Allograft Leukocyte Content and Post-Allogeneic Hematopoietic Cell Transplant Lymphopenia and Monocytopenia

BACKGROUND:  We have previously shown that lymphocyte and monocyte recovery by 2-3 months post-allogeneic hematopoietic (HCT) is associated with improved survival in recipients of both myeloablative and reduced intensity conditioning.  Here, we test the hypothesis that the allograft lymphocyte and monocyte content correlates with recovery of those hematologic parameters prior to and at day +100. 

METHODS: We pooled the hematologic recovery data, including absolute lymphocyte and monocyte counts (ALC and AMC, respectively) at day +15, +30, +60, and +100, and outcomes data from our original cohorts of allogeneic HCT recipients undergoing myeloablative or reduced intensity (fludarabine/melphalan).  We included only those with peripheral blood stem cell allografts and excluded those with incomplete data regarding allograft leukocyte subset content.  216 consecutive patients from 2000-2010 were included in the analysis. 

RESULTS: Neither allograft lymphocyte, monocyte, granulocyte, nor CD34+ content correlated with hematologic recovery parameters or overall survival in this cohort when cell doses were analyzed as continuous variables or divided in quartiles.  No overall prognostic or optimal pattern of allograft cellular content as determined by unsupervised hierarchical clustering could be identified.  With this pooled data, prognostic factors for overall survival based on multivariate analysis included severity of chronic GVHD (p<0.001), development of post-transplant relapse (p=0.001), day +60 AMC > 0.3 x 10⁹ cells/L (p=0.0015), and day +100 ALC > 0.3 x 10⁹ cells/L (p<0.001). 

CONCLUSIONS: We conclude that, unlike in the autologous HCT setting, post-allogeneic HCT lymphopenia and monocytopenia appear to be related to complications and treatment-related factors, and not related to allograft leukocyte content