Biological Properties of Cells Other Than HSCs

The array of cellular players involved in the biology of hematopoietic cell transplantation (HCT) clearly extends beyond hematopoietic stem cells (HSCs) themselves and, in the case of transplantation from allogeneic sources, importantly includes cells of the innate and adaptive immune systems. Historically, the discovery of the human leukocyte antigen (HLA) system and the functional characterization of the different immune cell types had a transformational impact on our current understanding of the pathobiological “sequelae” of allo-HCT (rejection, graft-versus-host disease (GVHD), graft-versus-leukemia (GVL) effect). This body of knowledge coupled to the most recent “exploitation” of biotechnology has allowed us to design strategies for in vivo stimulation or adoptive transfer of specific immune cell types with the potential to dramatically improve transplantation outcome.