Characterization of T-cell clones derived from peripheral blood lymphocytes of a patient with transfusion-associated graft-versus-host disease: Fas-mediated killing by CD4+ and CD8+ cytotoxic T-cell clones and tumor necrosis factor beta production by CD4+ T-cell clones.

Transfusion-associated graft-versus-host disease (TA-GVHD) is one of the most serious adverse effects of blood transfusion. It is generally thought to be caused by the infused lymphocytes. Donor-derived cytotoxic T lymphocytes (CTLs) directed against the recipient's HLAs, which have escaped the recipient's immune system and are proliferating, are considered to attack recipient organs and tissues. Despite the seriousness of the disease, the precise mechanism of its development remains unclear and no definitive treatment has been developed. With the aim of developing an effective treatment, we established and characterized T-cell clones from peripheral blood lymphocytes (PBLs) of a TA-GVHD patient. Three types of clones were established. Type I clones were CD8+ and specifically lyse cells that express HLA B52. Type II clones were CD4+, specifically lysed cells that express HLA DR15, and proliferated in response to stimulation with cells that express DR15. Type III clones were also CD4+, showed no cytotoxic activity toward any HLA-expressing cells, and proliferated in response to stimulation with cells that express DR15. Furthermore, we found that the Fas/Fas-ligand (Fas-L) system is involved in the cytotoxicity of the type I and II clones and that the type III clones produce and secrete a large amount of tumor necrosis factor beta (TNFbeta) after antigen stimulation. Based on our results, these three types of clones can be classified into two categories: those that have the ability to induce GVHD directly by cytolysis and that show no cytotoxic activity and those that have the ability to cause GVHD indirectly through secretion of cytotoxic lymphokines.