Increased T-lymphocyte apoptosis in lupus correlates with disease activity and may be responsible for reduced T-cell frequency: a cross-sectional and longitudinal study

Abstract

Apoptosis of lymphocytes is increased in patients with lupus. This may be pathogenic leading to increased load of autoantigens or may be a bystander effect of immune activation. A major unresolved issue is whether apoptosis is related to disease activity. Also its association with lymphocyte frequencies, anti-nucleosomal antibodies and serum IL 10 levels needs to be explored further. The aims of this study are to measure T- and B-lymphocyte apoptosis in patients with lupus and look at the effect of disease activity in a cross-sectional and longitudinal design and to determine frequency of T and B cells, level of anti-nucleosomal antibodies and serum IL 10 and assess their relationship with apoptosis. This study included 41 patients with SLE and 20 controls. A cutoff value of 4 in systemic lupus erythematosus disease activity index (SLEDAI) was used to separate active from inactive SLE. The frequency and degree of apoptosis of T and B lymphocyte were enumerated by flow cytometry using peripheral blood mononuclear cells (PBMCs) stained with CD3/CD19 and annexin V/PI. The data for T/B cell frequency are represented as % of these cells in the PBMC population, whereas percentage of apoptotic cells is out of total T or B cells. Serum anti-nucleosomal antibodies and IL 10 were assayed using ELISA. A repeat assessment of these parameters was carried out in 11 active patients when they became inactive. We found higher T-lymphocyte apoptosis in patients with SLE versus controls (14.8 +/- 9.2, 7.2 +/- 3.0; P < 0.05) and a lower frequency of T cells (72.7 +/- 12.6, 79.9 +/- 5.8; P < 0.05). T-lymphocyte apoptosis was higher in patients with active disease compared with inactive (18.5 +/- 11.3, 11.6 +/- 5.4; P = 0.05). Further, T-lymphocyte apoptosis directly correlated with SLEDAI (r = 0.37, P < 0.05) and inversely with T-cell frequency (r = -0.29, P < 0.05). Anti-nucleosomal antibodies correlated with SLEDAI but not apoptosis. On longitudinal follow-up, a decline in T-cell apoptosis was seen in patients with SLE, however this was not statistically significant. We confirmed a higher degree of apoptosis in T-lymphocytes in patients with SLE and found a direct correlation of T-cell apoptosis with disease activity. Patients had reduced T-cell frequency, which inversely correlated with T-cell apoptosis and may suggest a cause-effect relationship.

Abnormal CTLA‐4 function in T cells from patients with systemic lupus erythematosus

“…Thus the exaggerated T-cell responses characteristic of SLE could be attributed to CTLA-4 dysfunction. Although CTLA-4 can induce T-cell apoptosis [38] which might therefore be impaired in lupus due to CTLA-4 dysfunction, in fact lupus T cells display an increased rate of apoptosis compared with healthy T-cells [39][40][41][42]. It remains to be determined whether mechanisms independent of CLTA-4 attempt to delete autoreactive T cells through increased apoptosis or their survival is impaired due to prolonged stimulation.…”

Differential Expression of O-Glycans in CD4⁺ T Lymphocytes from Patients with Systemic Lupus Erythematosus

“…Alterations in T cell activation and apoptosis have been described in SLE patients (Vassilopoulos et al 1995;Liossis et al 1998;Dhir et al 2009;Shah et al 2011), both of which seem to be partially regulated by O-glycosylation (Toscano et al 2007;Grigorian et al 2009;Antonopoulos et al 2012). Synthesis of O-glycans starts with the covalent addition of GalNAc to serine or threonine residues, which is catalyzed by a ppGalNAcT, forming the structure known as Tn antigen (Brockhausen et al 2009).…”

“…T cells from SLE patients have shown a reduced activation threshold since T cell receptor (TCR)-triggered downstream signaling rapidly increases tyrosine phosphorylation of proteins and intracellular calcium influx (Vassilopoulos et al 1995;Liossis et al 1998). These cells have also shown an increased susceptibility to apoptosis (Dhir et al 2009;Shah et al 2011), indicating that T cells from SLE patients are activated and regulated abnormally. The regulation of apoptosis seems to depend on the glycosylation pattern of cell surface glycoproteins since distinctive glycosylated structures encourage cell death induced by galectin 1, a glycan-binding protein, in Th1 cells but not in Th2 cells (Toscano et al 2007).…”

Ekspresi CD3 dan CD26 pada Limfosit T sebagai Biomarker Potensial Penyakit Systemic Lupus Erythematosus

“…13 Studi lain melaporkan bahwa limfositopenia pada SLE kemungkinan besar mempunyai korelasi negatif dengan peningkatan laju apoptosis limfosit T. 15 Selain itu, data dalam studi ini menunjukkan bahwa limfositopenia pada pasien SLE juga ditandai dengan penurunan ekspresi CD3 dan CD26 dibanding dengan dengan ekspresi CD3 dan CD26 kontrol pada orang sehat (Gambar 4 dan 5). Selain penurunan ekspresi CD3 dan CD26, beberapa abnormalitas penanda permukaan sel juga ditemukan pada limfosit pasien SLE seperti peningkatan ekspresi CD154 yang merupakan ligan CD40 pada sel B, penurunan sekresi IL-2, dan peningkatan IFN-γ.…”

“…16 Sebagai konsekuensinya, banyak limfosit T mengalami apoptosis dan juga merupakan sumber poten untuk mengaktifkan dan menginduksi antigen presenting cell imatur, meningkatkan kapasitas limfosit T yang autoreaktif, memproduksi sitokin, dan menstimulasi limfosit B yang autoreaktif. 15,16 Selanjutnya, interaksi CD154 dan CD40 akan mengaktifkan limfosit B untuk meningkatkan produksi autoantibodi yang disertai peningkatan sel-sel B dari berbagai tingkat perkembangan.…”