HLA typing resolution. The Venn diagram illustrates increasing levels of HLA typing resolution. The figure on the left shows the antigen binding site of an HLA class I molecule. High-resolution HLA typing defines the specific DNA sequence of the antigen binding site. Allelic resolution defines a single allele as defined by a unique DNA sequence for the HLA gene; in certain instances, the allele name may include synonymous DNA substitutions within the coding region, differences in the noncoding region, and changes in expression. An example of allelic resolution is A*01:01:01:01 for which synonymous DNA substitutions and differences in the noncoding region have been defined. A*02:07 is also an example of allelic resolution; this allele has not been found to have synonymous DNA substitutions or differences in the noncoding region to date.