Research article

Low frequency of CD4⁺CD25⁺ Treg in SLE patients: a heritable trait associated with CTLA4 and TGFβ gene variants

Marta Barreto¹, Ricardo C Ferreira¹, Lara Lourenço¹, Maria F Moraes-Fontes¹, Eugénia Santos^2,3, Miguel Alves³, Cláudia Carvalho⁴, Berta Martins^4,5, Rita Andreia², João F Viana², Carlos Vasconcelos², Luísa Mota-Vieira⁶, Carlos Ferreira^2,3, Jocelyne Demengeot¹ and Astrid M Vicente^1,7*

• * Corresponding author: Astrid M Vicente avicente@igc.gulbenkian.pt

Author Affiliations

¹ Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6 2780-156 Oeiras, Portugal

² Associação dos Doentes com Lupus, Av. Defensores de Chaves 27, 4°D 1000-110 Lisboa, Portugal

³ Clínica Universitária de Medicina II, Hospital de Santa Maria, Avenida Professor Egas Moniz 1649-035 Lisboa, Portugal

⁴ Instituto de Ciências Biomédicas Abel Salazar, Largo Prof. Abel Salazar 2, 4099-003 Porto, Portugal

⁵ Instituto Nacional de Saúde Dr. Ricardo Jorge, Largo 1° de Dezembro, 4049-019 Porto, Portugal

⁶ Hospital Divino Espírito Santo de Ponta Delgada, EPE, Avenida D. Manuel I 9500-370 Ponta Delgada, Azores, Portugal

⁷ Instituto Nacional de Saúde Dr. Ricardo Jorge, Av. Padre Cruz, 1600-560 Lisboa, Portugal

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BMC Immunology 2009, 10:5 doi:10.1186/1471-2172-10-5

Published: 27 January 2009

Abstract

Background

CD4⁺CD25⁺ regulatory T cells play an essential role in maintaining immune homeostasis and preventing autoimmunity. Therefore, defects in Treg development, maintenance or function have been associated with several human autoimmune diseases including Systemic Lupus Erythematosus (SLE), a systemic autoimmune disease characterized by loss of tolerance to nuclear components and significantly more frequent in females.

Results

To investigate the involvement of Treg in SLE pathogenesis, we determined the frequency of CD4⁺CD25⁺CD45RO⁺ T cells, which encompass the majority of Treg activity, in the PBMC of 148 SLE patients (76 patients were part of 54 families), 166 relatives and 117 controls. SLE patients and their relatives were recruited in several Portuguese hospitals and through the Portuguese Lupus Association. Control individuals were blood donors recruited from several regional blood donor centers. Treg frequency was significantly lower in SLE patients than healthy controls (z = -6.161, P < 0.00001) and intermediate in the relatives' group. Remarkably, this T cell subset was also lower in females, most strikingly in the control population (z = 4.121, P < 0.001). We further ascertained that the decreased frequency of Treg in SLE patients resulted from the specific reduction of bona fide FOXP3⁺CD4⁺CD25⁺ Treg. Treg frequency was negatively correlated with SLE activity index (SLEDAI) and titers of serum anti-dsDNA antibodies. Both Treg frequency and disease activity were modulated by IVIg treatment in a documented SLE case. The segregation of Treg frequency within the SLE families was indicative of a genetic trait. Candidate gene analysis revealed that specific variants of CTLA4 and TGFβ were associated with the decreased frequency of Treg in PBMC, while FOXP3 gene variants were associated with affection status, but not with Treg frequency.

Conclusion

SLE patients have impaired Treg production or maintenance, a trait strongly associated with SLE disease activity and autoantibody titers, and possibly resulting from the inability to convert FOXP3⁺CD25^- into FOXP3⁺CD25⁺ T cells. Treg frequency is highly heritable within SLE families, with specific variants of the CTLA4 and TGFβ genes contributing to this trait, while FOXP3 contributes to SLE through mechanisms not involving a modulation of Treg frequency. These findings establish that the genetic components in SLE pathogenesis include genes related to Treg generation or maintenance.