CTLA4 and B-cell chronic lymphocytic leukemia: Chronic lymphocytic leukaemia (CLL) is the most common adult leukaemia in the western world and is associated with significant perturbations of cellular and humoral immunity including an excess of terminally differentiated T cells and elevated expression of exhaustion markers including Program cell Death molecule-1 (PD-1) and Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) (Reviewed in [1]).