ABSTRACT
Donor T lymphocytes, because they protect against infection, mediate antitumor effects,
and prevent graft rejection, yet cause graft-vs.-host disease (GVHD), represent a double-
edged sword as a cell component of bone marrow or peripheral blood allografts. An ability
to augment or preserve beneficial allogeneic T-cell effects, while limiting detrimental
GVHD, is an essential requirement for further optimization of allogeneic hematopoietic
stem cell transplantation (SCT). One emerging area of immunology relevant to this
challenge involves the study of T-cell cytokine phenotypes. In this chapter we provide
an update on current Th1/Th2 research, review this biology as it relates to GVHD pathogenesis, and consider how this insight may provide an opportunity for modulating
allogeneic T-cell immune responses and effects.
