Regulatorische T-Zellen und rheumatische Erkrankungen

Dysregulation and chronicity of pathogenic T cell responses in the pre-diseased stage of lupus

In the normal immune system, T cell activation is tightly regulated and controlled at several levels to ensure that activation occurs in the right context to prevent the development of pathologic conditions such as autoimmunity or other harmful immune responses. CD4+FoxP3+ regulatory T cells (Treg) are crucial for the regulation of T cell responses in the peripheral lymphatic organs and thus for the prevention and control of autoimmunity. In systemic lupus erythematosus (SLE), a prototypic systemic autoimmune disease with complex etiology, a disbalance between Treg and pathogenic effector/memory CD4+ T cells develops during disease progression indicating that gradual loss of control over T cell activation is an important event in the immune pathogenesis. This progressive failure to adequately regulate the activation of autoreactive T cells facilitates chronic activation and effector/memory differentiation of pathogenic T cells, which are considered to contribute significantly to the induction and perpetuation of autoimmune processes and tissue inflammation in SLE. However, in particular in humans, little is known about the factors which drive the escape from immune regulation and the chronicity of pathogenic T cell responses in an early stage of autoimmune disease when clinical symptoms are still unapparent. Here we briefly summarize important findings and discuss current views and models on the mechanisms related to the dysregulation of T cell responses which promotes chronicity and pathogenic memory differentiation with a focus on the early stage of disease in lupus-prone individuals.

Restoring regulation - IL-2 therapy in systemic lupus erythematosus

INTRODUCTION

The pathogenesis of systemic lupus erythematosus (SLE) involves an acquired deficiency of the cytokine IL-2, an essential growth and survival factor for regulatory T cells (Treg), which play an important role in the control of autoimmunity in SLE. In contrast to currently available therapies that broadly suppress the immune system, low-dose IL-2 therapy in SLE aims to compensate the pre-existing IL-2 deficiency and thus to restore a physiological state, where Treg can regain their ability to efficiently counteract autoimmunity. Areas covered: Here we summarize key findings that led to the development of this novel therapeutic concept and will highlight the key rationales for the clinical translation of low-dose IL-2 therapy in SLE. Expert commentary: The concept of low-dose IL-2 therapy in SLE has evolved from pathophysiological findings and thus can be considered a selective biological treatment strategy in SLE. Preliminary results from phase I/II studies are promising by proving selective Treg expansion and by providing first evidence for the clinical efficacy of low-dose IL-2 therapy in SLE.