The genetic diversity at the HLA genes has resulted in the need for high-resolution tissue typing methods to ensure a full match. However, not all DNA changes are relevant for mounting the reactivity against the recipient and host cells. Therefore, we address the questions: (i) what is the functional relevance of an allelic mismatch and (ii) whether this translates into a new structure recognized by immune cells. This will aid us in identifying permissive and nonpermissive mismatches.

Recent publications suggest the association between polymorphisms in genes involved in cell trafficking and those influencing the pace and the regulation of the immune response and the risk of post-HSCT complications. In spite of this, no consistent recommendations have yet been made as to the practical use of this type of immunogenetic evaluation of donor-recipient pairs.

Bearing in mind that the patient should get the best possible donor, independently of a donor location, the international cooperation is mandatory. It is well recognized that the timing of donor acquisition is an important aspect of patient outcome. Therefore, all information on that as well as on the tools available to shorten the process is of practical value.

Independent of HLA matching status, the past history of the donor influences the ability of the transplanted cells to “see” too many or to neglect some epitopes. This raises the risk of alloreactivity in both the host and graft directions, as well as differencing potential to fight relapsing disease (graft versus leukemia reaction) or opportunistic infections. Such biological evaluations may focus on areas such as the pace of lymphocyte repopulation, tissue pathology, infectious complications, and relapse.

We are inviting all experts in this field to provide their opinions and data (patient outcome and biological/experimental) in any of these areas. Potential topics include, but are not limited to:

• HLA diversity recognition and its role in optimal matching in HSCT
• Specific alleles and mutations in genes encoding proteins involved in cell trafficking and the immune response associated with HSCT outcome including graft versus leukemia reaction
• Risk assessment associated with the “biological experience” of the donor immune system with regards to transplant outcomes and immune reconstitution
• Organization and international cooperation of voluntary donor and/or cord blood registries

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