Graft-versus-Leukemia and Graft-versus-Host Reactions after Donor Lymphocyte Infusion Are Initiated by Host-Type Antigen-Presenting Cells and Regulated by Regulatory T Cells in Early and Long-Term Chimeras

The effect of Thy1⁺ T_reg cell depletion on DLI-induced GVHD waned with time. In the first column, survival curves are shown for Thy1.2-depleted (n = 12 per group for each time point) or -nondepleted (n = 10-11 per group for each time point) B6-into-AKR/J complete donor HSC chimeras given a DLI with 3 × 10⁷ Thy1.1⁺ B6.PL splenocytes at day 28 (A), day 35 (B), day 42 (C), day 49 (D), or day 70 (E) after BM transplantation. The second and third columns contain flow cytometric histograms depicting the percentages of splenic Thy1.2⁺ cells in representative animals at each time point that had been treated or not treated with anti-Thy1.2 mAb. The survival data represent the combined results of 2 independent experiments, all time points were included in each of the experiments, and the mice in each experiment were given BM transplants on the same day and then given DLI at the indicated time points. Statistical comparisons (P values) for the 2 survival curves in each graph are shown (ns = not significant).

The DLI-induced GVL effect in day 28 complete donor HSC chimeras was absent in day 100 complete chimeras. Survival (A and B) and body weight changes (C and D) are shown for DLI-treated or -nontreated day 28 (A and C) or day 100 (B and D) complete donor HSC chimeras that were subsequently challenged with 10³ AKR M2 leukemia cells 1 week after DLI (ie, day 35 and day 107, respectively). Animals that were given HSCT only (no DLI or leukemia) served as controls. The data represent the combined results of 4 independent experiments for the day 100 chimeras and 3 independent experiments for the day 28 chimeras. Each experimental group was repeated at least once. The total numbers of mice in each group are shown in (C) and (D). BMT, bone marrow transplantation.

Depletion of CD25⁺ T_reg was unable to restore the DLI-induced GVL effect in day 100 complete donor HSC chimeras. Survival (A) and body weight changes (B) are shown for day 100 complete donor chimeras treated or not treated with in vivo–depleting anti-CD25 mAb and/or DLI and then challenged with 10³ AKR M2 leukemia cells 1 week later (day 107). The data for the anti-CD25 + M2 and anti-CD25 + DLI + M2 experimental groups represent the combined results of 4 independent experiments. Each group was included in at least 2 of the 4 experiments, which were all completed within a 9-month time period. The survival curves for the BM transplantation only, M2, and DLI + M2 groups are the same as in Figure 2, and they are shown simply to provide comparative survival data for the anti-CD25 + M2 and anti-CD25 + DLI + M2 experimental groups. The total numbers of mice in each group are shown in (B) BMT, bone marrow transplantation.

A DLI-induced GVL effect was observed in day 100 mixed chimeras without concurrent GVHD. Survival (A) and body weight changes (B) are shown for DLI-treated or -nontreated day 100 mixed HSC chimeras that were subsequently challenged with 10³ AKR M2 leukemia cells 1 week after DLI (day 107). Controls that received BM only (no tumor) were included in these experiments. The data represent the combined results of 3 independent experiments. Each group was included in at least 2 of the 3 experiments. The total numbers of mice in each group are shown in (B). BMT, bone marrow transplantation.

Infusion of host-type DCs partially restored DLI-induced GVH/GVL reactivity in long-term complete donor chimeras. Survival (A and B) and body weight changes (C and D) are shown for day 100 complete donor chimeras given 2.5 × 10⁶ (A and C) or 5 × 10⁶ (B and D) host-type DCs with or without DLI followed by challenge with 10³ AKR M2 leukemia cells at day 107. The data represent the combined results of 3 independent experiments. Each group was included in at least 2 of the 3 experiments that were all performed within a 3-month time period. The total numbers of mice in each group are shown in (C) and (D). The survival curve for the BM transplantation only (no tumor) group is the same as that shown in Figure 2B, and it is shown to provide comparative survival data for the other experimental groups. For the mice given 5 × 10⁶ DCs (D), body weight loss in the DLI + DC + M2 group was significantly greater than that in the DC + M2 group at days 7 and 14 after tumor challenge, as indicated by the asterisks, (P < .03). BMT, bone marrow transplantation.

Infusion of host-type DCs did not enhance DLI-induced GVHD in short-term day 28 complete donor chimeras. Survival (A) and body weight changes (B) are shown for day 28 complete donor chimeras given DLI with or without 5 × 10⁶ host-type DCs. Controls that received BM transplantation only were included in these experiments. The data represent the combined results of 3 independent experiments. Each group was included in at least 2 of the 3 experiments, and the total numbers of mice in each group are shown in (B). The survival curve for the BM transplantation–only group is the same as that shown in Figure 2A, and it is shown to provide comparative survival data for the other experimental groups. BMT, bone marrow transplantation.

Depletion of CD25⁺ cells increased GVH/GVL reactivity in long-term BM chimeras coinfused with host DCs and DLI. Survival (A and B) and body weight changes (C and D) are shown for CD25-depleted or -nondepleted day 100 complete donor chimeras given 2.5 × 10⁶ (A and C) or 5 × 10⁶ (B and D) host-type DCs with or without DLI followed by challenge with AKR M2 leukemia cells at day 107. The data for the anti-CD25–treated groups represent the combined results of 3 independent experiments. Each group was included in at least 2 of the 3 experiments that were all performed within a 6-month time period. The total numbers of mice in each group are shown in (C) and (D). Survival curves for the DC + M2 and DLI + DC + M2 groups are the same as those shown in Figure 5, and they are shown to provide comparative survival data for the other experimental groups.