Epigenetic effect of folic acid (FA) on the gene proximal promoter area and mRNA expression of chicken B cell as antigen presenting cells.

1. This study evaluated and characterised the effect of folic acid (FA) on chromosomal DNA methylation and the epigenetic result on gene expression control mechanisms in chicken B cells as a model of antigen presenting cells. 2. After FA supplementation, the methylation pattern on the proximal promoter area and mRNA expression of toll-like receptor (TLR) 2b, TLR4, B cell receptor (BCR) immunoglobulin (Ig) β and major histocompatibility complex (MHC) II β chain genes in chicken B cells was observed 3. Chicken B cell line (DT40) cultures were incubated with 0, 1.72 or 3.96 mM of FA for 4 and 8 h and samples were taken at specific time points. After 4 h of incubation, cells were challenged with 0, 1 or 10 µg/ml of lipopolysaccharide (LPS) and samples were collected 4 h post-challenge. 4. FA supplementation modified the methylation patterns of the proximal promoter regions of TLR4, Igß, and MHCII ß chain at 4 and 8 hours of incubation; however, the single CpG dinucleotide of TLR2b remained methylated regardless of the treatment. 5. A positive association was found between FA concentration and percentage DNA methylation on the promoter area of Igβ and TLR2b. However, there was a negative association between FA and MHCII β chain. 6. There were downregulatory effects in TLR4, Igß and MHCII ß chain gene expression after 8 h of incubation, nut not at 4 h. Although incubation time did not affect TLR2b gene expression, FA concentration did, whereby it increased TLR2b expression at 1.72 mM FA (P < 0.05). 7. LPS significant downregulated TLR2b expression, while an interaction between FA and LPS concentration affected TLR4 and Igβ gene expression. 8. In conclusion, the results showed that FA can have an immunomodulatory effect on chicken B cells, possibly affecting their ability to both recognise antigens through the TLR and BCR pathways, and to present it the MHCII presentation pathway.