Blood, Vol. 96 No. 3 (August 1), 2000:
pp. 1144-1149
Recipient elimination of allogeneic lymphoid cells: donor
CD4+ cells are effective alloantigen-presenting cells
Loren D. Fast
From the Department of Medicine, Rhode Island Hospital and Brown
University, Providence, RI.
The encounter with allogeneic major histocompatibility complex (MHC)
molecules expressed on donor leukocytes during transfusion of blood
products has been shown to impact the recipient's immune responses in
a number of settings. To better understand the responses induced by the
transfer of allogeneic cells, a murine model was used to characterize
the recipient responses that control the fate of the allogeneic
lymphoid cells. Recipient CD8+ cells could rapidly
eliminate a large number of donor cells within 3 days after injection.
When elimination responses were studied in the absence of
CD8+ cells, it was found that alloantibody production was
the secondary elimination mechanism. Optimal recipient
CD8+ and B cell responses in this model required help
from CD4+ cells that could be provided by 3 different
pathways. Although recipient CD4+ cells could provide
help when activated by direct recognition of allogeneic MHC class II
molecules expressed on donor cells or by indirect recognition
of processed alloantigen presented on recipient
antigen-presenting cells (APCs), the most rapid recipient responses
were generated by help provided by donor CD4+ cells.
Purified donor CD4+ cells were also able to induce these
rapid responses, indicating that activated donor CD4+
cells expressing allogeneic MHC molecules were able to effectively stimulate responses by both recipient CD8+ and B cells.
