FOXP3 and systemic lupus erythematosus: Taken together these results indicate that CTLA4 and TGFβ gene variants contribute to the determination of CD4+CD25+CD45RO+ T cell frequency in PBMC, independently of disease activity, while the involvement of FOXP3 gene variants in SLE is likely not mediated by CD4+CD25+CD45RO+ T cell frequency.