[The Effect of Haplo-Cord Mixed Chimerism on Lymphocyte Subsets in Aplastic Anemia after Haplo-Cord HSCT]

To explore the changes and clinical significance of lymphocyte subsets in peripheral blood of aplastic anemia (AA) pediatric patients with mixed chimerism of dual donors.

Twenty-five pediatric patients with AA who underwent a haploidentical stem cells combined with umbilical cord blood transplantation (haplo-cord HSCT) in Children's Hospital of Soochow University from March 2020 to April 2023 were included. The changes in chimerism and lymphocyte subgroup levels after transplantation were observed. The differences in lymphocyte subgroups between haploid chimeric and double donor chimeric pediatric patients were compared.

After haplo-cord HSCT, the absolute count of NK cells in the 25 pediatric patients recovered and reached reference levels within as early as 3 months, the absolute count of CD8 ⁺ T cells reconstituted more rapidly compared to CD4 ⁺ T cells, while B cells hadn't reached reference level after 12 months. Among the 25 pediatric patients, 5 cases (20%) showed haplo-cord mixed chimerism and others were haploidentical chimerism. In the haploidentical chimerism group, the absolute count of B cells had significantly lower levels at 6 and 12 months after transplantation compared to the haplo-cord mixed chimerism group (both P < 0.05), and the absolute count of NK cell was significantly lower at 6 months after transplantation (P < 0.01).

After haplo-cord HSCT, NK cells reconstitution is the fastest, while B cells reconstitution is the slowest. B cells reconstitute in the haplo-cord mixed chimerism group is faster compared to the haploidentical chimerism group.