Recovery of lymphocyte and dendritic cell subsets after autologous CD34+ cell transplantation

Following high-dose chemotherapy (HDC) and peripheral blood progenitor cell transplantation (PBPCT), there are profound changes in leukocyte homeostasis and the immune system is compromised. Transplantation of purified CD34(+) cells may further compromise immune recovery because the grafts are depleted of mature immune cells. However, a detailed monitoring of immune cell reconstitution has not been done. We monitored blood levels of antigen-presenting cells (APC) and of lymphocytes by multi-color flow cytometry at different times post CD34(+) PBPCT. We found a rapid normalization of circulating levels of the antigen-presenting CD11c(+) dendritic cells (defined as lineage(-) HLA-DR+ CD11c(+) cells). There was a slight over-representation of lin(-) DR+ CD11c(-) cells at day 42 post transplantation suggesting that the composition of the APC population might be affected. Normal levels of total T, B and NK lymphocytes were rapidly achieved but the composition of the T cell population was abnormal. Patients had elevated levels of CD8(+) T cells at early times and a persistent reduction in levels of naive CD8(+) T cells (CD8(+) CD4- CD45RA(+) CD27(+)) and of naive CD4(+) T cells (CD4(+) CD3(+) CD8(-) CD45RA(+)). Thus, we found a rapid recovery of DC after CD34(+) PBPCT but the specific numerical defects in naive T cells are likely to be a major cause of immune dysfunction in the patients.