近年来,低剂量白细胞介素-2(interleukin-2,IL-2)在治疗自身免疫性疾病方面的作用受到广泛关注,国内外在IL-2机制与临床方面进行了一系列深入的研究。研究证明,高剂量IL-2促进细胞毒T细胞和自然杀伤细胞的增殖,而低剂量IL-2则对免疫系统起抑制作用。低剂量IL-2的主要作用机制并非激活效应性T细胞,而是通过对调节性T细胞(regulatory T cell,Treg)的激活,抑制免疫系统过度活化。目前已有多项临床试验结果显示,低剂量IL-2对于多种自身免疫性疾病,如系统性红斑狼疮(systemic lupus erythematosus,SLE)、血管炎及炎性肌病等有效[1,2,3]。本文旨在对低剂量IL-2对CD4+T细胞亚群的调节作用及其在治疗自身免疫性疾病中的作用进行评价。
1. IL-2是免疫稳态维持的关键分子
IL-2主要由CD4+T细胞产生,其他免疫细胞如CD8+T细胞、自然杀伤细胞(natural killer cell,NK cells)等也可产生少量的IL-2。IL-2于1976年被发现,其能够维持T细胞在体外的长期生长,故被称为T细胞生长因子[4]。1979年第二届国际淋巴因子研讨会统一将其命名为IL-2[5]。IL-2通过白细胞介素-2受体(IL-2 receptor, IL-2R)发挥其生理作用,IL-2R是一组不同的复合体,按其对IL-2亲和力不同被分为低、中、高亲和力受体,这些受体均由IL-2Rα(即CD25)、IL-2Rβ(即CD122)、IL-2Rγ(即CD132)三种亚基中的一个或多个亚基构成。
IL-2可以通过对Treg细胞与辅助性T细胞(helper T cell,Th)17的平衡的调节影响细胞免疫过程。Treg细胞通常指的是CD4+CD25+Foxp3+Treg细胞,该类Treg细胞直接从胸腺分化发育而来,初始CD4+T细胞在转化生长因子β(transforming growth factor-β,TGF-β)的作用下,分化为Treg细胞[6],进一步Treg细胞可以通过接触抑制或分泌抑制性细胞因子发挥抑制免疫应答的作用[7]。Th17细胞是Harrington等[8]从Th1、Th2细胞中分化的细胞亚群中发现一种分泌IL-17的新型CD4+T细胞亚群,主要通过分泌IL-17等细胞因子,在免疫损伤,特别是自身免疫性疾病的发病中起到重要作用。
早期研究中,人们仅认识到了IL-2对T细胞的激活作用,这与不同种类IL-2R在T细胞各亚型的分布有关。Treg细胞更多表达高亲和力的IL-2Rαβγ,而效应性T细胞(effector T cell,Teff)中更多表达中等亲和力的IL-2βγ,这造成Treg细胞对较低剂量的IL-2更为敏感,低剂量IL-2刺激Treg细胞增殖活化,进而抑制免疫系统过度激活;而相对高浓度的IL-2能激活Teff细胞,促进免疫激活[9]。经研究证明,低剂量的IL-2可以抑制IL-17的增殖分化[10]。
除对细胞免疫稳态的维持作用外,IL-2也可以通过对滤泡辅助性T细胞(follicular helper T cells,Tfh)的调节影响体液免疫过程。研究显示[2],IL-2能有效抑制Tfh细胞的分化,进而抑制体液免疫的过度激活。
2. 低剂量IL-2可改善免疫稳态失衡
