Background/Purpose: Double Negative (DN) T cells was initially described in the context of autoimmune lymphoproliferative disease, which is caused by defective T cells apoptosis due to mutation of the Fas and Fas-ligand. Subsequently, other autoimmune disorders such as Systemic Lupus Erythematosus (SLE) and Juvenile Idiopathic Arthritis (JIA) have been shown to have elevated DN T cells as well. Although the exact rule of these cells in autoimmunity is not completely clear, the early studies in lupus nephritis showed that DN T cells make a significant amount of IL17 and interferon-gamma promoting the inflammatory status in these patients. Elevated DN T cell have not been documented in a large Juvenile Dermatomyositis (JDM) population. The aim of this study to determine if untreated JDM patients have elevated DN T cells populations.

Methods: Informed consent was obtained and patients were enrolled in the JM Registry at Ann & Robert H. Lurie Children’s Hospital of Chicago (IRB# 2010-14117).  Subjects with JDM who had T and B cell flow cytometry before the initiation of medical therapy were included in this study (IRB# 2012-14858). The years of study ranged between 1991 and 2019.  Patients with overlap syndrome were excluded from the analysis. Double negative T cells were defined as CD3+ CD4- and CD8- T cells by flow cytometry. Elevated DN T cell was defined as DN T cell more than 2.5% of total T cells. We divided the study population into two groups based on their DN T cells (normal vs. elevated DN T cells). We used T-test and chi-square to measure the differences between the two groups in terms of age, gender, duration of untreated disease, disease activity scores (DAS) Childhood Myositis Assessment Score (CMAS), and myositis-specific antibodies (MSA). This study was supported by the CureJM Foundation.

Results: 69 subjects (80% female, 77% white) were included in this study. Subjects’ MSAs were as follows: 51% P155/140+, 7% MJ+, 4% Mi-2+, 4% MDA-5+, 9% multiple MSAs and 23 % MSA negative. 37 out of 69 (54%) of untreated JDM patients had elevated DN T cells (range from 2.6 – 9.6 % of T cells). There was no significant difference between subjects with normal and elevated DN T cells in term of age, gender, duration of untreated disease, MSA, CMAS, or DAS.

Conclusion: 1) More than half of JDM patients have elevated DN T cells, which is consistent with a previously published study in pediatric SLE; 2) The percentage of DN T cells did not correlate with disease activity markers such as CMAS or DAS. 3) Further study is needed to examine the role of these cells in the pathophysiology of JDM.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/double-negative-t-cells-in-juvenile-dermatomyositis/