Effect Of DNA Demethylation On T Cells CD40 Ligand Gene Expression And The Production Of IgG By Autologous B Cells In Systemic Lupus Erythematosus

Objective: To investigate the effect of DNA demethylation on T cells CD40 Ligand (CD40LG) gene expression and the production of IgG by autologous B cells in systemic lupus erythematosus.Methods: Real-time reverse transcription-polymerase chain reaction was used to compare CD40LG expression in CD4+ and CD8+ T cells from SLE patients and CD4+ and CD8+ T cells treated with DNA methyltransferase inhibitors (5-azacytidine and procainamide) and ERK pathway inhibitors (PD98059 and hydralazine) known to decrease DNA methyltransferase expression. The consequences of CD40LG overexpression were tested by coculture of autologous T and B cells with and without anti-CD40LG and measuring IgG production by enzymelinked immunosorbent assay.Results: CD40LG mRNA was overexpressed in female lupus CD4+ T cells or drug-treated CD4+ T cells and possitively correlated with IgG production in lupus CD4+ T cells and drug-treated CD4+ T cells. In addition, we found that T cells from both female and male lupus overstimulated autologous B cells secreting IgG, and this can be reversed with anti-CD40LG in T cells from female lupus patients. Finally, demethylating CD4+ T cells from women but not men stimulated autologous B cells oversecreting IgG, again, anti-CD40LG antibody inhibited overstimulation of IgG synthesis induced by demethylated CD4+ T cells from women but not men.Conclusion: Female lupus CD4+ T cells and demethylating CD4+ T cells overexpress CD40LG. This increased B cell costimulation and subsequent immunoglobulin overproduction may contribute to drug-induced and idiopathic lupus, and demethylation of CD40LG gene on the inactive X may contribute to the striking female predilection of this disease.