Background/Purpose: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and associated with a wide range of clinical manifestations. Recent case-control association study suggests that polymorphisms in the early growth response gene-2 (EGR2), a zinc-finger transcription factor, influence SLE susceptibility in humans. In line with the observation, T-cell-specific Egr-2-deficient mice show lupus-like autoimmune disease. We previously described CD4⁺CD25^–Foxp3^– regulatory T cells (Treg) that characteristically express both lymphocyte activation gene 3 (LAG3, CD223) and Egr2 (hereinafter referred to as ‘LAG3⁺ Treg’). Therefore, we have examined whether LAG3⁺ Treg suppress the development of follicular helper T cell (T_FH) and germinal center B cell (GCB), antibody production, and disease progression in lupus-prone MRL-Fas^lpr/lpr (MRL/lpr) mice.

Methods: B cells from C57BL/6 (B6) mice and helper T (Th) cells from OT-II mice were injected i.v. into Rag1KO mice in combination with or without LAG3⁺ Treg from B6, Egr2 conditional knockout (CKO) (Egr2^fl/fl CD4-Cre⁺), or Fas-mutated B6/lpr mice. Mice were subsequently immunized with NP-OVA/alum 24 hr after the cell transfer. Mice were re-immunized with NP-OVA/alum 14 days after the first immunization. Serum anti-NP antibody levels were analyzed by ELISA, and splenocytes were analyzed by FACS 7 days after the re-immunization. To examine the therapeutic effects of LAG3⁺ Treg in lupus-prone mice, 8-week-old MRL/lpr mice were randomly assigned to specific treatment groups. Ten-week-old MRL/lpr mice in the treatment group were injected i.v. with LAG3⁺ Treg, CD4⁺CD25⁺Treg, or naïve T cells obtained from MRL/+ mice. Mice were sacrificed at 18 weeks of age to examine pathological alterations. Anti-ds DNA antibodies were measured by ELISA.

Results: Transfer of LAG3⁺ Treg from wild type (WT) mice, but not Egr2 CKO or B6/lpr mice, significantly suppressed NP-specific antibody responses and the development of GCB and T_FH in Rag1KO mice transferred with B cells and OT-II Th cells. Interestingly, LAG3⁺ Treg produce high amounts of transforming growth factor-β3 (TGF-β3) in an Egr2- and Fas-dependent manner. Treatment with a TGF-β3 or FasL blocking antibody cancelled the suppressive activity of WT LAG3⁺ Treg. Adoptive transfer of LAG3⁺ Treg from control MRL/+ mice significantly suppressed the progression of nephritis and autoantibody production in MRL/lpr mice. In contrast, CD4⁺CD25⁺ Treg and naïve T cells from MRL/+ mice exhibited no significant therapeutic effect upon transfer to MRL/lpr mice. TGF-β3-blockade also abrogated the therapeutic effects of MRL/+ LAG3⁺ Treg in MRL/lpr mice.

Conclusion: These results clarified the molecular basis underlying TGF-β3-producing LAG3⁺ Treg-mediated B cell regulation, which indicated that LAG3⁺ Treg may be a suitable target for immune manipulation in autoantibody-mediated autoimmune diseases, including SLE.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tgf-%ce%b23-producing-cd4cd25lag3-regulatory-t-cells-control-b-cell-responses/