Immunologic attributes of cytokine mobilized peripheral blood stem cells and recovery following transplantation

The immunologic attributes of cytokine mobilized peripheral blood stem cell (PSC) products (n = 52) and the resulting reconstitution of the hematopoietic and immunologic system following autologous transplantation were examined in a consecutive population of non-Hodgkin lymphoma (NHL), or solid tumor patients at the University of Nebraska Medical Center. Granulocyte-monocyte colony stimulating factor (GM-CSF)-mobilized PSC products had a high frequency of monocytes (31%) and bands (15%) as compared to normal peripheral blood (PB) cells. The phenotypic analysis of the mobilized PSC product revealed that they had normal levels of CD4⁺ cells, an increased frequency of CD8⁺ cells and a corresponding decrease in the CD4⁺:CD8⁺ cell ratio as compared to the peripheral blood leukocytes (PBL) of normal individuals. PSC products also had an increase in CD34⁺ cells as compared to PB. Natural killer (NK) and T cell activity in the PSC products were also lower than that observed in PB. Post-transplantation there was an accelerated reconstitution of NK-cell function in the PB as compared to T cell function (PHA (phytohemagglutinin) mitogenesis) which did not return to normal by day 100 post-transplantation. We also report for the first time high levels of an irradiation resistant suppressor cell activity in the PSC product and in the PB post-transplantation. There was also a concomitant increase in CD4^-, CD8^-, TCR α/β⁺ cells (phenotypic homolog of 'natural suppressor' (NS) cells) in the PB post-transplantation. The number of months of prior chemotherapy correlated with PHA response but the NS activity and frequency of CD4^-, CD8^- and TCR α/β⁺ cells did not. Further, cytokine mobilization and apheresis appears to contribute to the loss of PHA responsiveness and the increased levels of suppressor cell activity.