CD40 and B-cell chronic lymphocytic leukemia: CD180-negative cases and CD180-positive non-responders are also unresponsive to cumulative anti-CD40 and IL-4 simulation (Porakishvili et al. 2011) or IgM ligation (unpublished observations) and therefore appear to represent a subset of CLL cases with anergic leukemic cells: a phenotype typically associated with an indolent disease course (Apollonio et al. 2013).