Th17细胞的异常活化和Treg细胞的抑制可造成Treg/Th17失衡,Treg/Th17细胞亚群失衡是自身免疫性疾病的重要特征,在疾病发生、发展过程中起到重要作用,同时可作为患者体内免疫系统活化情况的监测指标[11]。低剂量IL-2可以通过促进Treg细胞增殖分化而抑制Th17细胞,改善自身免疫性疾病中Treg/Th17细胞失衡。
除了细胞免疫失衡,体液免疫受损也是自身免疫性疾病的重要特征,而这其中Tfh细胞发挥了重要作用。我们前期的临床试验也发现,经过低剂量的IL-2治疗,自身免疫性疾病患者体内的Tfh细胞受到明显抑制[2]。动物实验表明,活化的CD4+T细胞向淋巴结外T细胞区迁移,激活的树突状细胞产生膜结合和可溶性的CD25,以抑制T细胞衍生的IL-2和增强Tfh细胞分化[12],因此,低剂量IL-2对Tfh细胞的抑制作用可能发生在Tfh细胞分化的早期。
3. 低剂量IL-2在自身免疫性疾病中的临床应用
3.1. 低剂量IL-2在系统性红斑狼疮治疗中的应用
近年来,我们和其他研究者的研究显示,SLE患者血清IL-2浓度较健康人低,且降低程度与狼疮肾炎的发生相关[13];SLE患者外周血Treg细胞比例降低而Th17细胞比例升高的现象也已被观察证实,其变化程度与SLE疾病活动度指数(SLE disease activity index,SLEDAI)等疾病活动度评分显著相关[14]。基于这些现象,我们设计完成了关于IL-2治疗SLE的临床试验[1,2],对IL-2治疗SLE的临床疗效、安全性等分别进行了验证。在免疫学方面,IL-2治疗后(剂量和疗程为隔日100万IU,每连续用药2周后停药2周,共持续12周), 患者的外周血Treg细胞比例明显升高,而Th17、Tfh细胞比例下降;同时在临床症状方面,皮疹、脱发、尿蛋白等影响SLE患者的主要症状均可见明显的改善。
3.2. 低剂量IL-2在其他自身免疫性疾病中的应用
随着低剂量IL-2免疫调控机制的研究不断深入,IL-2在多种免疫相关的疾病中得到重视(表1),如移植物抗宿主病(graft versus-host disease,GVHD)[15,16]、丙型肝炎相关的血管炎[17]和1型糖尿病[18]。Zhang等[19,20]在4例免疫性血小板减少性紫癜中应用低剂量IL-2可提高患者血小板计数。Castela等[21]在5例斑秃患者中应用IL-2,剂量为150万IU/d连用5 d,此后每三周300万IU/d连用5 d,患者斑秃皮损面积得到显著缩小,而外周血Treg细胞增加,且在皮肤活检中亦发现Treg细胞增加。Miao等[22]研究发现小剂量IL-2可促进干燥综合征(Sjögren’s syndrome,SS)患者体内Treg和Th17的平衡。Zhang等[23]在炎性肌病中应用IL-2,在接受50万IU IL-2治疗5 d后,患者Treg细胞显著增加,同时红细胞沉降率、肌酶及疼痛评分均显著下降。另外,Rosenzwajg等[3]近期发表的临床研究显示,低剂量IL-2对类风湿关节炎(rheumatoid arthritis,RA)、强直性脊柱炎(ankylosing spondylitis,AS)等11种自身免疫性疾病均安全有效。我们近期完成的低剂量IL-2治疗SS和RA的双盲临床试验(NCT02464319, NCT02467504),进一步证明了该治疗方法对于自身免疫性疾病有很好的疗效。目前多种自身免疫性疾病或免疫相关疾病的低剂量IL-2疗法的临床试验尚待发表(表2)。
1.
