Cell-cell cooperation in lymphocyte colony formation: studies in human allogeneic marrow transplantation

The pace of restoration of phytohemagglutinin- (PHA) stimulated lymphocyte colony-forming response was investigated in 50 bone marrow transplant (BMT) recipients (49 allogeneic, 1 syngeneic) studied on 86 occasions. On the majority of occasions (28 of 48), patients studied early (3 to 8 wk) after BMT failed to make detectable lymphocyte colonies, whereas patients studied late (greater than 6 mo) after BMT displayed responses comparable to those of healthy adult volunteers. The sequential study of 10 of the 15 patients with positive lymphocyte colony-forming responses early after BMT revealed that this response is short-lived. The results of recipient donor mixing experiments and experiments involving the addition of the lymphokine interleukin 2 (IL 2) to recipient cells indicated that lymphocytes obtained from unresponsive recipients evaluated early after BMT can be driven to colony formation, and suggest that the major limiting component in such subjects is functional T help.