Assessing the immune cell subset and genetic mutations in palindromic rheumatism negative for rheumatoid factor and anti-citrullinated antibodies

Arthritis Rheumatol. 2022 Jul 12. doi: 10.1002/art.42297. Online ahead of print.


Objectives: The etiology underlying rheumatoid factor and anti-CCP-negative palindromic rheumatism not associated with other rheumatic diseases (seronegative PR) is unclear. We aimed to investigate the immune cells and genes involved.

Methods: This was a single center comparative study of 48 patients with seronegative PR and 48 healthy subjects. Mass cytometry and RNA-sequencing were used to identify the distinct immune subset in blood. Of the 48 patients, 40 had plasma cytokine evaluated by ELISA, 25 had PBMC evaluated by flow cytometry, 21 for real-time PCR, and 3 for whole-exome sequencing (WES).

Results: Immunophenotyping revealed a markedly increased frequency of CD14+CD11b+CD36+ and CD4+CD25-CD69+ cells in active PR patients as compared with controls (both p<0.0001). Gene enrichment analysis of RNA-sequencing data from sorted CD14+CD11b+CD36+/CD4+CD25-CD69+ cell showed involvements in inflammatory/stress response, phagocytosis, and regulation of apoptosis. CXCL16 and IL-10RA upregulations were observed in PR monocytes. Increased levels of PFKFB3, DDIT4, TGF-β1, and downregulation of PDIA6 were found in both monocytes and lymphocytes of active and intercritical PR patients. Plasma S100A8/A9 and IL-1β were elevated in PR. WES revealed novel polygenic mutations in HACL1, KDM5A, RASAL1, HAVCR2, PRDM9, MBOAT4 and JRKL.

Conclusion: In seronegative PR patients, we identified a distinct CD14+CD11b+CD36+ subset, which can induce inflammatory response under stress and exert anti-inflammatory effects after phagocytosis of apoptotic cells, and a CD4+CD25-CD69+ T cell subset with pro- and anti-inflammation properties. Individuals harboring genetic mutations involving epigenetic modification, potentiation and resolution of stress-induced inflammation/ apoptosis, and dysregulated ER stress response could be predisposed to seronegative PR.