Blood stem cell transplantation: factors influencing cellular immunological reconstitution

Lymphocyte subset analysis for the assessment of treatment-related complications after autologous stem cell transplantation in multiple myeloma

BACKGROUND AIMS

The aim of this study was to investigate the correlation between infused lymphocyte populations and lymphocyte subsets at engraftment, and the early clinical implications of lymphocyte subset recovery after autologous stem cell transplantation (ASCT) in multiple myeloma (MM).

METHODS

We examined the lymphocyte populations of infused autografts and the lymphocyte subsets of peripheral blood at engraftment from 50 patients using flow cytometry. Each subset was grouped as low (below median) and high (above median) to examine the correlation with mucositis of grade 3 or more and the occurrence of infections and cytomegalovirus (CMV) reactivation.

RESULTS

Using Spearman correlation coefficients, we found that cell doses of infused CD8(+) (P = 0.042) and CD19(+) cells (P = 0.044) were significantly associated with the absolute lymphocyte count (ALC) at engraftment. The dose of infused CD34(+) cells was not associated with the change of lymphocyte subsets except for an inverse correlation with CD4(+) cells (P = 0.006). After adjusting for potential variables in univariate analysis, multivariate analyzes revealed that the lower ratio of infused CD4(+) to CD8(+) cells (P = 0.030) was an independent factor for severe mucositis. Of lymphocyte subsets at engraftment, a higher frequency of CD3(+) (P = 0.024) and a lower frequency of CD56(+) (P = 0.020) were independent predictors for infections after engraftment. A higher frequency of CD8(+) cells (P = 0.041) and a lower ratio of CD4(+) to CD8(+) (P = 0.021) were independent predictors for CMV reactivation.

CONCLUSIONS

Our data suggest that lymphocyte subset analysis of infused autograft and peripheral blood at engraftment may provide new predictors for early complications after ASCT in patient with MM.

Endothelial cells from hematopoietic stem cells are functionally different from those of human umbilical vein

Hematopoietic stem cells have a remarkable plastic capacity, which allows them to differentiate into various cells, such as immune cells, nervous cells, muscle cells, bone and cartilaginous cells. The aim of this study was to show the capacity of stem cells to differentiate into endothelial cells, in culture, after addition of endothelial cells growth supplement (ECGS). We also compared the behavior of these cells with that of endothelial cells obtained from human umbilical vein (HUVEC). CD34+ cells obtained by immunomagnetic separation from human umbilical cord and placental blood were used. After 12-15 days of culture in a medium containing ECGS, the cells showed morphological changes characteristic to endothelial cells and immunocytochemical analysis revealed the presence of CD31 surface antigen and von Willebrand factor. The flow-cytometric analysis of endothelial cells adhesion molecules (ECAM) showed that endothelial cells derived from CD34+ cells expressed CD54/ICAM-1 9.65+/-0.2% and CD106/VCAM 7.73+/-0.3%, values similar to those expressed by HUVECs. After TNF incubation, ECAM expression increased only in HUVECs. These data demonstrate that a fraction of circulating CD34+ cells may develop some endothelial cell characteristics when cultured with ECGS, but they are functionally different from HUVECs.

The whys and hows of hematopoietic progenitor and stem cell mobilization

Intentional mobilization of hematopoietic/stem cells into the circulation has improved the efficiency of their collection. Transplantation of mobilized blood stem cells to patients with marrow aplasia results in a faster pace of hematopoietic recovery than transplantation of marrow-derived stem cells. Autologous and allogeneic hematopoietic stem cell transplantation are increasingly performed with blood-derived cells. Donors of both autologous and allogeneic blood stem cells do not always respond well to therapies designed to produce mobilization. Autologous donors may respond poorly as a result of myelotoxic damage inflicted by prior antitumor therapy, but this explanation is not valid for allogeneic donors. The mechanism(s) involved in the process of mobilization are incompletely understood. Until these mechanisms are elucidated, methods to improve mobilization vigor on a rational basis will not be obvious. In the meanwhile, clinical observations may provide some hints regarding the whys and hows of mobilization and permit incremental improvements in this process.