ORIGINAL ARTICLE Year : 2022  |  Volume : 42  |  Issue : 1  |  Page : 34-39

Serum interleukin 15 level may serve as a new marker for alopecia areata

Nehal M Omar1, Bothaina M Ghanem2, Maha Abdelsalam3, Mohammed H Elmogy2
1 Department of Dermatology, Andrology and STDs, Kafr-Elsheikh University Hospital, Kafr-Elsheikh, Egypt
2 Department of Dermatology, Andrology and STDs, Faculty of Medicine, Mansoura University, Egypt
3 Immunology Unit, Department of Clinical Pathology, Faculty of Medicine, Mansoura University, Mansoura; Department of Immunology, Center for Research and Regenerative Medicine, Cairo, Egypt

Date of Submission14-Oct-2020Date of Acceptance09-Dec-2020Date of Web Publication18-Dec-2021

Correspondence Address:
PhD Maha Abdelsalam
Immunology Unit, Department of Clinical Pathology, Faculty of Medicine, Mansoura University, Mansoura, 35516
Egypt

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/ejdv.ejdv_57_20

Background Alopecia areata (AA) is an autoimmune form of nonscarring hair loss that may affect any hair-bearing area. It is one of the most common forms of hair loss seen by dermatologists. The serum level of interleukin 15 (IL-15) is elevated in AA; subsequently, IL-15 limits the suppressive effect of regulatory T cells and activates CD8+NKG2D+ T cells to attack the cells of the hair bulb and initiate AA. Inhibiting IL-15 activity might be a breaking new therapeutic strategy in the treatment of AA.
Patients and methods Serum IL-15 levels were measured by an enzyme-linked immunosorbent assay for 30 patients with active AA (group A), 30 patients with stable AA (group B), and 60 healthy participants of age-matched and sex-matched controls (group C).
Results Serum levels of IL-15 were significantly increased in patients with AA and showed a significant positive correlation with severity (Severity of Alopecia Tool score) and activity of the disease. Receiver operating characteristics curve detected the validity of serum IL-15 in differentiating patients with AA from controls. The best cutoff point for IL-15 was determined to be more than or equal to 7.66 pg/ml, which was able to predict AA with 98.3 sensitivity and 100% specificity. Receiver operating characteristics curve of IL-15 was also conducted to evaluate the sensitivity and specificity of serum IL-15 as a diagnostic index for discrimination between active and stable AA cases, and the best cutoff point for IL-15 was determined to be more than or equal to 21.2 pg/ml, which was able to predict active AA, with 93.3 sensitivity and 100% specificity. Higher IL-15 levels were associated with prediction of severity and activity of AA.
Conclusion Serum IL-15 may represent a new marker for AA diagnosis as well as a predictor of the disease severity and activity.

Keywords: alopecia areata, autoimmune, enzyme-linked immunosorbent assay, interleukin 15

How to cite this article:
Omar NM, Ghanem BM, Abdelsalam M, Elmogy MH. Serum interleukin 15 level may serve as a new marker for alopecia areata. Egypt J Dermatol Venerol 2022;42:34-9
How to cite this URL:
Omar NM, Ghanem BM, Abdelsalam M, Elmogy MH. Serum interleukin 15 level may serve as a new marker for alopecia areata. Egypt J Dermatol Venerol [serial online] 2022 [cited 2021 Dec 18];42:34-9. Available from: http://www.ejdv.eg.net/text.asp?2022/42/1/34/332676   Introduction 

Alopecia areata (AA) is an autoimmune form of nonscarring hair loss that may affect any hair-bearing area [1]. It is one of the most common forms of hair loss seen by dermatologists and accounts for 25% of all the alopecia cases. Its prevalence was estimated at 0.1–0.2%, with a lifetime risk of 1.7% with equal sex incidence [1]. AA is clinically classified according to the extent of hair loss as patchy AA with partial scalp hair loss, AA totalis with complete scalp hair loss, and AA universalis with complete scalp and body hair loss. Clinically, various patterns of hair loss may be observed: patchy, ophiasis, sisaipho (ophiasis inversus), reticulate, and diffuse [2].

