The use of recombinant cytokines for enhancing immunohematopoietic reconstitution following bone marrow transplantation. II. The influence of lymphokines on CFU-GM colonies from human untreated, ASTA-Z or Campath-1M treated bone marrow

Patients undergoing bone marrow transplantation (BMT) are subjected to the risk of pancytopenia in the immediate post-BMT period. Recipients of bone marrow (BM) autografts purged in vitro by chemical agents such as mafosfamide (ASTA-Z) are even more likely to develop a delayed engraftment. In a previous study in mice, we showed earlier immunohematopoietic reconstitution after syngeneic marrow grafting with BM cells precultured with single or combined cytokines. In this work we determined optimal culture conditions for the use of single and various cytokine combinations in order to activate progenitor cells following in vitro cultures of untreated, ASTA-Z purged or T cell-depleted human BM preparations prior to BMT. The best single cytokine for enhancing CFU-GM was found to be GM-CSF (0.1 mg/ml) which produced an increase of up to 8-fold over controls after 3 days' incubation. Addition of recombinant human interleukin 3 (rhIL3) (0.1 mg/ml) to rhGM-CSF had an additive effect. The same enhancing effect of in vitro CFU-GM by both cytokines was observed following ASTA-Z purging of BM cells obtained from patients undergoing autologous BMT. Similarly, depletion of lymphocytes from BM using the monoclonal rat anti-human lymphocyte antibody Campath-1M and human complement did not diminish the beneficial influence of rhIL3 and rhGM-CSF. When combined with rhGM-CSF and rhIL3, rhIL1 and rhIL2 had no appreciable enhancing effect on CFU-GM and occasionally even reduced it. We suggest that enhancement of differentiation of hematopoietic progenitor cells may be accomplished by in vitro incubation of BM cells without continuous administration of cytokines in vivo following BMT.