ABO incompatibility may be a significant prognostic risk factor after allogeneic bone marrow transplantation in susceptible subgroups of recipients. Care is necessary to design hematopoietic stem and progenitor cell-processing and -transfusion policies to minimize this risk.

Liquid nitrogen freezers are not sterile, and both the liquid and vapor phases are potential sources of microbial contamination of HPC components. While low-level contamination by environmental organisms may be common, the occurrence of heavy contamination by potential pathogens such as Aspergillus species suggests that monitoring of liquid nitrogen sterility may be indicated. Strategies to assess and prevent microbial transmission from liquid nitrogen to HPC components need further development.