Association of specific tyrosine phosphorylation with stages of B-cell differentiation in human lymphoid leukemias.

In vitro protein phosphorylation in various types of human fresh lymphoid leukemic cells (C-ALL, B-CLL, HCL and PCL: B-cell lineage and T-ALL, ATL and T-CLL: T-cell lineage) were studied. In cases of B-CLL and HCL, tyrosine protein kinase (TPK) activity was at least 5-fold higher than that in other cases of B- and T-cell lineages. B-cell leukemic cells at various differentiation stages had different endogenous substrates in tyrosine phosphorylation as well as distinct TPK activity. The P-tyr-containing proteins of 68K, 59K and 56K were detected commonly in all the cases of B-cell lineage. The phosphorylated protein of 32K was present only in cases of PCL. On the other hand, in T-ALL and ATL, the major substrate in tyrosine phosphorylation was 58K. These results suggest that the characterization of in vitro tyrosine phosphorylation provides a new means not only to distinguish T- and B-lymphoid leukemia, but also to differentiate stages of lymphoid development.