TNF and B-cell chronic lymphocytic leukemia: Key elements of the microenvironment are monocyte-derived nurse-like cells (NLCs), mesenchymal stromal cells, T cells, NKT and NK cells, which communicate with CLL cells through a complex network of adhesion molecules, chemokine receptors, tumour necrosis factor (TNF) family members and soluble factors (Figure 1) [15].