Interleukin 15 (IL-15) is a pleiotropic cytokine that functions in NK cell development, lymphocyte homeostasis, and peripheral immune functions. Multiple cell types elaborate IL-15, including activated (e.g. virus infected or bacteria infected) monocytes/macrophages, dendritic cells, and epithelium, as well as constitutive production by bone marrow stromal cells. Antibody-mediated blockade of IL-15 is an effective inhibitor of autoimmunity [3],[4].

The NKG2D-activating ligands and IL-15 can be found in AA hair bulbs and may provide the key response to danger signals that initiate AA [5]. IL-15 is associated with NKG2D upregulation and inhibition of JAK1 and JAK2 in patients with AA, who overexpress IL-15 in their hair follicles (HF). IL-15 stimulates self-reactive memory T cells, which are the main source of interferon gamma (INF-γ), which is mainly responsible for immune privilege (IP) collapse and the AA development [6].

Hypothesis of the study: the serum level of IL-15 is elevated in AA (subsequently, IL-15 limits the suppressive effect of regulatory T cells, and activate CD8+NKG2D+ T cells to attack the cells of the hair bulb and initiate AA).

In this study, we aimed to measure the serum IL-15 levels in patients with AA and to verify if increasing levels may be a useful tool to assess the disease severity and activity.

  Patients and methods 

This study was done as a prospective case–control study that included 30 patients with active AA (group A), 30 patients with stable AA (group B), and 30 healthy participants of matched age and sex as controls (group C). Patients and controls were recruited from the outpatient clinic of Dermatology, Andrology and STDs, Mansoura University Hospitals, between July 2018 and June 2019. All participants gave a written informed consent before participation, and the study protocol was reviewed and approved by the ethics committee of Mansoura Faculty of Medicine (code no MS/18.05.157).

Patients of both sexes, with active and stable AA, aged between 18 and 60 years, with BMI between 18.5 and 24.9 were included. Patients with active AA were those who reported worsening of already existent lesions or the development of new lesions during the previous month. All patients had to refrain from AA treatment for at least 1 month before the study. Patients having personal or family history of AA, autoimmune or systemic disease, pregnant women or women on hormonal contraception, and participants who refused to participate in the study were excluded.

All patients were subjected to history taking and clinical examination. Diagnosis of AA was based on the clinical picture and confirmed by trichoscopy. The pattern of scalp hair loss, nail involvement, and body hair loss were evaluated. Hair-pull test was performed to assess disease activity. The Severity of Alopecia Tool (SALT) score was used for the quantitative assessment of scalp hair loss [7].

Serum concentration of IL-15 was measured using enzyme-linked immunosorbent assay kit (Sunred Biological Technology Co. Ltd, Shanghai, China) according to the manufacturer’s instructions.

Statistical analysis

Statistical analysis of the data was performed using IBM SPSS software package, version 20.0 (IBM Corp., Armonk, New York, USA). Receiver operator characteristic (ROC) curve was used to evaluate the efficacy of serum IL-15 as a diagnostic index for AA, and linear regression was used to predict SALT score by knowing the value of serum IL-15. Significance of the obtained results was judged at the 5% level.

