CTLA4 and systemic lupus erythematosus: The specific polymorphisms associated with CD4+CD25+CD45RO+ cell frequency were not correlated with CTLA-4 and TGF-β mRNA expression level variation; expression levels in turn were not associated with cell variation or with disease status, indicating that a functional defect in these genes, rather than changes in expression levels, contributes to the observed CD4+CD25+CD45RO+ T cell phenotype in SLE patients.