Soluble granzyme B and cytotoxic T lymphocyte activity in the pathogenesis of systemic lupus erythematosus Dilip Shah a , Ravi Kiran a , Ajay Wanchu b , Archana Bhatnagar a,⇑ a Department of Biochemistry, Basic Medical Sciences Block, Panjab University, Chandigarh, India b Division of Arthritis and Rheumatic Diseases-OP09, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA article info Article history: Received 15 January 2011 Accepted 7 March 2011 Available online 12 March 2011 Keywords: Soluble granzyme B Cytotoxic T lymphocyte SLEDAI score Systemic lupus erythematosus abstract Activated cytotoxic T lymphocyte (CTL) mediated target cell death has been implicated in the develop- ment of systemic autoimmune disease like SLE. However, the role of soluble granzyme B and its relation- ship with CTL activity and disease activity is still unknown. In this study, we evaluated role of soluble granzyme B and cytotoxic T lymphocyte activity in SLE patients. The soluble granzyme B was measured in the serum by an enzyme-linked immunosorbent assay while cytotoxic T lymphocyte activity was mea- sured by flow cytometry. The disease activity was determined by using SLE Disease Activity Index (SLE- DAI) score. Cytotoxic T lymphocyte activity was increased and strongly associated with disease activity. The soluble granzyme B levels were higher in SLE patients and associated with various clinical features like reduced complement components; C3 & C4 and skin lesion. The soluble granzyme B levels were also sturdily related with severity of the disease. The findings of this study suggest that excessive secretion of soluble granzyme B and enhanced activity of cytotoxic T lymphocyte may play a vital role in the patho- genesis of SLE and organ damage. Also, evaluation of soluble granzyme B may be helpful in monitoring the clinical features associated with activated CTL in SLE. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction Systemic lupus erythematosus is a multi-system autoimmune disease characterized by the presence of autoantibodies, especially against nuclear components. A key issue in the pathogenesis of lu- pus is how intracellular antigens become exposed and targeted by the immune system. The heterogeneous nature of disease suggests that numerous factors may be involved in generating the auto- antigens that are associated with SLE. Lymphocyte apoptosis has been invoked in this regard. This is supported by the observations that SLE patients show increased apoptosis of PBMCs, especially T lymphocytes [1,2], and decreased clearance of activated T cells [3]. A defect in control of apoptosis and delayed clearance of apoptotic cells may provide sustained interaction between reactive oxygen species and apoptotic cell macromolecules generating neoepitopes resulting in autoantibody formation in autoimmune diseases [4]. There is growing evidence that structural changes of auto-anti- gens during cytotoxic lymphocyte granule-mediated cell death by perforin and granzyme B is a dominant feature of SLE [5]. Gran- zyme B is a serine protease found in the cytoplasmic granules of CTLs and natural killer (NK) cells that plays an important role in inducing apoptotic changes in target cells during granule exocyto- sis-induced cytotoxicity. When granzyme B is secreted into the cytoplasm of target cell through the pore formed by perforin, it triggerscytotoxic induced cell death [6–8]. Recent study shows that granzyme B cleaves auto-antigens that are targeted across the spectrum of systemic autoimmune disease, producing unique auto-antigen fragments that are not seen during caspase-mediated or other forms of cell death. These reports high- light the role of granzyme B as a major contributor to the genera- tion of novel, immunogenic epitopes in autoimmune disease [9,10]. The role of CD8 + cytotoxic T lymphocyte as a generation of auto-antigen in SLE patients is well documented in the previous studies. The histological studies on discoid lupus erythematosus reveal that skin lesions is predominantly composed of T lympho- cytes, with a slight predominance of CD4 + over CD8 + T cells [11,12]. Until recently, Granzyme B was widely studied at intracellular level, especially in context with apoptosis in SLE [13]. However, the granzymes were originally identified as both intracellular and extracellular proteases, and over the past few years, vast research aims on extracellular Granzyme B activity in autoimmune diseases 0008-8749/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.cellimm.2011.03.004 Abbreviations: SLE, systemic lupus erythematosus; PBMC, peripheral blood mononuclear cells; CTL, cytotoxic T lymphocyte; NK, natural killer; SLEDAI, Systemic Lupus Erythematosus Disease Activity Index; ESR, erythrocyte sedimen- tation rate; C3, complement component 3; C4, complement component 4. ⇑ Corresponding author. Address: Department of Biochemistry, Basic Medical Science Building, Panjab University, Chandigarh 160014, India. Fax: +91 172 2541022. E-mail address: bhatnagar.archana@gmail.com (A. Bhatnagar). Cellular Immunology 269 (2011) 16–21 Contents lists available at ScienceDirect Cellular Immunology journal homepage: www.elsevier.com/locate/ycimm