Impact of clinical factors and allograft leukocyte content on post-transplant lymphopenia, monocytopenia, and survival in patients undergoing allogeneic peripheral blood haematopoietic cell transplant

BACKGROUND: We have previously shown that lymphopenia and monocytopenia at 2–3 months post-allogeneic haematopoietic cell transplant (HCT) is associated with poor survival in recipients of both myeloablative and reduced intensity conditioning regimens. It is not known whether the graft leukocyte content has a role in early lymphocyte and monocyte recovery following allogeneic T-cell replete peripheral blood HCT. METHODS: Haematologic recovery data, including absolute lymphocyte and monocyte counts (ALC and AMC, respectively) at day +15, +30, +60, and +100, and outcomes data were pooled from two prior independent cohorts, and parameters were correlated with leukocyte graft content in those individuals receiving peripheral blood progenitor cell grafts. 216 consecutive patients from 2001–2010 were included in the analysis. RESULTS: Neither infused allograft lymphocyte, monocyte, granulocyte, nor CD34+ cell number per kilogram recipient body weight correlated with haematologic recovery parameters or overall survival in this cohort. Prognostic factors for overall survival based on multivariate analysis were as expected from the results of the previous independent cohorts and included severity of chronic GVHD (p < 0.001), development of post-transplant relapse (p = 0.001), day +60 AMC > 0.3 x 10(9) cells/L (p = 0.0015), and day +100 ALC > 0.3 x 10(9) cells/L (p < 0.001). Low monocyte and lymphocyte counts at the day +60 and day +100 time points were significantly associated with acute GVHD and/or CMV viraemia. CONCLUSIONS: This study suggests that graft cell count does not influence post-transplant monocyte and lymphocyte recovery following T-cell replete allogeneic peripheral blood HCT. Post-transplant complications such as acute GVHD and/or CMV viraemia negatively influenced monocyte and lymphocyte recovery, and hence the survival. Further studies aimed at understanding the mechanisms behind sustained lymphopenia and monocytopenia post-transplant are needed.