  Results 

The mean age of all studied patients, patients with stable AA, patients with active AA, and control group was 23.3, 25.2, 21.3, and 25.6 years, respectively. All studied patients comprised 38 (63.3%) males and 22 (36.7%) females; stable group had 19 (63.3%) males and 11 (36.7%) females, and active group had 19 (63.3%) males and 11 (36.7%) females. No significant intergroup difference was detected between the mean value for age or sex (P=0.197 and 0.954, respectively). Seven (11.7%) cases had a positive family history, 12 (20%) had history of recurrence, and 30 (50%) had history of stress. No significant differences were found in family history, recurrence, or stress between stable and active cases. A total of 26 (43.3%) of all studied cases had grade 0, 21 (35.0%) cases had grade 1, 10 (16.7%) cases had grade 2, and three (5.0 5) cases had grade 3 pull test. Active cases showed significantly higher grades of pull test. Median SALT score of all studied cases was 6 (range, 0.9–100). Median SALT score in stable cases was 6, whereas its median in active cases was 10. No significant differences were found in SALT score between stable and active groups.

Stable cases were significantly associated with higher frequency of S1, N1, S1B0N1, whereas active cases were significantly associated with higher frequency of N0, S1B0N0. Otherwise, no significant differences were found between stable and active groups regarding Olsen/Canfield classification.

IL-15 was significantly higher in cases (23.5±15.8) when compared with control group (2.8±1.2) (P<0.001) and significantly increased in active (33.9±16.5) when compared with stable group (12.9±3.0) (P<0.001), and there were significant differences among control, stable, and active participants ([Table 1], [Figure 1]).

Table 1 Comparison of interleukin 15 concentration between studied groups

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Figure 1 Box plot of IL-15 concentration in studied groups. The centerline of box denotes the median value; the extremes of the box, the interquartile range; and the bars, the upper and lower limits of 95% of the data. IL-15, interleukin 15.

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The area under the curve-ROC of IL-15 ([Figure 2]) was excellent (0.991). The best cutoff point for IL-15 was determined to be more than or equal to 7.66 pg/ml, which was able to predict AA with 98.3 sensitivity and 100% specificity. ROC curve of IL-15 was conducted to evaluate the sensitivity and specificity of serum IL-15 as a diagnostic index for discrimination between active and stable AA cases. The area under the curve-ROC of IL-15 was excellent (0.988), and the best cutoff point for IL-15 was determined to be more than or equal to 21.2 pg/ml, which was able to predict active AA with 93.3 sensitivity and 100% specificity.

Figure 2 ROC curve of IL-15 (pg/ml) for discrimination between AA and healthy controls. AA, alopecia areata; IL-15, interleukin 15; ROC, receiver operating characteristics.

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IL-15 concentration showed a significant positive correlation with Olsen S, in stable group and significant positive correlations with Olsen S, B, N, and SALT score in active cases. Otherwise, no significant correlations were found in IL-15 with other parameters in stable and active groups ([Table 2]).

Table 2 Correlation of interleukin 15 (pg&z.urule;ml) with other parameters in stable and active groups

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Regression analysis was conducted for prediction of AA within apparently healthy controls, using age, sex, and IL-15 as covariates ([Table 3]). Higher IL-15 was significantly associated with prediction of AA. Generalized linear model showed that higher IL-15 and stress were significant in prediction of higher SALT score within AA cases. In addition, higher IL-15 was considered as independent predictor of active AA.

Table 3 Regression analysis for prediction of alopecia areata within apparently healthy controls

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  Discussion 

Considerable evidence suggests that genetic, immunologic, and environmental factors are involved in AA [8]. Nevertheless, the precise etiopathogenesis of this disease and the relative contributions of these different factors are not fully understood; but it is now clear that the immune system is the major player, with T cells and a collapse of the physiological IP of the HF [9] playing critical roles [10].

IP collapse is a necessary step but not sufficient without the further participation of other immune pathways (e.g. IL-15 and Th17) [11]. Cytokines and chemokines play an important role in the immune process of the disease, and incorrect levels of some cytokines were found in patients with AA, and must be critically implicated in disease pathogenesis [12].

