The influence of thymus factor X (TFX) and its fraction V on the haemodynamic and haemopoietic functions.

The activity of crude thymus extract (TFX) and its immunologically most active fraction V were assessed comparatively. It was observed that the circulatory activity occurred only when crude thymus extract was applied and that fraction V was almost completely devoid of this activity. On the other hand, the affinity to hemopoietic stem cells is exhibited by the crude TFX and its fraction V. An assumption is put forward that the haemopoietic activity of TFX may be present also in its fractions considered to be immunologically less active.