Determination of the probability of self-renewal in haemopoietic stem cells: a puzzle.

This paper calls attention to anomalous behaviour of the spleen colony forming cell system, when quantitative measurements of the self-renewal probability of the CFU-S are attempted.

Tissues and stem cells.

This brief overview of the different cell populations types contained in the various tissues of the adult organisms, with special reference to cell population hierarchies and kinetic patterns, indicates that not all cell populations have--nor do they need--stem cells; in those which have, the stem cells usually represent a minority subpopulation.

Which are the leukaemic cells?

Two features are known about acute myeloid leukaemia in man: (1) the long time-scale from identifiable leukaemogenic stimulus and onset of the clinical disease and (2) the successful induction and duration of long clinical remission. These indicate three probabilities: First, that the target cell for leukaemogenetic insult (in AML) is the pluripotent stem cell; second, that the leukaemic stem line is a small minority population within the total leukaemic cell mass; third, when the leukaemic stem line is not greatly exceeding the normal stem cell numbers, its proliferation may be still under partial control.