Impact of folic acid on regulatory B lymphocytes from patients with systemic lupus erythematosus in vitro.

Background: Epigenetic modifications of genomes are of particular interest as numerous studies indicate the correlation between DNA methylation and the development of systemic lupus. As a major methyl group donor, folic acid is an important participant in this process. The aim of this study is to determine the effect of low or high dose folate co-culturing with peripheral blood mononuclear cells (PBMCs) on the secretion of interleukin (IL)10 from regulatory cells from lupus patients or from healthy volunteers.

Methods: PBMCs from lupus patients and healthy volunteers were isolated and separated CD19+ B cell populations were cultured in the presence of 4 μg/mL or of 16 μg/mL of folic acid and the DNA methylation level as well as the percentages of B lymphocytes were measured. In another experiment, PBMCs were stimulated in vitro for IL10 production with 1 μg/mL recombinant human CD40L and with 2.5 μg/mL unmethylated CpG dinucleotides and cultured in the presence of 4 μg/mL or of 16 μg/mL of folic acid.

Results: Although co-culturing with low or high folic acid concentrations had no effect on the methylation level of B lymphocytes, particular patients showed an increase in the population of CD19+ IL10+ as well as of CD19- IL10+ cells.

Conclusion: The observed increase may be a consequence of additional indirect or direct methylation of DNA in specific loci of the targeted cells. However, further analysis would clarify the exact mechanism of action of folate and would reveal its immunomodulating potential in this autoimmune disease.