已发表的低剂量IL-2治疗自身免疫性疾病的临床试验
Published clinical trials of low dose IL-2 in the treatment of autoimmune diseases
| Diseases | Daily dose/(Million IU) | Clinical efficacy | Immunological changes | References |
| SLE, systemic lupus erythematosus; SS, Sjögren syndrome; AS, ankylosing spondylitis; DM/PM, dermatomyositis/polymyositis; GVHD, graft versus-host disease; HCV, hepatitis C virus; T1DM, type 1 diabetes; ITP, immune thrombocytopenia; RA, rheumatoid arthritis; SLEDAI, systemic lupus erythematosus disease activity index; BASDAI, Bath ankylosing spondylitis disease activity index; CK, creatine kinase; PLT, platelet; Treg, regulatory T cell; Th, helper T cell; Tfh, follicular helper T cell; NK, natural killer cell; Teff, effector T cell. | ||||
| SLE | 1 | SLEDAI↓ | Treg↑,Th17 ↓, Tfh↓, NK↑,CD56brightNK↑ |
He et al.(2016,2019)[1,2] |
| SS | 1.5 | Not evaluated | Treg↑,Th17↓ | Miao et al.(2018)[22] |
| AS | 0.5 | BASDAI↓ | Treg↑,Th17/Treg↓ | An et al.(2019)[24] |
| DM/PM | 0.5 | CK↓ | Treg↑ | Zhang et al.(2019)[23] |
| GVHD | 0.3/1/3 per m2 | Rash↓ | Treg↑ | Betts et al.(2017)[15] Zhao et al.(2016)[16] |
| HCV-induced vasculitis | 1.5 | Vasculitis↓ | Treg↑,NK↑,CD56brightNK↑ | Saadoun et al.(2011)[17] |
| T1DM | 0.33/1/3 | Not evaluated | Treg↑ | Hartemann et al.(2013)[18] |
| ITP | 1 | PLT↑ | Treg↑ | Zhang et al.(2018)[19, 20] |
| Alopecia areata | 1.5 | Hair loss area↓ | Treg↑,Teff↓ | Castela et al.(2014)[21] |
| 11 kinds of autoimmune diseases such as RA | 1 | Effective | Treg↑ | Rosenzwajg et al.(2019)[3] |
2.
已完成但尚未发表的低剂量IL-2治疗自身免疫性疾病的临床试验
Clinical trial of low-dose IL-2 for the treatment of autoimmune diseases that has been completed but not yet published
| Disease | Year | Type | Number | Country |
| RA, rheumatoid arthritis; SS, Sjögren syndrome; CKD, chronic kidney disease; SLE, systemic lupus erythematosus. | ||||
| RA | 2016 | Single-center | 47 | China |
| SS | 2016 | Single-center | 60 | China |
| Multiple sclerosis | 2016 | Single-center | 30 | France |
| Hemolytic anemia | 2017 | Single-center | 2 | France |
| CKD | 2016 | Single-center | 10 | China |
| SLE | 2017 | Multi-center | 100 | France etc. |
| Amyotrophic lateral sclerosis | 2015 | Single-center | 36 | France |
3.3. 低剂量IL-2与感染免疫
相比于其他生物制剂会增加感染风险,低剂量IL-2在临床中并未表现出增加感染的风险。在我们的IL-2治疗SLE的临床试验中[1,2],IL-2治疗组感染风险非但没有升高,反而低于对照组。治疗组3例患者分别在入组时合并不同种类的病毒感染,经IL-2治疗后,在SLE病情缓解的同时,病毒载量也同时降低。在肝炎方面,Saadoun等[17]研究证实,IL-2在治疗丙型肝炎相关的血管炎时,并未激活患者体内的丙型肝炎病毒。对于肝炎、结核患者,应用常规生物制剂时受限很大,而越来越多的证据表明,IL-2对合并此类感染的自身免疫性疾病患者亦较为安全。另外,我们还在进一步研究低剂量IL-2调节感染免疫的机制,初步的研究显示,低剂量IL-2可以明显增加流行性感冒病毒感染的小鼠的生存期和体质量,但尚需进一步明确。
4. 展望
目前,自身免疫性疾病的治疗主要依赖糖皮质激素、免疫抑制剂等传统药物。糖皮质激素长期应用,可造成患者骨质疏松、内分泌代谢紊乱等不良反应;多数传统免疫抑制剂长期大量应用可能对患者肝、肾功能造成损伤,甚至可造成骨髓抑制、性腺抑制等严重不良反应;新型生物制剂如肿瘤坏死因子α抑制剂、CD20单克隆抗体等属非适应证用药,仅用于少数患者,且感染风险也升高。
低剂量IL-2治疗旨在通过提升Treg细胞数量,降低效应性T细胞功能,进而调节免疫稳态,抑制免疫系统过度激活以达到治疗效果,现已在多种自身免疫性疾病中得到应用。多数IL-2缺乏、Treg细胞抑制的免疫相关疾病均可能从IL-2治疗中受益。除在风湿免疫领域外,低剂量IL-2在皮肤科、神经内科、内分泌科等多个学科领域中均已有研究发表,可能有很大的临床应用前景。
越来越多的研究证明,低剂量IL-2在治疗自身免疫性疾病的同时可降低患者感染风险,IL-2在感染免疫中的调节机制研究可能是IL-2治疗领域研究的热点之一。
目前已有多项临床研究提示,低剂量IL-2具有明确的治疗效果,安全性好,同时不少临床研究正在进行中,将为自身免疫性疾病的治疗提供更多的临床依据。
References
- 1.He J, Zhang R, Shao M, et al. Efficacy and safety of low-dose IL-2 in the treatment of systemic lupus erythematosus: A randomised, double-blind, placebo-controlled trial[J/OL]. Ann Rheum Dis, 2019, 9(2019-09-19)[2019-10-01]. https://www.ncbi.nlm.nih.gov/pubmed?term=Efficacy+and+safety+of+low-dose+IL-2+in+the+treatment+of+systemic+lupus+erythematosus%3A+a+randomised%2C+double-blind%2C+placebo-controlled+trial&TransSchema=title&cmd=detailssearch.
