The helper T lymphocyte precursor (HTLp) frequency does not predict outcome after HLA-identical sibling donor G-CSF-mobilised peripheral blood stem cell transplantation

Here, we report the first study assessing the helper T lymphocyte precursor (HTLp) frequency as a predictor of outcome in patients undergoing allogeneic PBSC transplantation. The HTLp assay uses limiting dilution analysis to measure the frequency, in PBMCs from the donor, of T lymphocytes capable of producing IL-2 in response to histocompatibility antigenic differences on PBMCs from the recipient. This assay has shown promise as a functional histocompatibility assessment used to predict the risk of recipients of HLA-matched donor bone marrow developing severe acute GVHD: the higher the HTLp frequency, the greater the significance of any histoincompatibility, and the greater the risk of severe acute GVHD. In the current report, the HTLp frequency was measured in 28 HLA-identical sibling pairs who subsequently underwent allogeneic PBSC transplantation for haematological malignancies. The HTLp frequency did not predict for acute GVHD (P = 0.38), chronic GVHD (P = 0.95), transplant-related mortality (P = 0.79), relapse (P = 0.39) or overall survival (P = 0.84). Converting the HTLp frequency to HTLp infused per kilogram of recipient body weight also did not predict for any of the outcome measures. We conclude that, although the HTLp assay may be useful for patients undergoing BMT, it does not predict for outcome after HLA-identical sibling donor G-CSF-mobilised PBSC transplantation.