Ex Vivo Immunological Evaluation of Stable Mixed Chimeric Patients After Matched Related Donor Allogeneic Transplantation in Sickle Cell Disease

Cytotherapy. 2019 Dec;21(12):1206-1215. doi: 10.1016/j.jcyt.2019.10.003. Epub 2019 Nov 26.


Background aims: Allogeneic hematopoietic stem cell transplantation is curative for sickle cell disease, and the use of matched related donors, non-myeloablative conditioning and sirolimus immunosuppression results in stable mixed chimerism without graft-versus-host disease (GVHD). However, the time to terminate sirolimus while maintaining mixed chimerism is unclear.

Methods: In this study, we developed a two-way mixed lymphocyte reaction (MLR) to evaluate ex vivo immunoreaction in mixed chimeric patients.

Results: In co-culture of peripheral blood mononuclear cells (PBMCs) from two healthy controls (without irradiation), we detected proliferation at various ratios of PBMC mixtures (1:9 to 9:1) as well as various concentrations of sirolimus, suggesting that two-way MLR is applicable to patients (having >10% chimerism) undergoing sirolimus treatment. In two-way MLR using PBMCs (including donor and recipient cells) from mixed chimeric patients (n = 28), greater ex vivo proliferation was observed <6 months compared with >6 months post-transplant and healthy control PBMC monoculture. Robust ex vivo proliferation was observed in a patient with acute GVHD, and persistent ex vivo proliferation (until 2 years) was observed in a patient with decreasing donor chimerism.

Conclusions: In summary, we demonstrated that in two-way MLR, ex vivo immunoreaction decreases to low levels ~6 months post-transplant. These findings suggest a rationale to continue immunosuppression for 6 months.

Keywords: hematopoietic stem cell transplantation; matched related donor; mixed chimerism; mixed lymphocyte reaction; regulatory T cells; sickle cell disease; sirolimus.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Anemia, Sickle Cell / blood
  • Anemia, Sickle Cell / immunology
  • Anemia, Sickle Cell / therapy*
  • Blood Grouping and Crossmatching
  • Cells, Cultured
  • Female
  • Graft vs Host Disease / blood
  • Graft vs Host Disease / immunology
  • Hematopoietic Stem Cell Transplantation / methods
  • Humans
  • Immune Tolerance / immunology
  • Leukocytes, Mononuclear / pathology
  • Lymphocyte Culture Test, Mixed
  • Male
  • Middle Aged
  • Tissue Donors
  • Transplantation Chimera* / blood
  • Transplantation Chimera* / immunology
  • Transplantation Conditioning / methods
  • Transplantation, Homologous
  • Young Adult