- 2.He J, Zhang X, Wei Y, et al. Low-dose interleukin-2 treatment selectively modulates CD4(+) T cell subsets in patients with systemic lupus erythematosus. Nat Med. 2016;22(9):991–993. doi: 10.1038/nm.4148. [DOI] [PubMed] [Google Scholar]
- 3.Rosenzwajg M, Lorenzon R, Cacoub P, et al. Immunological and clinical effects of low-dose interleukin-2 across 11 autoimmune diseases in a single, open clinical trial. Ann Rheum Dis. 2019;78(2):209–217. doi: 10.1136/annrheumdis-2018-214229. [DOI] [PubMed] [Google Scholar]
- 4.Morgan DA, Ruscetti FW, Gallo R. Selective in vitro growth of T lymphocytes from normal human bone marrows. Science. 1976;193(4257):1007–1008. doi: 10.1126/science.181845. [DOI] [PubMed] [Google Scholar]
- 5.Mizel SB, Farrar JJ. Revised nomenclature for antigen-nonspecific T-cell proliferation and helper factors. Cell Immunol. 1979;48(2):433–436. doi: 10.1016/0008-8749(79)90139-4. [DOI] [PubMed] [Google Scholar]
- 6.Shao Q, Gao H. Progress in interleukin-2 therapy for rheumatic immune diseases by regulating the immune balance of T cells[J/OL]. Scand J Immunol, 2019, 9(2019-09-08)[2019-10-01]. https://www.ncbi.nlm.nih.gov/pubmed?term=Progress+in+Interleukin-2+therapy+for+rheumatic+immune+diseases+by+regulating+the+immune+balance+of+T+cells&TransSchema=title&cmd=detailssearch.
- 7.Sakaguchi S, Wing K, Miyara M. Regulatory T cells: A brief history and perspective. Eur J Immunol. 2007;37(Suppl 1):116–123. doi: 10.1002/eji.200737593. [DOI] [PubMed] [Google Scholar]
- 8.Harrington LE, Hatton RD, Mangan PR, et al. Interleukin 17-producing CD4+effector T cells develop via a lineage distinct from the T helper type 1 and 2 lineages . Nat Immunol. 2005;6(11):1123–1132. doi: 10.1038/ni1254. [DOI] [PubMed] [Google Scholar]
- 9.Zhao Z, Zhang X, Su L, et al. Fine tuning subsets of CD4+T cells by low-dosage of IL-2 and a new therapeutic strategy for autoimmune diseases . Int Immunopharmacol. 2018;56:269–276. doi: 10.1016/j.intimp.2018.01.042. [DOI] [PubMed] [Google Scholar]
- 10.Kim HS, Jang SW, Lee W, et al. PTEN drives Th17 cell differentiation by preventing IL-2 production. J Exp Med. 2017;214(11):3381–3398. doi: 10.1084/jem.20170523. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Osnes LT, Nakken B, Bodolay E, et al. Assessment of intracellular cytokines and regulatory cells in patients with autoimmune diseases and pri-mary immunodeficiencies: Novel tool for diagnostics and patient follow-up. Autoimmun Rev. 2013;12(10):967–971. doi: 10.1016/j.autrev.2013.02.003. [DOI] [PubMed] [Google Scholar]
- 12.Li J, Lu E, Yi T, et al. EBI2 augments Tfh cell fate by promoting interaction with IL-2-quenching dendritic cells. Nature. 2016;533(7601):110–114. doi: 10.1038/nature17947. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Shao M, He J, Zhang R, et al. Interleukin-2 deficiency associated with renal impairment in systemic lupus erythematosus. J Interferon Cytokine Res. 2019;39(2):117–124. doi: 10.1089/jir.2018.0016. [DOI] [PubMed] [Google Scholar]
