Editing Histocompatibility (section)

== Testing ==
Because of the clinical significance of histocompatibility in tissue transplants, several methods of typing are used to check for HLA allele expression.

=== Serological Typing ===
Serological typing involves incubating lymphocytes from the recipient with serum containing known antibodies against the varying HLA alleles. If the serum contains an antibody specific for a HLA allele that is present on the recipient's lymphocyte, the antibodies will bind to the cell and activate a [[Complement system|complement]] signaling cascade resulting in cell lysis. A lysed cell will take up an added dye such as [[trypan blue]] allowing for identification. Comparing which serums triggers cell lysis allows identification of HLA alleles present on the cell surface of the recipients cells.<ref name="Chandraker_2012">{{cite book |  first1 = Anil | last1 = Chandraker | first2 = Mohamed H. | last2 = Sayegh | name-list-style = vanc |title=Core concepts in renal transplantation|date=2012|publisher=Springer Science+Business Media, LLC | pages = 1960 |isbn=9781461400073|location=New York|oclc=768245800}}</ref>

Serological typing has the benefit of quickly identifying expressed HLA alleles, and ignores any non-expressed alleles that could be of little immunological significance. However, it does not recognize subclasses of alleles, which are sometimes necessary for matching.<ref name="Chandraker_2012" />

=== Molecular Typing ===
HLA alleles can be determined by directly analyzing the HLA loci on chromosome 6. Sequence specific oligonucleotide probes, sequence specific primer [[Polymerase chain reaction|PCR]] amplification, and direct sequencing can all be used to identify HLA alleles, often providing amino acid level resolution. Molecular methods can more accurately identify rare and unique alleles, but do not provide information about expression levels.<ref name="Chandraker_2012" />