Phenotypic and functional similarities between 5‐azacytidine‐treated t cells and a t cell subset in patients with active systemic lupus erythematosus

Abstract

Objective. Antigen-specific CD4+ T cells treated with DNA methylation inhibitors become autoreactive, suggesting a novel mechanism for autoimmunity. To test whether this mechanism might be involved in systemic lupus erythematosus (SLE), phenotypic markers for the autoreactive cells were sought.Methods. Cloned normal T cells were treated with the DNA methylation inhibitor 5-azacytidine (5-azaC) and studied for altered gene expression. T cells from patients with active SLE were then studied for a similar change in gene expression, and cells expressing the marker were tested for autoreactivity.Results. 5-azaC-treated normal T cells had increased CDlla (leukocyte function-associated antigen la) expression relative to other membrane molecules. A T cell subset with similar CDlla expression was found in patients with active SLE. This subset contained cells that spontaneously lysed autologous macrophages, with a specificity similar to that of 5-azaC-treated cells. Conclusion. The model of 5-azaC-induced autoreactivity may have relevance to SLE.Antigen-specific CD4+ T cell clones respond to autologous macrophages (Mgi) without antigen, following treatment with DNA methylation inhibitors such as 5-azacytidine (5-azaC). The response is inhibited by monoclonal antibodies (MAb) against CD3 and class I1 major histocompatibility complex (MHC) determinants, and occurs with autologous but not allogeneic Mgi (1,2), suggesting that the cells are responding to autologous class I1 MHC determinants via a pathway involving the antigedMHC receptor. Similar concentrations of 5-azaC alter gene expression in a wide range of cell types, including T cells (3-3, and the autoreactivity may be caused by changes in the expression of as-yet-unidentified genes involved in T cell activation.5-azaC-induced autoreactivity may have relevance to autoimmunity. Recent experiments have shown that murine T cells can become autoreactive following 5-azaC treatment, responding to and, intriguingly, lysing, syngeneic Mgi. Adoptive transfer of murine 5-azaC-treated cells induces an immune complex glomerulonephritis and anti-DNA antibodies in nonirradiated syngeneic mice (6). These findings suggest a novel model for systemic lupus erythematosus (SLE), in which T cell DNA hypomethylation could alter expression of crucial genes, resulting in T cell autoreactivity, and the autoreactive T cells could then produce a lupus-like illness. Reports that lupusinducing drugs inhibit T cell DNA methylation and induce autoreactivity (7) support this concept. Moreover, recent evidence indicates that T cell DNA methylation is impaired in patients with active SLE (8).

Defective T-cell ERK signaling induces interferon-regulated gene expression and overexpression of methylation-sensitive genes similar to lupus patients

“…The expression of CD11a has previously been reported to be methylation-sensitive in both mouse and human T cells. 15,23,31 To confirm that the expression of CD70 is also methylation-sensitive in mouse T cells, wild-type mouse spleen cells were stimulated with Con-A overnight, and then incubated with or without the DNA methylation inhibitor 5-azacytidine (5 μM) in interleukin 2 (IL-2; 50 U ml −1 ) containing culture media for an additional 72 h. T cells were isolated and the expression of CD70 measured by real-time RT-PCR. We found that CD70 expression increased with 5-azacytidine treatment in wild-type mouse T cells (1.18 ± 0.26 to 5.12 ± 0.84 (mean ± s.e.m.…”

“…14 Hypomethylated, autoreactive CD4+ cells also spontaneously kill autologous macrophages (Mø), causing release of antigenic nucleosomes through mechanisms including demethylation and subsequent overexpression of the PRF1 (perforin) gene. [15][16][17] The hypomethylated cells also overstimulate autologous B-cell antibody production, due to demethylation and overexpression of the genes encoding CD70 (TNFSF7), and CD40L (CD40LG). 18,19 Importantly, procainamide and hydralazine, which cause anti-nuclear antibodies in a majority of people and a lupus-like disease in a subset, are DNA methylation inhibitors.…”

Effective treatment of experimental lupus nephritis by combined administration of anti-CD11a and anti-CD54 antibodies

“…The importance of the CD11a/CD54 interaction in SLE is further emphasized by observations that CD11a and CD54 expression is significantly increased on peripheral blood lymphocytes from patients with SLE [57,58]. Additionally, CD11a expression is relatively increased on T cells from SLE patients, which correlates with disease activity [59].…”

Perforin level in CD4+ T cells from patients with systemic lupus erythematosus

“…T cells from lupus patients may kill autologous monocytes/macrophages, and may thus contribute to both increase of the amount of antigenic apoptotic material and the reduction of its clearance [13,14].…”