Pre-transplant bone marrow lymphocyte subsets predict outcome after allogeneic stem cell transplantation

Recent evidence has demonstrated that both donor- and recipient-derived immune cell subpopulations play a crucial role in various immune responses following allogeneic hematopoietic stem cell transplantation (HSCT). In this retrospective single center analysis, we investigated whether different lymphocyte subpopulations in the bone marrow (BM) of the recipient prior to HSCT might have an impact on outcome parameters after HSCT.

BM aspirates of 140 patients > 18 years of age receiving a HSCT between 2008 and 2022 were analyzed. BM aspiration was performed within 3 months prior to HSCT. Median time from aspiration to HSCT was 14 days (range 8-104 days). Lymphocyte subpopulations included CD19⁺ B cells, CD56⁺ NK cells, CD3⁺ T cells, CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD3⁺CD4^-CD8^- T cells and CD3⁺CD4⁺CD8⁺ T cells.

High total lymphocytes > 37.35% (of leukocytes) correlated with an increased non-relapse mortality (NRM) at day 100 after HSCT, whereas high CD3⁺ T cells > 69.45% (of lymphocytes) and CD3⁺CD8⁺ T cells > 46.3% were associated with an increased risk for CMV infection. High NK cells > 8.8% resulted in an increased incidence for acute graft-versus host disease (GvHD). High CD19⁺ B cells > 13.1% resulted in a decreased incidence of chronic GvHD. In contrast, high CD4⁺ T cells > 49.3% were associated with an increased incidence of chronic GvHD.

Recipient-derived lymphocyte subpopulations within the BM prior to HSCT comprise the prognostic potential to assess post-HSCT related outcome parameters. In summary, a shift towards humoral immunity with a BM characterized by a B cell enriched and T cell/NK cell depleted microenvironment appears to be associated with a lower risk for post-HSCT complications.