CD4 and renal cell carcinoma: Given reports that Type-1 CD4+ T cells are subjected to chronic antigen-stimulation making them differentially (vs. Type-2 or Treg) sensitive to activation-induced cell death (AICD) via an apoptotic mechanism (21), we hypothesized that TAA-specific CD4+ T cells freshly isolated from the peripheral blood of melanoma or renal cell carcinoma (RCC) patients with active disease (AD) would have a higher likelihood of exhibiting a pro-apoptotic phenotype.