Measurement of natural (CD4+CD25high) and inducible (CD4+IL-10+) regulatory T cells in patients with systemic lupus erythematosus

[Regulatory T cells and systemic autoimmune diseases: systemic lupus erythematosus, rheumatoid arthritis, primary Sjögren's syndrome]

Regulatory/suppressor T cells (Tregs) maintain immunologic homeostasis and prevent autoimmunity. They are the guardians of dominant tolerance. Recent research reveals quantitative and/or functional defect of Tregs in systemic autoimmune diseases. In this article, past and recent studies of Tregs in human systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and primary Sjögren's syndrome (pGSS) are reviewed. Most studies report that Tregs are decreased in peripheral blood of subjects with active SLE. A population of CD4+CD25-Foxp3+ is specifically described in SLE. Tregs functions are still discussed. Tregs counts in peripheral blood of RA patients vary across studies. Enrichment of synovial fluid in Tregs contrasts with inflammation. Tregs suppressive effects are altered in vivo in RA secondary to proinflammatory cytokines environment and resistance of effector T cells to Tregs. In pGSS, the conflicting place of Tregs in the balance prevention of autoimmunity/antitumor immunity is unspecified. Immunosuppressive treatments, like corticosteroids and anti-TNF, modulate Tregs cells population. There is increasing interest in the use of Tregs as a biological therapy to preserve and restore tolerance to self-antigen. However, difficulties to characterize these lymphocytes and controversies in the results of studies refrain their use in current clinical practice.

Cells with regulatory function of the innate and adaptive immune system in primary Sjögren's syndrome

The aim of the present study was to describe subsets of cells with regulatory properties in primary Sjögren's syndrome (pSS), and to correlate these cell populations with clinical symptoms. Among the 32 investigated patients, 23 had extraglandular manifestations (EGMs), while nine had only glandular symptoms. Twenty healthy individuals served as controls. The percentages of natural killer (NK), natural killer T cells (NK T), interleukin (IL)-10 producing T regulatory type 1 (Tr1) cells and CD4(+)CD25(+) regulatory T cells (T(reg)) cells were determined by flow cytometry and serum cytokine levels of IL-4, IL-6, IL-10, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma were evaluated by enzyme-linked immunosorbent assay (ELISA). Functional tests were carried out to assess the suppressor properties of T(reg) cells in patients and controls. Peripheral NK, NK T and Tr1 cell percentages were elevated in pSS, while CD4(+)CD25(+) T(reg) cells showed reduced frequencies in patients compared to controls. In pSS, elevated percentages of NK T, Tr1 and CD4(+)CD25(+) T(reg) cells were observed in patients with EGMs, when compared to patients with sicca symptoms only. CD4(+)CD25(+) T(reg) cell percentages showed a negative correlation with sialometry values. The in vitro functional assay demonstrated lower suppression activity of CD4(+)CD25(+) T(reg) cells in patients compared to controls. Serum IL-6 and TNF-alpha levels were elevated, while IL-10 was decreased in patients compared to controls. Negative correlation was found between IL-10 levels and the percentages of Tr1 cells. Changes in the investigated subsets of regulatory cells in pSS may contribute to the development and progression of the disease.

Identification of regulatory T cells in systemic lupus erythematosus

The concept that regulatory T cells (Treg) play a key role in both development and maintenance of autoimmune response in rheumatic diseases is well accepted. In recent years, several studies analyzed Treg cell phenotype and function in systemic lupus erythematosus (SLE), the prototypical systemic autoimmune disorder in humans. Although qualitative and/or quantitative abnormalities of Treg cells have been shown, data are often conflicting. This may depend on the selection of patients with different degrees of disease activity or on immunosuppressive treatments that can alter Treg cell findings. Among several proposed surface or intracellular Treg cell markers, CD25 at high level of expression and the transcription factor Foxp3 are the two most investigated in SLE. Despite the glucocorticoid-induced TNF receptor-related protein (GITR) represents a reliable phenotypic marker of murine Treg cells, little is known about its role in humans, in particular in the course of systemic autoimmune disorders. Preliminary data seems to suggest that this marker may represent a good tool to identify cell populations included within Treg cell subsets.

