Evidence for a pathogenic role of extrafollicular, IL-10-producing CCR6+B helper T cells in systemic lupus erythematosus.

Interleukin 10 (IL-10) is an antiinflammatory cytokine, but also promotes B cell responses and plays a pathogenic role in systemic lupus erythematosus (SLE). CD4+CCR6+IL-7R+T cells from human tonsils produced IL-10 following stimulation by naïve B cells, which promoted B cell immunoglobulin G (IgG) production. These tonsillar CCR6+B helper T cells were phenotypically distinct from follicular helper T (TFH) cells and lacked BCL6 expression. In peripheral blood, a CCR6+T cell population with similar characteristics was identified, which lacked Th17- and TFH-associated gene signatures and differentiation-associated surface markers. CD4+CCR6+T cells expressing IL-10, but not IL-17, were also detectable in the spleens of cytokine reporter mice. They provided help for IgG production in vivo, and expanded systemically in pristane-induced lupus-like disease. In SLE patients, CD4+CCR6+IL-7R+T cells were associated with the presence of pathogenic anti-dsDNA (double-stranded DNA) antibodies, and provided spontaneous help for autoantibody production ex vivo. Strikingly, IL-10-producing CCR6+T cells were highly abundant in lymph nodes of SLE patients, and colocalized with B cells at the margins of follicles. In conclusion, we identified a previously uncharacterized population of extrafollicular B helper T cells, which produced IL-10 and could play a prominent pathogenic role in SLE.

Updating on the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a multi-organ autoimmune disease whose pathogenesis is multifactorial lying on genetic, environmental factors and on abnormalities of both the innate and the adaptive immune system. The induction, maintenance and progression of the disease are a multi-step process that may take long time eventually leading to tissue injury. Several genes have been associated to SLE susceptibility; each of them displaying a small effect suggesting the need of an association. However, the gene-gene and gene-environment interactions are still matter of research. Environmental factors, both external such as physical and infectious agents and internal such as gender and hormonal profile, may influence the disease manifestation. SLE is characterized by a complex array of immune abnormalities affecting both the innate and the adaptive immunity. All these processes play a role in the defective clearance of chromatin material that is overexposed to the afferent limb of the immune system leading to an autoimmune response facilitated by defective regulatory mechanisms. The production of a wide panel of autoantibodies represents the ultimate events responsible for tissue aggression. Finally, tissue damage is influenced by the presence of local factors responsible for the final aggressivity of the lesions and of the clinical manifestations.