Remove allele_id property.  (If needed, a CodeSystem supplement could define it.  Defining a separate allele_id CodeSystem, and related ConceptMap, may also be a reasonable option.)  Trying to keep the list of concept properties as straightforward as possible for now.
@@ -139,12 +139,6 @@ Tissue Antigens (2000), 55:280-287
<!--
IMGTHLA concept properties.
-->
- <property>
- <code value="allele_id"/>
- <uri value="http://www.ebi.ac.uk/ipd/imgt/hla/property/allele_id"/>
- <description value="IPD-IMGT/HLA database accession number."/>
- <type value="string"/>
- </property>
<property>
<code value="expression_suffix"/>
<uri value="http://www.ebi.ac.uk/ipd/imgt/hla/property/expression_suffix"/>
