (n = 19) | Synaptic (n = 5) | Paraneoplastic (n = 5) | p-value |
---|---|---|---|---|
WBC (/μL) | 7,215 ± 2,592 | 6,062 ± 1,400 | 6,468 ± 1,847 | 0.586 |
ANC (/μL) | 4,647 ± 2,551 | 3,810 ± 1,596 | 4,019 ± 1,804 | 0.865 |
PBMC (×105/mL) | 160.4 ± 126.9 | 124.6 ± 78.3 | 178.0 ± 143.4 | 0.838 |
CD4+CD25+ (%) | 8.2 ± 5.1 | 7.3 ± 3.5 | 12.8 ± 3.4 | 0.073 |
CD4+CD25+Foxp3+ (%) | 1.7 ± 1.8 | 1.5 ± 1.7 | 2.6 ± 2.3 | 0.319 |
Foxp3/CD4+ (%) | 26.7 ± 24.5 | 17.1 ± 11.0 | 19.7 ± 15.2 | 0.769 |
Values are presented as mean ± standard deviation.
WBC, white blood cell count; ANC, absolute neutrophil count; PBMC, peripheral blood mononuclear cell count; Foxp3, forkhead box P3.
Proportions of peripheral regulatory T cells in patients who received IVIg and those who did not
Variable | No IVIg (n = 10) | Received IVIg (n = 19) | p-value |
---|---|---|---|
CD4+CD25+ (%) | 10.4 ± 6.0 | 8.0 ± 4.1 | 0.271 |
CD4+CD25+Foxp3+ (%) | 3.2 ± 2.5 | 1.1 ± 0.8 | 0.029 |
Foxp3/CD4+ (%) | 39.3 ± 27.7 | 15.7 ± 10.9 | 0.031 |
Values are presented as mean ± standard deviation.
IVIg, intravenous immunoglobulin; Foxp3, forkhead box P3.