Background: After hematopoietic cell transplantation (HCT), there is a prolonged period of immune deficiency.
Objective: To review the recovery of immunity after HCT, including how it is influenced by the cellular contents of the graft, and therapeutic implications.
Methods: Literature review using Medline.
Results/conclusion: Whereas innate immunity (e.g., epithelial barriers, phagocytes, natural killer cells) typically recovers within weeks post-transplant, the recovery of adaptive immunity takes longer, months for B cells and years for T cells. The recovery is influenced by the graft contents. For example the number of CD34 cells given with the graft affects the tempo of neutrophil recovery, and the number of CD4 T cells given with the graft affects CD4 T cell counts post-transplant. Improved understanding of the relationship between graft contents and immune reconstitution could lead to graft engineering improving transplant outcomes.