Cytokine-mediated nitric oxide release--a common cytotoxic pathway in host-versus-graft and graft-versus-host reactions?

Serial cytokine and nitrate (as a measure of nitric oxide production) levels were assayed in nine consecutive patients undergoing allogeneic haemopoietic stem cell transplants. They were compared to those in 13 patients undergoing autologous transplants (transplant controls), 15 neutropenic patients with infective complications (patient controls) and 27 blood donors (normal controls). Peak nitrate, interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) levels were significantly higher in four allogeneic transplant patients with major non-infective complications compared to those without such complications, and control groups. Cytokine and nitrate levels peaked during conditioning therapy in the patients with veno-occlusive disease (one patient) and fulminant cholestatic liver failure (one patient), indicating that tissue damage may have been initiated during chemoradiotherapy in these patients, whereas peak levels occurred 2-3 days before graft rejection (one patient) and severe graft-versus-host disease (one patient), indicating a role for cytokine-induced nitric oxide release in the pathophysiology of these immune-mediated complications. Based on the data presented, it can be tentatively postulated that nitric oxide is a common proximate regulator of the immune response in host-versus-graft and graft-versus-host reactions.