Figure 4. Acetate and butyrate promote B cell IgG production and plasma B cell differentiation related genes through interaction with DCs.

Splenic naïve IgD⁺ B cells were cultured with 1 mM acetate (C2) or 0.5 mM butyrate (C4) for 5 days in the presence of 5 μg/ml anti-μ plus 5 μg/ml CD40L (A), or 1 μg/ml LPS (B), and IgG production in supernatants was determined by ELISA. (C) Splenic naïve IgD⁺ B cells were cultured with BMDCs in the presence of C2 or C4 for 5 days, and IgG levels in supernatants were analyzed by ELISA. (D) BMDCs were treated with or without C2 (1 mM) or C4 (0.5 mM) for 6 hrs, and then cultured with splenic naïve IgD⁺ B cells for 5 days. IgG levels in supernatants were analyzed using ELISA. (E) Splenic naïve IgD⁺ B cells were cultured with 5 μg/ml anti-μ plus 5 μg/ml CD40L for 5 days in the conditional medium (CM) from BMDCs treated with or without C2 (1 mM) or C4 (0.5 mM). IgG production in supernatants was measured using ELISA. (F-H) Naïve IgD⁺ B cells were cultured in different CM in the presence of 5 μg/ml anti-μ plus 5 μg/ml CD40L for 2 days. The expression of IRF4 (F), Blimp1 (G), and XBP1(H) was determined by qRT-PCR and normalized against GAPDH. (I-K) Groups (n = 4–5) of WT mice were immunized with 100 μg OVA and 10 μg CT on day 0 and day 14 by gavage. The mice were fed with or without a mixture of 200 mM acetate (C2) and butyrate (C4) in drinking water for 28 days. Splenic B220⁺ B cells were isolated from these mice on day 28, and the expression of IRF4 (I), Blimp1 (J), and XBP1 (K) was determined by qRT-PCR and normalized against GAPDH. One representative of three independent experiments was shown. The data were expressed as mean ± s.e.m. *p < 0.05, **p < 0.01, *** p < 0.001.