Background and objectives: Graft-versus-host disease (GvHD) remains a major complication of allogeneic stem cell transplantation (SCT) and donor lymphocyte infusions (DLI). CD25-expressing donor T cells may be involved in the prevention or induction of GvHD as these cells comprise both CD4 +CD25+ regulatory T (Treg) cells and preactivated CD4+ or CD8+ conventional T cells. Therefore, we evaluated the relationship between CD25-expressing CD4+ and CD8+ donor T cells and the clinical outcome of DLI.
Design and methods: We retrospectively studied the DLI products of 47 HLA-identical DLI recipients by FACS analyses. As Treg cells are often identified within the CD4 +CD25hiCD45RB low subset, we determined the frequencies of CD4+ and CD8+ T cells with different expression levels of CD25 and CD45RB.
Results: The frequencies or infused doses of donor CD4 +CD25+ T cells, regardless of their CD25 and CD45RB expression levels, showed no correlation with the clinical outcome in univariate and multivariate analyses. In contrast, elevated frequencies of donor CD8+CD25+ T cells showed significant correlations with grade II-IV acute GvHD. Patients with GvHD also appeared to have received higher doses of CD8+CD25+ cells. Increased frequencies of CD8+CD25+ cells in the DLI products and the infused-doses of these cells also correlated with complete remissions accompanying GvHD. However, there was no correlation between increased levels of CD8 +CD25+ cells with complete remissions achieved in the absence of a clinically apparent acute GvHD.
Interpretation and conclusions: Donor CD8 +CD25++ T cells appear to represent a risk factor for GvHD in the DLI setting. Selective depletion of these cells from DLI products may attenuate GvHD without significantly compromising anti-tumor efficacy.