This suggests that the probability of class-switching to any isotype is dependent on the nature of the B-cell clone (i.e., malignant versus healthy) and despite the different genetics, signaling, and microenvironment between individual CLL cases, there is a consistent and significant bias in the fate of malignant B-cell clones to IgA1/2 isotypes. This evidence concerns the gene IGHA1 and B-cell chronic lymphocytic leukemia.