Immune Reconstitution Following Allogeneic Hematopoietic Stem Cell Transplantation

Abstract

Objective: To evaluate pattern of immune reconstitution (IR) following allogeneic hematopoietic stem cell transplantation (HSCT)

Methodology: This observational study was conducted at Department of Clinical Hematology and Bone Marrow Transplant, Quaid-e-Azam International Hospital Islamabad from January 2023 to December 2024. Sixty-two consecutive patients undergoing allogeneic HSCT for various hematological diseases were evaluated. Following parameters were recorded at 6 and 12 months post-HSCT: Absolute lymphocyte count (ALC), lymphocyte subsets and immunoglobulin levels. Patients with incomplete follow up or graft failure/rejection were excluded from analysis

Results: Absolute lymphocyte count recovery was seen in 77.4% of patients by 6 months which increased to 87.1% at 12 months post-HSCT. CD3+CD8 cells recovery was seen in 91.90% while 54.8%, 33.90% & 22.6% respectively had CD16+CD56+, CD19+ and CD3+CD4 cells recovery by 6 months post-HSCT. Percentage of patients with CD3+CD4 recovery increased to 61.3%, while other subset recovery percentages were: CD3+CD8+ 90.3 %, CD16+CD56+ 43.5 % and CD19+ cells in 51.6 % by 12-months post-HSCT. Immunoglobulin recovery at 6 months was observed in 79%, 85.4%, and 90.3% of patients for IgA, IgG, and IgM respectively and at 12 months 83.9%, 88.7%, and 82.3% of patients had normal levels of IgA, IgG, and IgM respectively. Early CD3+CD4+ recovery was associated with age <18 years, non-malignant diseases, and lower incidence of acute graft-versus-host disease. CD34 dose <4 x 106/Kg had better CD3+CD4+ recovery compared with >4 x 106/Kg dose.

Conclusion: Our study revealed that factors like benign disorders, younger age and absence of aGVHD are associated with early IR, while older age, malignant diseases, major ABO-mismatch and non-sibling donors were associated with delayed IR.

Key Words:  Hematopoietic stem cell transplant, Immune reconstitution, Absolute lymphocyte count, Lymphocyte subsets, Graft versus host disease.