Role of interleukin-1 in 4-hydroperoxycyclophosphamide toxicity to bone marrow progenitor cells: a review

We have demonstrated that in vitro preincubation with IL-1 or TNFa for 20 hours can protect human hematopoietic progenitors from lethal doses of 4-HC. On the other hand, preincubation with IL-6 or IL-3, in a similar fashion, did not provide any protection but in fact demonstrated a slight increase in 4-HC toxicity in the same experiments. The observation that IL-1 was still protective even when a purified cell population depleted of accessory cells was used is suggestive of a direct effect of IL-1. Our data also suggest that early progenitor cells including the replatable B;-CFC are the main target of that protection. We believe that using this in vitro assay system will enable us to investigate the possible mechanisms responsible for the protection of these primitive progenitors. From a clinical perspective, future studies should attempt to clarify whether protection by IL-1 is selective for normal hematopoietic cells versus malignant cells and whether these protected primitive progenitors represent the pluripotent stem cells responsible for engraftment of transplanted bone marrow by using an animal model system.