Numerous defects affecting downstream signaling proteins in the BCR pathway and mutations in the interleukin 7 (IL-7) receptor are not direct causes of CLL; however, such factors predispose cells to develop into CLL cells, and they also influence the development of B and T cell malignancies and severe immunodeficiencies (11, 12). This evidence concerns the gene BCR and B-cell chronic lymphocytic leukemia.