This mouse study tested whether loss-of-function *Dnmt3a* mutations (introduced by CRISPR-Cas9 or Cd4cre recombination) in CD4+ T cells enhance autoreactive T follicular helper (Tfh) cell responses and joint inflammation, using the KRN+ TCR transgenic transfer model of autoimmune arthritis.
Contrary to the hypothesis, *Dnmt3a* loss-of-function in CD4+ T cells **reduced** Tfh responses, IgG production, and autoantibody levels, and mice receiving mutant autoreactive CD4+ T cells developed significantly attenuated joint inflammation with lower systemic IL-6.
- Entirely preclinical (mouse model); direct translation to human RA is uncertain. - Somatic *DNMT3A* mutations in RA patients occur across multiple hematopoietic lineages, but this study only assessed CD4+ T cell–intrinsic effects. - The KRN+ transfer model may not fully capture the complexity of human seropositive RA.
These findings suggest that *DNMT3A* mutations in CD4+ T cells alone do not explain the increased inflammation seen in RA patients with clonal hematopoiesis — clinicians should consider that other hematopoietic cell types may drive that association. No immediate change in clinical management is indicated pending human studies.
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