However, in the majority of B cell malignancies, including CLL, the isotype of BCR-associated surface immunoglobulin (sIg) is restricted to IgM and somatic hypermutation may not have been occurred yet at the time of malignant transformation, marking leukemic cells with a less anergic profile and a more aggressive behavior. Here, CD40LG is linked to B-cell chronic lymphocytic leukemia.