CTLA4 and plasma cell myeloma: The virtual absence of FOXP3 and CTLA4 expression in myeloma cells and the linear correlation of CTLA4 gene expression with that of BM-infiltrating Tregs by flow cytometry led us to believe that most of the expression of Treg-related genes in myeloma BM aspirates might be due to the presence of the immunosuppressive CD4+ T cell subpopulation in tumor microenvironment.