- 14.Shin MS, Lee N, Kang I. Effector T-cell subsets in systemic lupus erythematosus: Update focusing on Th17 cells. Curr Opin Rheumatol. 2011;23(5):444–448. doi: 10.1097/BOR.0b013e328349a255. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Betts BC, Pidala J, Kim J, et al. IL-2 promotes early Treg reconstitution after allogeneic hematopoietic cell transplantation. Haematologica. 2017;102(5):948–957. doi: 10.3324/haematol.2016.153072. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Zhao XY, Zhao XS, Wang YT, et al. Prophylactic use of low-dose interleukin-2 and the clinical outcomes of hematopoietic stem cell transplantation: A randomized study. Oncoimmunology. 2016;5(12):e1250992. doi: 10.1080/2162402X.2016.1250992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Saadoun D, Rosenzwajg M, Joly F, et al. Regulatory T-cell responses to low-dose interleukin-2 in HCV-induced vasculitis. N Engl J Med. 2011;365(22):2067–2077. doi: 10.1056/NEJMoa1105143. [DOI] [PubMed] [Google Scholar]
- 18.Hartemann A, Bensimon G, Payan CA, et al. Low-dose interleukin 2 in patients with type 1 diabetes: a phase 1/2 randomised, double-blind, placebo-controlled trial. Lancet Diabetes Endocrinol. 2013;1(4):295–305. doi: 10.1016/S2213-8587(13)70113-X. [DOI] [PubMed] [Google Scholar]
- 19.Zhang J, Ruan Y, Shen Y, et al. Low dose IL-2 increase regulatory T cells and elevate platelets in a patient with immune thrombocytopenia. Cytometry B Clin Cytom. 2018;94(3):400–404. doi: 10.1002/cyto.b.21494. [DOI] [PubMed] [Google Scholar]
- 20.Zhang J, Ruan Y, Xu X, et al. Therapeutic potential of low-dose IL-2 in immune thrombocytopenia: An analysis of 3 cases. Cytom B Clin Cytom. 2018;94(3):428–433. doi: 10.1002/cyto.b.21601. [DOI] [PubMed] [Google Scholar]
- 21.Castela E, Le Duff F, Butori C, et al. Effects of low-dose recombinant interleukin 2 to promote T-regulatory cells in alopecia areata. JAMA Dermatol. 2014;150(7):748–751. doi: 10.1001/jamadermatol.2014.504. [DOI] [PubMed] [Google Scholar]
- 22.Miao M, Hao Z, Guo Y, et al. Short-term and low-dose IL-2 therapy restores the Th17/Treg balance in the peripheral blood of patients with pri-mary Sjögren’s syndrome. Ann Rheum Dis. 2018;77(12):1838–1840. doi: 10.1136/annrheumdis-2018-213036. [DOI] [PubMed] [Google Scholar]
- 23.Zhang S, Wang J, Sun H, et al. Circulating regulatory T cells were absolutely decreased in dermatomyositis/polymyositis patients and restored by low-dose IL-2[J/OL]. Ann Rheum Dis, 2019, 10(2019-10-14)[2019-10-16]. https://www.ncbi.nlm.nih.gov/pubmed?term=Circulating+regulatory+T+cells+were+absolutely+decreased+in+dermatomyositis/polymyositis+patients+and+restored+by+low-dose+IL-2&TransSchema=title&cmd=detailssearch.
- 24.An H, Li X, Li F, et al. The absolute counts of peripheral T lymphocyte subsets in patient with ankylosing spondylitis and the effect of low-dose interleukin-2. Medicine (Baltimore) 2019;98(15):e15094. doi: 10.1097/MD.0000000000015094. [DOI] [PMC free article] [PubMed] [Google Scholar]