Background/Purpose: We have previously shown that DN T cells are expanded in both lupus-prone mice and patients with SLE and we have demonstrated that this population is an essential component of the immunopathogenesis of the disease. It still remains unknown whether the DN T cell pool consists of functionally heterogeneous subpopulations. In this study we ask whether DN T cells comprise distinct functional subsets.

Methods: Flow cytometry analysis was applied for the expression of cytokines, chemokine receptors, and T cell receptor (TCR) repertoire etc. IL-17-GFP B6 mice were crossed to MPL/lpr mice for 8 generations to generate IL-17-GFP MPL/lpr mice which were used to track IL-17⁺ DN T cells in vivo and sort IL-17⁺ DN T cells ex vivo. Cytokine capture assay was applied for ex vivo isolation of either IL-17⁺ or IL-10⁺ DN T cells. Metabolism-associated gene expression was quantified by RT-qPCR. Peripheral blood T cells from either healthy subjects or patients with SLE were assessed by flow cytometry analysis.

Results: Two distinct DN T populations were identified in both mice and humans based on the expression of two cytokines, IL-17 and IL-10. As expected, IL-17⁺ DN T cells were significantly increased in aging MRL/lpr mice (20 wks old) compared to either age matched control MRL/mpj mice or young MRL/lpr mice (12 wks old), a finding which is consistent with our previous report that DN T cells contribute to lupus pathogenesis by producing IL-17. Interestingly, the numbers of IL-10⁺ DN T cells in aging (20 wks old) mice were reduced compared to young (12 wks old) MRL/lpr mice. Flow cytometry analysis revealed that the predominant chemokine receptors expressed on IL-17⁺ and IL-10⁺ DN T cells were different. Higher levels of CCR6 expression were observed only on IL-17⁺ DN T cells and especially in those infiltrating the kidneys (64±11.4% in kidneys vs 19.3 ± 5.6% in spleens) but CCR4 expression was restricted on IL-10⁺ DN T cells. Furthermore, different TCR V beta repertoire usage (V β 5, 6, 8.1/8.2, 12) was observed in IL-17⁺ DN T cells while V β 14 and 15 were noted on IL-10⁺ DN T cells. Finally, different expression levels of metabolic genes were recorded between IL-17⁺ vs IL-10⁺ DN T cells. Consistently, increased percentage of IL-17⁺ DN T cells (7.0 ± 5.4% vs 4.1 ± 2.6 %) and reduced IL-10⁺ DN T cells (0.49 ± 0.65% vs 7.5 ± 1.6%) were observed in the peripheral blood from the subjects with SLE compared to healthy subjects.

Conclusion: We present evidence that two distinct subsets exist within the DN T cell population in lupus prone mice and patients with SLE. The ratio of IL-17⁺/10⁺ DN T cells increases as the disease progresses in MRL/lpr mice. The two subsets appear to utilize different TCR repertoire and express different cytokine receptors and metabolic enzyme patterns. We propose that the ratio between the two subsets represents a valid disease biomarker and particularly of impeding kidney involvement.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/identification-of-il-17-and-il-10-tcr%ce%b1%ce%b2-cd4-cd8-double-negative-dn-t-cell-subsets-in-lupus-prone-mice-and-patients-with-sle-and-their-significance-in-predicting-renal-involvement/