Role of IL-4-Producing CD8+ T Cells in Patients with Chronic Graft-Versus-Host Disease (cGVHD) and in Normal Healthy Volunteer.

The pathophysiology of cGVHD still remains unclear. To gain more insight into the immunological mechanism of cGVHD, we examined surface marker and cytokine production of peripheral blood T cells from 19 patients in the chronic phase of allogeneic hematopoietic stem cell transplantation (allo-HSCT). The median age of patients was 31 years (range 13–47 years). The median days from allo-HSCT to examination was 43 months (range 17–94 months). Ten patients in whom 6 have treated with immunosuppressive agents and 4 without them developed chronic GVHD, whereas 9 patients in whom 5 have treated with immunosuppressive agents and 4 without them did not develop chronic GVHD. Peripheral blood mononuclear cells were extracted from patients and 10 healthy volunteers, followed by isolation into CD4+ T cells and CD8+ T cells. The analysis of surface marker and intracellular cytokine production of these cells was performed using fluorescence activated cell sorter. The percentage of IFN-g-producing CD8+ T cells among CD8+ T cells was significantly higher in patients with or without cGVHD than in healthy volunteers (p<0.001). Since all 19 patients were in remission, the IFN-g-producing CD8+ T cells might be related to graft-versus-leukemia effect. On the other hand, the percentage of IL-4-producing CD8+ T cells among CD8+ T cells was significantly higher in patients with cGVHD (mean 3.3%, range 1.3–8.2%) than in patients without cGVHD (mean 1.2%, range 0.8–1.7%) and healthy volunteers (mean 1.1%, range 0.1–1.6%) (both p<0.001). By contrast, the percentage of IL-4-producing CD4+ T cells was not different among patients with and without cGVHD and healthy volunteers. Then, we minutely explored the immunological role of IL-4-producing CD8+ T cells in healthy volunteers. These cells expressed the surface marker of CD25, CCR4 and CTLA-4. In the analysis of cytokine production in these cells, we identified the type 2 cytokine, such as IL-4, IL-5, IL-10, and IL-13, although we could not find IFN-g. In conclusion, these findings suggest that IL-4-producing CD8+ T cells may be an immunological marker of cGVHD in which these cells may play a crucial role as regulatory T cells.