Craiglow and King (2014) and Jabbari et al. (2015) showed that HF gene expression of IL-15, NKG2D ligands, and MHC molecules lead to recruitment and activation of INF-γ-producing, NKG2D-expressing CD8 T cells that target the HF for attack. A positive feedback loop exists in AA, in which skin-infiltrating CD8+NKG2D+ T cells produce IFN-γ, which induces IL-15 and IL-15Rα production by follicular epithelial cells, which in turn activates and sustains the CD8+NKG2D+ effector T-cell response and autoimmunity [5],[13],[14].

IL-15 increases both innate and antigen-specific immune responses and has been implicated in the pathogenesis of several autoimmune diseases [15],[16]. IL-15 stimulates the NKG2D signaling pathway eventually leading to JAK activation [17]. Among its pleiotropic functions, IL-15 acts as a proinflammatory cytokine and stimulates self-reactive memory T cells [6], which are the main source of INF-γ, which is mainly responsible for IP collapse and the AA development.

Upregulation of numerous IFN-regulated genes and of immunostimulatory cytokines such as IL-2 and IL-15 consistently occur in human and C3H/HeJ mice AA lesions [18]. Upregulation of IL-15 and its receptor subunit IL-15Rα in AA HF was also observed in patients with AA [19]. Furthermore, anti-IL-15Rβ antibodies prevented the induction of AA in C3H/HeJ mice [6].

The aim of this study was to evaluate the diagnostic value of IL-15 for AA, to assess its relationship to clinical parameters of the disease, and to examine the possible correlation between serum IL-15 level and disease severity and activity.

The most prevalent risk factor among AA cases in this study was stress (50% of patients). In addition, positive family history was present in 11.7% of cases. The tendency of autoimmune diseases to cluster within families is well documented and is attributable to significant genetic contribution or shared environmental factors.

Active cases showed significantly higher grades of pull test, but no significant differences were found in SALT score between stable and active groups.

The serum IL-15 levels were significantly increased in patients with AA compared with controls and in patients in the active phase of AA compared with those in the stable phase, and in controls. No significant differences were found in IL-15 level according to sex and risk factors in all studied cases.

IL-15 concentration showed a significant positive correlation with activity in all studied cases. Otherwise, no significant correlations were found in IL-15 with other parameters in all studied groups.

ROC curve detected the validity of serum IL-15 in differentiating patients with AA from controls. The best cutoff point for IL-15 was determined to be more than or equal to 7.66 pg/ml, which was able to predict AA, with 98.3% sensitivity and 100% specificity. ROC curve of IL-15 was also conducted to evaluate the sensitivity and specificity of serum IL-15 as a diagnostic index for discrimination between active and stable AA cases. The best cutoff point for IL-15 was determined to be more than or equal to 21.2 pg/ml, which was able to predict active AA with 93.3% sensitivity and 100% specificity.

Higher IL-15 was significantly associated with prediction of AA within apparently healthy controls and was an independent predictor of active AA.

Higher IL-15 and stress were significantly associated with prediction of higher SALT score within AA cases.

The findings of the present study are consistent with those of Ebrahim et al. [20], who showed higher levels of serum IL-15 in patients with AA compared with the control group, and a significant positive correlation was found between SALT score and serum levels of IL-15.

Tabara et al. [21] also reported significantly increased serum IL-15 level in children with AA compared with controls and found that the level of serum IL-15 was increased when the total duration of AA was increased [22].

Association of autoimmune AA with increased IL-15, which is involved in innate immunity, provides links to bacterial and viral infections as triggers of the disease, and might lead to the development of new tools for prevention such as vaccines, as well as help to identify potential therapeutic targets for this psychologically devastating disorder.

  Conclusion 

The significantly higher levels of serum IL-15 in patients with AA suggest a possible role of IL-15 as a proinflammatory cytokine in the pathogenesis of AA and indicate that it could be used as a diagnostic marker of AA as well as a prognostic marker for its severity and predict its activity. Therapeutic manipulations targeting IL-15 should be evaluated as a source of possible therapeutic modalities for the treatment of recalcitrant AA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

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  [Table 1], [Table 2], [Table 3]