IL-1 has putative chemo- and radioprotective properties, but its effects on primitive hemopoietic stem cell (PHSC) and early multilineage precursor function when given with these modalities is unknown. C57BL6/J (B6) mice, given IL-1 20 h before cyclophosphamide (200 mg/kg for four biweekly doses) or before irradiation (500 cGy), were sacrificed after 4 wk. Their marrow was used as donor cells, and that from B6- Hbb dGpi1a (B6-GPI) mice was used as competitor cells in competitive repopulation. Percentages of B6 cells were measured at 30 and 150 days. Stem cell numbers were estimated using binomial statistics. IL-1 alone did not affect stem cell function. As expected, significant declines in early multilineage precursor and PHSC function occurred with chemotherapy and radiation alone. IL-1 with chemotherapy led to exacerbation of these losses in function and numbers ( p 0.05). A similar reduction in function occurred using IL-1 before irradiation. In summary, IL-1 with chemotherapy or radiation worsened chemotherapy- and radiation-induced functional damage to PHSC and other hemopoietic precursors, suggesting that improvements in survival do not necessarily translate into preservation of hemopoietic function.
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