In addition, we show increased autophosphorylation of Lyn at Y396 in the catalytic domain that is required for full catalytic activity of this kinase in IgG M-CLL compared with IgM U-CLL or IgM M-CLL, but with no differences in phosphorylation of the inhibitory tyrosine (Y507). The gene discussed is LYN; the disease is B-cell chronic lymphocytic leukemia.