Rapid Increase of CD8+ T Cell Count in Peripheral Blood of Pediatric Patients After HLA-Identical Stem Cell Transplantation for African Sickle Cell Anemia

Sickle Cell anemia (SCA) remain a disease with high risk of morbidity and early death, especially in African patients. Allogeneic haematopoietic stem cell transplantation (HSCT) is the only curative treatment for SCA. To analyze immunohematological reconstitution after transplant, we report our experience concerning 12 geno-identical HSCT for SCA-patients prepared with the same myeloablative conditioning regiment consisting of Busulfan and Cyclophosphamide.

Twelve patients with a median age of 12 years (range, 2–16), affected by sickle cell anemia (SCA), received hematopoietic stem cell transplantations from HLA-identical, related donors following a myeloablative conditioning regimen. To analyze the mechanisms involved in immunological reconstitution post transplant, we analyzed T cell subsets by flow cytometry at + 60 post transplant.

All patients had sustained engraftment and remained free of any SCA-related events after transplantation. Sixty days after the transplant, the patients had significantly lower CD4+ T cells in comparison to the controls (15.6 ± 5.9 % vs. 47.5 ± 6% respectively), whereas CD8+ T cells were the first lymphocytes to repopulate the peripheral blood with up to 45% of these cells being CD8+ T cells (in mean 48.5 ± 14.3 % vs. 20 ± 7%). All patients displayed reduced numbers of B cells versus normal value, and 10/12 patients had only 0% to 1% of control levels of CD19+ cells. CD3-CD56+^bright NK cells were 18.6 ± 12.2 %, whereas CD3-CD16+ (with cytotoxic functions) were 16.7 ± 11.8 %.

Our primary finding include the following: 1) rapid increase of lymphocytes in peripheral blood after transplant; 2) rapid expansion of CD8+ T cell but not CD4 T cell counts. Probably reactivation of cytomegalovirus (CMV) infection, observed in 11/12 patients on the early stages of T-lymphocyte recovery after transplant, might induce a dramatic increase in CD8 but not in CD4 T-cell counts.

No relevant conflicts of interest to declare.