Regulatory T cells in systemic lupus erythematosus: past, present and future

Regulatory/suppressor T cells (Tregs) maintain immunologic homeo-stasis and prevent autoimmunity. In this article, past studies and recent studies of Tregs in mouse models for lupus and of human systemic lupus erythematosus are reviewed concentrating on CD4⁺CD25⁺Foxp3⁺ Tregs. These cells consist of thymus-derived, natural Tregs and peripherally induced Tregs that are similar phenotypically and functionally. These Tregs are decreased in young lupus-prone mice, but are present in normal numbers in mice with established disease. In humans, most workers report CD4⁺Tregs are decreased in subjects with active systemic lupus erythematosus, but the cells increase with treatment and clinical improvement. The role of immunogenic and tolerogenic dendritic cells in controlling Tregs is discussed, along with new strategies to normalize Treg function in systemic lupus erythematosus.

CD4(+)CD25 (+) regulatory T cells in human lupus erythematosus

Natural CD4(+)CD25(+) regulatory T cells (T(reg)) show a potent immunosuppressive function and contribute to immunologic self-tolerance by suppressing potentially auto-reactive T cells. Depletion of these cells leads to the induction of severe autoimmune diseases in animal models; more recently, several studies have also reported an impairment of T(reg) number and/or function in various human autoimmune diseases. For example, aberrant numbers of circulating CD4(+)CD25(+) T(reg) have been seen in patients with type I diabetes, mycosis fungoides, graft-versus-host-reaction, and rheumatoid arthritis. Moreover, increased numbers of functionally active CD4(+)CD25(+) T(reg) have been detected in the synovial fluid of patients with rheumatoid arthritis. In systemic lupus erythematosus (SLE), conflicting data on the role of CD4(+)CD25(+) T(reg) in human autoimmune diseases have been presented in the literature. Decreased numbers of peripheral blood T(reg) have been reported by most studies on SLE patients with active disease, but non-impaired or even increased CD4(+)CD25(+) T(reg) numbers have also been described. In addition, both deficient and normal suppressive capacity of isolated T(reg) have been observed in SLE. Analysis of CD4(+)FoxP3(+) T(reg) in skin lesions of patients with a primarily cutaneous manifestation of the disease showed a significant reduction in cell numbers as compared to other inflammatory skin diseases, suggesting the importance of analyzing T(reg) numbers in the affected tissue. In this review, we discuss the role of CD4(+)CD25(+) T(reg) in autoimmunity and recent published data on SLE. Furthermore, we highlight the need for additional studies that address specific gaps of knowledge regarding the pathophysiological mechanisms as well as the identification of future therapeutic strategies for autoimmune diseases.

NK and NKT cell dynamics after rituximab therapy for systemic lupus erythematosus and rheumatoid arthritis

Biomarkers of clinical response to rituximab (RTX) therapy and early predictors of outcome are still under investigation. We report a flow cytometric immunophenotyping analysis from peripheral blood leukocyte subpopulations of two patients with systemic lupus erythematosus (SLE) associated thrombocytopenia and one patient with rheumatoid arthritis (RA), before and after 6 weeks of treatment with RTX. Our results show a reduced population of CD19(+) expressing cells (B cells) after RTX treatment in all three patients. Increased frequency of peripheral regulatory CD4(+)CD25(high) T cell subset and the CD3(-)CD16(-)CD56(bright) NK cell subset after RTX therapy were also observed in all patients, the latter being more pronounced in the SLE patient with sustained clinical response. In addition, an increased population of NKT cell subsets was observed in the patients with clinical response. This is the first evaluation of NK and NKT cells as biomarkers of clinical response after rituximab therapy in rheumatic diseases.