Terminal transferase immunofluorescence, enzyme markers and immunological profile of human leukemia-lymphoma cell lines representing different levels of differentiation.

We have examined alterations in terminal deoxynucleotidyl transferase (TdT) immunofluorescence (IF) in MOLT-4 cells during changes in growth conditions. Subsequently, we used cells from 48 human hematopoietic cell lines of different cell lineages and maturation stages to compare the IF and biochemical assays for expression of TdT. In addition, we have attempted to correlate the expression of TdT, adenosine deaminase (ADA), thymidine phosphorylase (TP) and immunological markers with maturation stages in these different cell lines. The results indicate that TdT positive cells remain TdT positive when assayed by either the biochemical or IF tests during growth or early plateau phase, but that cells under poor growth conditions, such as in old cultures, may give a negative TdT IF reaction. Otherwise, biochemical and IF assays for TdT gave comparable results in the 48 cell lines tested, testifying to the reliability of the IF test. Based on the comparisons of the various cell lines studied, it appears that both ADA and TdT decrease progressively as maturation of T cells from Blast I to Blast IV to mature T cells increases. TP was deficient in all T-cell lines compared to normal peripheral blood T cells, which in turn had lower activity compared to normal peripheral blood B cells. Pre-B cells, although indistinguishable from each other by immunological markers and all having low TP and ADA activity, showed heterogeneity, with TdT activity high in some and low in others. All non-T, non-B lines had high TdT activity, but low ADA and TP activity. B- and myelocytic cell lines had low ADA and TdT activity, and showed an increase in TP activity as the maturation of cells increased. These results indicate that the TdT IF test is a reliable procedure for detecting TdT positive cells, and that TdT, ADA and TP could be useful markers for studying the differentiation of human hematopoietic cells.