The important balance between cytokines derived from type 1 and type 2 helper T cells in the control of graft-versus-host disease.

We have investigated cytokine mRNA expression in the peripheral blood mononuclear cells of 20 patients who received allogeneic hematopoietic stem cell transplants to assess the cytokine network after transplantation. IL-4 mRNA expression decreased in five of five (100%) patients with > or = grade III (severe) acute GVHD and increased in 10 of 22 (45%) patients without severe GVHD. In contrast, IL-12 mRNA expression increased in two of two (100%) patients with severe GVHD, but increased in only six of 18 (33%) patients without severe GVHD. Furthermore, IL-10 and/or IL-13 mRNA expression increased in 19 of 22 (86%) patients without severe GVHD, but increased in only one of three (33%) patients with severe GVHD. In patients with allogeneic PBSCT who had severe acute GVHD, the cytokine mRNA expression in patients with allogeneic PBSCT, who had no severe GVHD, showed a similar pattern to that in patients with allogeneic BMT. IL-4 mRNA expression increased in three of five (60%) patients and IL-10 and/or IL-13 mRNA expression increased in five of five (100%) patients. In contrast, IL-12 mRNA expression increased in only one of three (33%) patients. Serum IL-4 concentration in allogeneic PBSCT patients in the early engraftment phase was relatively high, while serum IL-12 concentration was low. These findings suggest that severe GVHD may be related to the cytokine imbalance between type 1 helper T (Th1) cells and type 2 helper T (Th2) cells.