Antibodies produced by plasma cells are critical for protection from infection. It has been demonstrated that global epigenetic modification, such as changes in DNA methylation, occurs during differentiation of plasma cells from B cells. However, the precise mechanisms by which DNA methylation controls plasma cell differentiation are not fully understood. We examined the effect of deficiency of DNA demethylases, Tet2 and Tet3, on B-cell activation and plasma cell differentiation, by generating conditional Tet2/3 double-KO (Tet dKO) B cells. We found that Tet dKO B cells failed to differentiate into plasma cells upon immunization with antigens. Tet dKO B cells proliferated normally and were capable of generating cells with IRF4^int, but not with IRF4^hi, the majority of which were CD138⁺ plasma cells. IRF4 overexpression rescued the defect of Tet dKO B cells in plasma cell differentiation, suggesting that Tet2/3-dependent high IRF4 expression is required for plasma cell differentiation. We identified CpG sites in the Irf4 locus that were demethylated specifically in plasma cells and in a Tet2/3-dependent manner. Our results suggest that Tet2/3-dependent demethylation of these CpG sites is dispensable for initial IRF4 expression but is essential for high IRF4 expression which is prerequisite for plasma cell differentiation.

中文翻译：

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通过控制 IRF4 的表达水平，Tet DNA 脱甲基酶是浆细胞分化所必需的。

浆细胞产生的抗体对于防止感染至关重要。已经证明，在浆细胞从 B 细胞分化过程中会发生整体表观遗传修饰，例如 DNA 甲基化的变化。然而，DNA 甲基化控制浆细胞分化的确切机制尚不完全清楚。我们通过产生条件性 Tet2/3 双 KO (Tet dKO) B 细胞，检测了 DNA 去甲基化酶 Tet2 和 Tet3 缺乏对 B 细胞活化和浆细胞分化的影响。我们发现 Tet dKO B 细胞在用抗原免疫后未能分化为浆细胞。Tet dKO B细胞增殖正常，能够产生带有IRF4 ^int的细胞，但不能产生带有IRF4 ^{hi 的}细胞，其中大部分是CD138⁺浆细胞。IRF4 过表达挽救了 Tet dKO B 细胞在浆细胞分化中的缺陷，表明 Tet2/3 依赖性高 IRF4 表达是浆细胞分化所必需的。我们在Irf4基因座中鉴定了 CpG 位点，这些位点在浆细胞中以 Tet2/3 依赖性方式特异性去甲基化。我们的结果表明，这些 CpG 位点的 Tet2/3 依赖性去甲基化对于初始 IRF4 表达是可有可无的，但对于高 IRF4 表达是必不可少的，这是浆细胞分化的先决条件。