Peroxisomal ABCD1 deficiency in mice drives Th1 bias through 25-HC-LXR signaling in CD4⁺ T cells

X-linked adrenoleukodystrophy (X-ALD) is driven by ABCD1 dysfunction, causing very-long-chain fatty acid (VLCFA) accumulation and cerebral inflammation, yet the role of T cells in X-ALD remains unclear. Here, we show that Abcd1-deficient CD4⁺ T cells exhibit a strong Th1 bias, producing more IFN-γ and less IL-10 under antigen-specific immunization in vivo and Th1-polarizing conditions in vitro. Transcriptional profiling revealed early induction of Ifng and Tbx21 (T-bet) and late repression of Prdm1 (Blimp-1), indicating Blimp-1-dependent derepression of IFN-γ and reduced IL-10. Mechanistically, liver X receptor (LXR) signaling was markedly amplified, evidenced by upregulation of Abca1, Srebf1, and the oxysterol 25-hydroxycholesterol (25-HC), driven by increased Ch25h. Pharmacological modulation validated this axis: the LXR antagonist SR9238 restored Blimp-1 and IL-10 while reducing IFN-γ, whereas the LXR agonist T0901317 and exogenous 25-HC recapitulated the Abcd1-deficient phenotype. Thus, 25-HC-LXR signaling suppresses Blimp-1, enforcing Th1 polarization in Abcd1-deficient CD4⁺ T cells. These findings define an immunometabolic link between peroxisomal lipid metabolism and T cell differentiation and highlight the 25-HC-LXR-Blimp-1 axis as a mechanistic link regulating CD4⁺ T-cell polarization, with potential relevance to X-ALD-associated neuroinflammation.