Immune recovery and the role of recent thymic emigrated T lymphocytes after pediatric hematopoietic stem cell transplantation.

BACKGROUND AIMS: Adequate re-establishment of thymopoiesis is critical for long-term immune reconstitution after hematopoietic cell transplantation (HCT), potentially impacting patient survival rates. This study aimed to evaluate immune reconstitution in pediatric HCT recipients by quantifying recent thymic emigrants (RTEs), specifically CD3+CD31+CD45RA+ cells. METHODS: We conducted a retrospective analysis of 186 pediatric patients transplanted between 2013 and 2020, undergoing their first allogeneic HCT, who were alive in the first 100 days after transplantation with immune recovery evaluation at three time points: day 100, day 180 and day 360 after HCT. We analyzed the distribution of peripheral blood subsets of T, B and natural killer lymphocytes and assessed the impact of underlying disease, HCT type, stem cell source, recipient age, conditioning regimen, graft-versus-host disease (GVHD) occurrence and cytomegalovirus (CMV) reactivation on immune recovery. RESULTS: At day 100, patients under 10 years exhibited higher RTE CD4+ and CD8+CD31+CD45RA+ counts compared with older patients (5.3 versus 2.2 cells/µL, P = 0.022 and 48 versus 72.8 cells/µL, P = 0.049, respectively). Patients with haploidentical HCT had lower RTE CD4+ counts compared with those with unrelated or related donors (2.4 versus 4.4 versus 7.9 cells/µL, P = 0.024). Administration of rabbit anti-thymocyte globulin negatively impacted RTE CD4+ production (median, 6.5 versus 2.4 cells/µL, P = 0.007). At day 180, the presence of GVHD had a negative influence on RTE production (11.7 versus 56.8 cells/µL, P < 0.001), particularly higher-grade acute GVHD (without, 56.8 cells/µL, grade 1-2, 28.1 cells/µL, grade 3-4, 6.0 cells/µL, P < 0.001). Patients with CMV reactivation had higher CD8+CD31+CD45RA+ compared with those without reactivation (median, 204.6 versus 100.2 cells/µL, P = 0.022). At day 360, no variables significantly affected RTE recovery. Overall survival at 5-year follow-up was 87.7%, with a median of 1170 days (range, 122-3316). Multivariate analysis showed that age >10 years (P = 0.038), negative CMV donor serology (P = 0.0029) and acute GVHD (P = 0.0026) had a negative impact on survival. CONCLUSIONS: This study highlights variations in RTE production based on patient age, donor type and immunosuppression regimen employed.

Immune reconstitution after allogenic stem cell transplantation: An observational study in pediatric patients.

INTRODUCTION: The immune reconstitution (IR) after the allogenic hematopoietic stem cell transplantation (allo-HSCT) is a progressive process intrinsically correlated to the therapeutic success. It is essential to understand the interfering factors in IR to prevent the HSCT-related mortality. METHODS: We retrospectively evaluated the clinical outcomes, absolute lymphocyte counts (ALCs) and lymphocyte subtypes at different time-points of 111 pediatric patients with allogeneic HSCT for malignant and non-malignant diseases from 2013 to 2018. RESULTS: The ALCs gradually increased on D+30, D+100, and D+180 (medians 634/µL, 1022/µL and 1541/µL, respectively). On D+100, the CD3+CD8+ achieved the highest recovery rate (68%), followed by the CD16+CD56+ (47%), CD3+CD4+ (39%) and CD19+ (8%). The adequate ALC recovery was associated with age < 8 years, bone marrow grafts, myeloablative conditioning, non-use of serotherapy and non-haploidentical donors. The ALC and CD3+CD8+ on D+100 counts were higher in patients with the cytomegalovirus infection. The CD3+CD4+ recovery was associated with an age < 8 years, a non-malignant disease and a lower incidence of acute graft-versus-host disease ≥ grade 2. Furthermore, the ALC recovery on D+100 resulted in a higher overall survival, regardless of the disease type (HR 3.65, 1.05 - 12.71, p = 0.04). CONCLUSION: Several factors influenced the IR after the allo-HSCT. The ALC ≥ 500/µL on D+100 was a simple IR predictor of survival, easily available to resource-limited centers.

Immune reconstitution after allogenic stem cell transplantation: An observational study in pediatric patients

Abstract Introduction The immune reconstitution (IR) after the allogenic hematopoietic stem cell transplantation (allo-HSCT) is a progressive process intrinsically correlated to the therapeutic success. It is essential to understand the interfering factors in IR to prevent the HSCT-related mortality. Methods We retrospectively evaluated the clinical outcomes, absolute lymphocyte counts (ALCs) and lymphocyte subtypes at different time-points of 111 pediatric patients with allogeneic HSCT for malignant and non-malignant diseases from 2013 to 2018. Results The ALCs gradually increased on D+30, D+100, and D+180 (medians 634/μL, 1022/μL and 1541/μL, respectively). On D+100, the CD3+CD8+ achieved the highest recovery rate (68%), followed by the CD16+CD56+ (47%), CD3+CD4+ (39%) and CD19+ (8%). The adequate ALC recovery was associated with age < 8 years, bone marrow grafts, myeloablative conditioning, non-use of serotherapy and non-haploidentical donors. The ALC and CD3+CD8+ on D+100 counts were higher in patients with the cytomegalovirus infection. The CD3+CD4+ recovery was associated with an age < 8 years, a non-malignant disease and a lower incidence of acute graft-versus-host disease ≥ grade 2. Furthermore, the ALC recovery on D+100 resulted in a higher overall survival, regardless of the disease type (HR 3.65, 1.05 - 12.71, p= 0.04). Conclusion Several factors influenced the IR after the allo-HSCT. The ALC ≥ 500/μL on D+100 was a simple IR predictor of survival, easily available to resource-limited centers.