H e m a t o lo g y E d u c a t io n - European Hematology Association

antigen. Cases can be encountered during the investigation
of a weak antigen. As exampled, it is frequent to
find the presence of both ceMO and ceAR, or both (C)ce S
and ceAR.
We have no response to the question whether these
heterozygous backgrounds in patients will prone allo
immunization with a clinically significant antibody.
Whether the expressed epitopes encoded by one allele
may compensate the missing epitopes of the antigen
encoded by the other variant (and vice versa) is not
known. One reason is probably that transfused patients
in this situation are rare. There is no data showing
DHTR in SCD with these types of backgrounds. Since
we do not know, and based also on our experience with
SCD transfusion, we do not share the idea that a molecular
compatibility should be performed for patients
with variants that have not been implicated in a DHTR.
This excess of precaution will introduce another high
risk for SCD patients: the absence of transfusion when
transfusion is the only option.
Conclusions
The relevance of variants in SCD has been demonstrated
for a few cases of molecular backgrounds. In all
other cases, even though the production of antibodies
has been associated with the presence of the variant in
the patient, there is no data on the clinical relevance of
these antibodies. A register on DHTR with involvement
of variants should be implemented. The point that
could be eventually relevant considering these variants
is the possibility that allo immunization to variants
could prone allo immunization to other significant antibodies,
frequently encountered in SCD DHTR, or to significant
auto antibodies. In case of such a demonstration,
it could be advice in some cases to consider variants
in the choice of the units. Studies are needed to
explore these hypotheses. In this prospect, molecular
biologists, immunologists, and serologists have to work
together. With the development of costly procedures to
type variants, it becomes a real issue to determine the
exact relevance of variants in the transfusion of SCD
patients.
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