Given that H2O2 is a known inhibitor of phosphatase activity, and that phosphatase activation is a physiological regulator of proximal BCR signaling activities [5], [14]–[17], [21]–[23], these data suggest that deregulation of phosphatase activity could explain some of the differences observed between CLL and healthy B cell signaling responses. This evidence concerns the gene BCR and B-cell chronic lymphocytic leukemia.