Terminal transferase positive cells in the human bone marrow and thymus.

Abstract

The original impetus for this study has been the urge for a better understanding of human leukaemias, and the need for developing sensitive single cell assays to recognize individual leukaemic cells. In order to achieve this aim, more had to be learned about the normal human cell types (so-called ‘normal equivalent’ cells) from which the leukaemias originate (1). Terminal deoxynucleotidyl transferase (TdT) is one of the most useful markers in this respect for the following reasons. First, TdT is present in the vast majority of acute lymphoblastic leukaemias (ALL, ref.2,3); thus anti-TdT antibody, developed by Bollum (4), can be used as a “pointer” to specifically recognize leukaemic cells (e.g. residual malignant cells in treated patients) and their normal counterparts. Second, being a nuclear enzyme it is convenient to use anti-TdT antibody in combinations with various antisera reacting with membrane antigens. With the help of these combined assays a surprisingly extensive phenotypic profiles can be assembled about the TdT positive cells in the bone marrow (BM)and thymus. These studies represent the overture for studies which will isolate these human cells and further analyse their functional characteristics and development potential in vitro.