| Abstract |
Acute lymphoblastic leukaemia (ALL) has been shown to be a very
heterogeneous malignant disease in which the majority of cases cannot be
clearly related to either the T or B cell ontogeny pathway. A small
percentage of cases, however, have been clearly shown by numerous
immunological methods to be of T cell origin. This group is in itself a
heterogeneous one with the malignant cells showing early, late or
intermediate differentiation phenotypes. One way to explore these
differences in differentiation states is to establish and characterize
various cell lines from the T-ALL patients and to compare these lines with
normal cells of the T lineage. In the normal T cell differentiation
pathway, the stem cell originates in the bone marrow, migrates to the
thymus (where it is referred to as the prothymocyte) and under thymic
microenvironment differentiates into the cortical thymocyte. Upon further
maturation the thymocyte is exported into the peripheral blood as a mature
T cell. The human prothymocyte has recently been characterized and shown
to compose only a small proportion of the postnatal thymocytes. In
contrast to the cortical thymocytes, the prothymocytes are large cells
with mitotic activity. They do not form E rosettes, do not exhibit natural
attachment (NA) and are highly sensitive to hydrocortisone (HC) induced
cytolysis. The cortical thymocytes do form E rosettes, do express NA and
are HC resistant. In this study, we have characterized a cell line Be13
originating in a patient with T-ALL. By use of the above-mentioned
markers, this line was shown to express a phenotype intermediate to the
prothymocyte and cortical thymocyte. Recent works have shown that the
phorbol esters can act as inducers of certain human leukaemic lines. It
was of interest, therefore, to see whether the Be13 line could be
similarly induced to a more mature differentiation stage along the T cell
lineage.
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