Immune Reconstitution Following Allogeneic HSCT in Hematological Diseases

Objective: To evaluate immune reconstitution following allogeneic hematopoietic stem cell transplantation

Study Design: Retrospective cohort study

Place and Duration of the Study: Department of Bone Marrow Transplant, Quaid-e-Azam International Hospital Islamabad, Pakistan; from January 2023 to January 2024.

Methodology: We evaluated 50 adult and pediatric patients undergoing allogeneic HSCT for malignant and nonmalignant diseases from year 2022 to 2023. Absolute lymphocyte count, lymphocyte subsets and immunoglobulin levels were performed at 6 and 12 months post-transplant. Patients who did not have complete medical records or faced graft failure/rejection before 6 months post-transplant were excluded from the study.

Results:

In our study absolute lymphocyte count recovery was observed in 94% of patients on D+180 that increased to 100% on D+365. The average number of cells being 2599.84/μL (SD=1281.742) and 2926.96 μL (SD=1065.378) on D+180 and D+365 respectively. By day 180 post-transplant, 84% of patients had achieved CD3+CD8+ recovery, while CD16+CD56+ and CD19+ cell recovery was seen in 74% and 56% cases respectively. Day +180 CD3+CD4+ recovery was seen in only 8% patients that increased to 21% by day +365. Normal lymphocyte recovery values at day 365 post-transplant were: CD3+CD8+ in 84% patients, CD16+CD56+ and CD19+ cells in 78% patients. Early CD3+CD4+ recovery was seen in patients with age <18 years, non-malignant diseases and with no or minimal GVHD but the values were not statistically significant. Age adjusted normal immunoglobulin levels for IgG, IgM and IgA by day +180 were achieved in 92%, 90% and 84% patients while after 1 year 98%, 90% and 96% patients had normal levels of IgG, IgM and IgA respectively. Patients receiving CD34+ dose >5 x 10⁶/kg had significantly early neutrophil engraftment (p=0.025); mean 11.40 days (SD 1.67) versus 13.76 days (SD 1.43) for CD34 dose ≤ 5 x 10⁶/kg.

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Conclusion: Majority of the patients achieved normal immunoglobulin levels and lymphocyte subsets by day 180 post HSCT while CD3+CD8+ T cell recovery was seen in 8% and 21% patient by day 180 and 365 post-transplant, respectively.

Key Words: Hematopoietic stem cell transplant, lymphocyte subsets, immune reconstitution

No relevant conflicts of interest to declare.