HLA and Tissue Typing Flashcards
What does HLA stand for?
Human Leucocyte Antigens
What is the role of HLA?
Determines if something ‘belongs’ to the body or not.
How many classical loci of HLA are there?
- Class I (A,B,C) and Class II (DR, DQ, DP)
What are the Class I HLA loci?
A, B ,C
What are the Class II HLA loci?
DR, DQ, DP
What is the purpose of loci molecules in HLA?
Allow tissue to be recognised as ‘self’ or ‘non self’ by host immune system to determine histocompatibility.
What chromosome is HLA found on?
Chromosome 6
Where is the HLA region located on chromosome 6?
On the short arm
Which HLA class are expressed on almost ALL cells?
HLA Class I
Which HLA class recognise intracellular pathogens?
HLA Class I
Which HLA class are found on immune cells?
HLA Class II
Which HLA Class recognise extracellular pathogens?
HLA Class II
How are HLA very Polymorphic?
They have many different alleles. Serve to recognise and initiate an immune response.
Which HLA Class are expressed on all nucleated cells?
HLA Class I
Which HLA Class are expressed on antigen-presenting cells?
HLA Class II
What does HLA-A define on nomenclature?
The locus
What does HLA-A24 show on nomenclature?
The antigen has been serologically defined
What does the asterisk in ‘HLA-A*24’ show?
This shows that the allele was defined through low resolution molecular methods.
What does the ‘:’ in HLA-*24:01 show?
This shows a specific allele from a higher resolution.
How many antigens and alleles does HLA A have?
28 antigens. 1729 alleles.
How many antigens and alleles does HLA B have?
60 antigens. 2329 alleles.
How many antigens and alleles does HLA C have?
10 antigens. 1291 alleles.
How many antigens and alleles does HLA DR have?
21 antigens. 1051 alleles.
How many antigens and alleles does HLA DQ have?
9 antigens. 160 alleles.
How many antigens and alleles does HLA DP have?
6 antigens. 150 alleles.
What percentage of England have HLA type A*24?
10.5%
What is the percentage of HLA A*24 in Columbia?
26.2%
What is significant about HLA B46?
This is 0% in most countries but 29% in Thailand. (10% in Japan)
Who MUST have their HLA loci determined?
All potential organ recipients and donors so that rejection is minimised.
What are Terasaki trays?
Plates used in HLA serology that contain serum with anti-HLA antibodies. A patients cells and complement are added and if the antibody reacts with patients sample then death occurs.
What does the green dye show in a terasaki tray?
Live cells
What does red dye show in terasaki trays?
Dead cells.
What do ALL molecular methods of HLA typing require?
Require the extraction of high quality genomic DNA.
What is used by NHS labs to carry out molecular HLA typing?
A semi-automated system that extracts genomic DNA from whole blood.
Where else can genomic DNA be isolated from for HLA molecular typing?
Buccal swabs, Saliva samples, Fingernails.
What is an SSP in molecular HLA typing?
Sequence Specific Primer (SSP). Often the first step.
What is often the first step in HLA molecular determination?
SSP.
What does a Sequence Specific Primer consist of?
Multiple PCR primers that are specific to known HLA polymorphisms (antigens/alleles). These are supplied in a kit.
What does a SSP produce?
Specific amplicons are produced from PCR if the primers are complimentary to sample patient DNA.
How many people have HLA-B27?
8%
What are risks associated with HLA-B27?
Risk of ankylosing spondylitis (spinal inflammation) and other inflammatory disorders.
What percentage of Ankylosing Spondylitis sufferres are HLA-B27 positive?
95%
What disorder is associated with HLA-B57?
Drug induced inflammatory disorder.
What two HLA types are patients screened for prior to UK treatment?
HLA-B27. HLA-B57.
What is a major risk factor associated with hyperacute rejection?
Recipients may have antibodies to antigens that are expressed on donor cells.
Where might anti-HLA antibodies develop from?
Pregnancy. Blood transfusion. Previous transplantation.
What is a CDC crossmatch? When is it done?
Carried out right before surgery. Recipient sera is incubated with donor lymphocytes in the presence oof complement.
What does CDC stand for?
Complement Dependent Cytotoxicity