IL6 and plasma cell myeloma: The effect of high levels of IL-6 may be due to the competition of significant amounts of cytokine with tocilizumab for binding sites (IL-6R) on the membranes of target cells, i.e., immunocompetent cells and hepatocytes, but not for soluble forms of the receptor, which is confirmed in studies with IL-6-dependent myeloma cell line and recombinant BaF/IL-6R (33).