Immune Reconstitution following Myeloablative Allogeneic Hematopoietic Stem Cell Transplantation: The Impact of Expanding CD28^negative CD8⁺ T Cells on Relapse

Median absolute counts of peripheral blood CD8⁺ T cells (a) and their CD28-negative subset (b) by days 30, 60, 90, 180, and 365 after myeloablative HLA-matched allo-SCT, comparing patients free of any clinical complication throughout 395 to 1564 days of follow-up (diamonds and thick solid line) with patients who experienced only cGVHD (triangles and thin solid line) and patients with relapse (squares and dashed line) exclusive of other complication. Error bars indicate the 25th to 75th percentiles. The number of patients studied who were complication-free, who had only cGVHD or only malignant relapse were 17, 13, and 14, respectively, on days 30; 18, 13, and 15 on day 60 and on day 90; 16, 13, and 10 on day 180; and 8, 10, and 8 on day 365. Positions are depicted next to each other around the time point to prevent overlaying 1 subgroup value with another. The horizontal dotted line in (a) denotes the fifth percentile of reference values for the median age of the recipients. ∗P ≤ .05; ∗∗P ≤ .01; ∗∗∗P ≤ .001 by Kruskal Wallis test with Dunn's posttest evaluation to compare complication-free patients with those who relapsed; differences between complication-free patients and patients with only cGVHD were not significant whatever the time point.

Kaplan-Meier estimate of malignant relapse after myeloablative HLA-matched allo-SCT. The 80 patients were categorized as having absolute CD28^neg CD8⁺ T cell numbers by day 60 postgraft falling lower (solid line) versus equal to or higher than (dashed line) the median (179 CD28^neg CD28⁺ T cells/mm³ of peripheral blood) determined in the subgroup of 18 patients free of any clinical complication by the time of last follow-up. The P value is for the log-rank test.