Nonspecific increase of αβTCR⁺ double-negative T cells in pediatric rheumatic diseases

Background: An increased number of double-negative T (DNT) cells expressing the αβ T cell receptor (αβ⁺DNT cells) is one of the diagnostic criteria for autoimmune lymphoproliferative syndrome (ALPS). Moreover, these cells are expanded in a widely used murine model for lupus. However, the homeostasis of αβ⁺DNT cells remains inadequately investigated in rheumatic disorders, especially in pediatric patients. Methods: In this cross-sectional, prospective, and observational study, children with rheumatic disorders and healthy controls were recruited to analyze the quantity and characteristics of circulating DNT cells using flow cytometry. Results: Overall, the two study groups did not differ in their total DNT cell pool in the bloodstream. However, the number of αβ⁺DNT cells was significantly higher in rheumatic children than that in the controls, whereas the γδ⁺DNT cells remained similar. This expansion in the circulating pool of αβ⁺DNT cells was comparable across different rheumatic diseases, all showing significant differences from the controls in this regard. Moreover, no significant correlation was found between αβ⁺DNT cell numbers and disease activity. Conclusions: These preliminary results indicate that circulating αβ⁺DNT cells are significantly expanded in children with rheumatic disorders; however, this finding appears to be a nonspecific (disease-unrelated) marker of autoimmunity. Further and larger studies are necessary to better investigate and define the role of DNT cells in pediatric rheumatic diseases.