Immune reconstitution after autologous hematopoietic transplantation with Lin^-, CD34⁺, Thy-1^lo selected or intact stem cell products

In sequential studies, we compared immune reconstitution following high-dose chemotherapy (HDT) and stem cell transplantation (SCT) using intact mobilized peripheral blood stem cell (PSC) in intermediate grade non-Hodgkin's lymphoma (NHL) patients and CD34⁺, lineage-negative (Lin^-), Thy-1^lo (CD34⁺Lin^-Thy-1^lo) stem cells in low-grade NHL patients. Cytokine expression and cellular phenotype and function were used as the basis of comparison. Despite differences in cellular composition of the stem cell grafts, immune reconstitution in both groups was similar. Significantly higher levels of type 1- and 2-associated cytokine messenger ribonucleic acid (mRNA) were observed both prior to and following transplant in the peripheral blood (PB) of both cohorts as compared to normal individuals. Similar levels of interleukin (IL)-4, IL-10, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α) messenger ribonucleic acid (mRNA) were seen in PB mononuclear cells following transplant with either product. In contrast, patients receiving isolated CD34⁺Lin^-Thy-1^lo cells expressed significantly higher IL-2 levels at all times examined post-transplant. Despite the high levels of cytokine gene expression and rapid restoration to pretransplant levels of CD3 cell number by day 30, T cell function and CD4:CD8 and CD4⁺CD45RA:CD4⁺CD45RO⁺ ratios were significantly depressed in both cohorts compared to normal donors, and significantly lower in patients transplanted with CD34⁺Lin^-Thy-1^lo compared to patients receiving an intact PSC product. These data suggest that the peripheral tolerance in patients receiving HDT and an autologous SCT occurs independent of graft composition, although immune function and CD4 recovery are better facilitated by transplantation of an intact product.