Background. Tumor necrosis factor-α (TNF-α) is known to be a critical effector molecule in the pathogenesis of graft-versus-host disease (GVHD), and elevated levels during bone marrow transplantation (BMT) conditioning are associated with more severe GVHD. Many patients receive chemotherapy prior to BMT, but its effect on subsequent toxicities is controversial. Methods. We studied the effect of prior chemotherapy on GVHD severity and inflammatory cytokine generation in a well-established murine model of allogeneic BMT (B6 → B6D2F1). Results. Three weeks after a single dose of cyclophosphamide, bone marrow and splenic cellularity was reduced by 50% and the production of TNF-α to LPS stimulation by macrophages was also markedly impaired (both before and after total body irradiation). Allogeneic BMT recipients previously treated with cyclophosphamide had significantly less GVHD and improved survived relative to recipients previously pretreated with diluent only. This survival advantage was associated with reduced systemic levels of both TNF-α and interleukin-1β 7 days after BMT. This reduction occurred despite equivalent serum levels of lipopolysaccharide, consistent with the reductions in TNF-α and interleukin-1β production by host macrophages after cyclophosphamide pretreatment. Conclusions. These data support the notion that patients entering BMT conditioning without prior cytotoxic treatment (e.g., patients with chronic myeloid leukemia) may be at increased risk of posttransplant complications associated with excessive inflammatory cytokine production.
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