Development of an autoimmune syndrome affecting the skin and internal organs in P-selectin glycoprotein ligand 1 leukocyte receptor-deficient mice.

OBJECTIVE: To define and characterize the progression of the spontaneous autoimmune disease that develops in mice in the absence of the leukocyte adhesion receptor P-selectin glycoprotein ligand 1 (PSGL-1). METHODS: Skin-resident immune cells from PSGL-1-deficient mice and C57BL/6 control mice of different ages were isolated and analyzed by flow cytometry. Biochemical parameters were analyzed in mouse serum and urine, and the presence of serum autoantibodies was investigated. Skin and internal organs were extracted, and their structure was analyzed histologically. RESULTS: Skin-resident innate and adaptive immune cells from PSGL-1(-/-) mice had a proinflammatory phenotype with an imbalanced T effector cell:Treg cell ratio. Sera from PSGL-1(-/-) mice had circulating autoantibodies commonly detected in connective tissue-related human autoimmune diseases. Biochemical and histologic analysis of skin and internal organs revealed skin fibrosis and structural and functional abnormalities in the lungs and kidneys. Furthermore, PSGL-1(-/-) mice exhibited vascular alterations, showing loss of dermal vessels, small vessel medial layer remodeling in the lungs and kidneys, and ischemic processes in the kidney that promote renal infarcts. CONCLUSION: Our study demonstrates that immune system overactivation due to PSGL-1 deficiency triggers an autoimmune syndrome with characteristics similar to systemic sclerosis, including skin fibrosis, vascular alterations, and systemic organ involvement. These results suggest that PSGL-1 expression contributes to the maintenance of the homeostasis of the immune system and could act as a barrier for autoimmunity in mice.

No evidence of association between functional polymorphisms located within IL6R and IL6ST genes and systemic sclerosis.

Systemic sclerosis (SSc) is a complex autoimmune disease which genetic component has not been yet completely understood. IL6 encodes a cytokine with a crucial role in the development of autoimmunity and fibrosis and its actions mainly are controlled by IL-6 receptor (IL-6R). We aimed to investigate whether the functional genetic variants rs8192284 and rs2228044 previously associated with several autoimmune diseases, located within the IL-6 receptor (IL-6R) subunits IL6R and IL6ST genes, respectively, are involved in the susceptibility to SSc and/or its major clinical subphenotypes. A Spanish cohort including 1013 SSc patients and 1375 controls was genotyped using the TaqMan® allelic discrimination technology. SSc patients were subdivided according to the major clinical forms, autoantibody status and presence of fibrotic lung affection. Our data showed no influence of the selected variants in global SSc susceptibility (rs8192284: P=0.67, odds ratios (OR)=0.98; rs2228044: P=0.99, OR=1.00). Similarly, the clinical/autoantibody subphenotype analyses did not yielded significant results. Our data suggest that the analyzed polymorphisms may not play a significant role in the SSc susceptibility.

The autoimmune disease-associated IL2RA locus is involved in the clinical manifestations of systemic sclerosis.

Regulatory T cells (T(regs)) are crucial in the maintenance of the immune tolerance and seem to have an important role in systemic sclerosis (SSc). The interleukin 2 receptor α (IL2RA) is an important T(reg) marker, and polymorphisms of IL2RA gene are associated with a number of autoimmune diseases. Therefore, we aimed to investigate for the first time the association of the IL2RA locus in SSc. For this purpose, a total of 3023 SSc patients and 2735 matched healthy controls, from six European Caucasian cohorts, were genotyped for the IL2RA gene variants rs11594656, rs2104286 and rs12722495 using the TaqMan allelic discrimination technology. The overall meta-analysis reached statistical significance when the three polymorphisms were tested for association with SSc, the limited subtype (lcSSc) and anti-centromere auto-antibodies (ACAs). However, no significant P-values were obtained when the ACA-positive patients were removed from the SSc and lcSSc groups, suggesting that these associations rely on ACA positivity. The strongest association signal with ACA production was detected for rs2104286 (P(FDR)=2.07 × 10(-4), odds ratio=1.30 (1.14-1.47)). The associations of rs11594656 and rs12722495 were lost after conditioning to rs2104286, and allelic combination tests did not evidence a combined effect, indicating that rs2104286 best described the association between IL2RA and ACA presence in SSc.