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 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 from MPL/lpr mice and SLE patients. The mTOR pathway was assessed using RT2 profiler PCR array and verified by RT-PCR.

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 the different TCR V beta usage of V β 5, 6, 8.1/8.2, 12 in IL-17+ DN T cells while V β 14 and 15 in IL-10+ DN T cells.  Consistently, increase of IL-17+ DN T cells (7.9 ± 0.7% vs 4.6 ± 0.6 %, p=0.01) and reduction of IL-10+ DN T cells (1.5 ± 0.24% vs 4.6 ± 0.6%, P< 0.001) were observed in the peripheral blood from the subjects with SLE compared to healthy subjects. Interestingly, the ratio of IL17+/IL10+ DN T cells displayed a significant positive association with SLEDAI (p = 0.02) but negative association with C3 level (p = 0.01). Additionally, the ratio is found remarkedly higher in lupus patients with proteinuria (4.4 ± 1.2% vs 2.4± 0.4% p= 0.03) and positive anti- dsDNA (3.3± 0.3% vs 1.79 ± 0.2% p= 0.02). Of note, IL17+ DN Tc actively express most mTOR pathway associated genes compared to IL10+ DN Tc.

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, in lupus patients with more severe disease and renal involvement.  The two subsets appear to utilize different TCR repertoire and metabolic enzyme patterns.   We demonstrate that the ratio between the two subsets represents a valid disease biomarker and particularly of 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-2/