CD40 and B-cell chronic lymphocytic leukemia: Unlike primary CLL cells, CD40- or TLR9-ligated CLL cells, or CpG/IL-21 treated CLL cells, GIFT4-CLL cells robustly up-regulate the expression of co-stimulatory molecules CD40, CD80 and CD86 and adhesion molecule CD54, which are likely essential surface factors for GIFT4-CLL cells functioning as APC to interact with T cells and prime T cell responses.