In some T cells progressing to senescence, apoptotic markers have been found, such as low expression of the anti-apoptotic gene, B-Cell CLL/Lymphoma 2 (Bcl-2), and up-regulation of cell death markers, such as Tumor Necrosis Factor Receptor Superfamily Member 6 (CD95), which lead to p53-mediated cell death [38]. This evidence concerns the gene FAS and B-cell chronic lymphocytic leukemia.