A relative loss of naïve CD4+ T-cells and an accumulation of antigen-experienced CD4+ T-cells, as well as a higher expression of the early activation markers CD69 and PD-1, was noted [10], suggesting that this model is a useful tool to investigate the role of CD4+ T-cells in CLL. The gene discussed is PDCD1; the disease is B-cell chronic lymphocytic leukemia.