Histocompatibility and immunogenetics

Anthony Nolan’s laboratories, led by Dr Katy Latham, BSc PhD, FRCPath, Laboratory Director and Senior Research Scientist, provide a Histocompatibility and Immunogenetics service, testing the HLA type of donors joining the Anthony Nolan register and potential recipients.

We also work for haematopoietic stem cell transplant centres throughout the world.

Why do donors and recipients need to have matching HLA types?

A person’s human leukocyte antigen (HLA) type is like a barcode on the immune system’s cells. It allows the body to determine self from non-self so it can fight invading organisms.

This barcode plays such a critical role in human defences that each individual has developed their own almost unique one. So it can’t be compromised. 

Unfortunately this makes transplantation difficult. Unless a donor has essentially the same HLA barcode as a recipient, the donor cells can attack the body, or the recipient’s cells can attack the donor's cells.

For successful stem cell transplants, we need to find donors with the same HLA type. And for this we need a very large pool of donors to select from.

How do you do HLA typing?

HLA is a group of highly polymorphic genes in a region called the major histocompatibility complex, found on chromosome six.

HLA typing involves identifying these gene products.  We analyse the DNA sequence of each gene, which allows us to define specific alleles and determine a person’s HLA type.

DNA can come from a blood sample, buccal swab or saliva.

The first step: polymerase chain reaction

The first step in the HLA typing process is a procedure called the polymerase chain reaction (PCR). PCR essentially acts as a DNA photocopier, making billions of copies of the specific genes we are trying to determine. This allows us to use a number of techniques to study the gene products further.

After PCR, we use three main methods for HLA typing:

1. Sequence specific oligonucleotides (SSOP)

Our SSOP protocols use Luminex xMAP® technology, where oligonucleotide probes are individually attached to up to 100 sets of uniquely fluorescent microspheres. This allows 100 different reactions to be measured in a single tube.

This methodology is very appropriate for the HLA typing of large numbers of samples. We use it as our primary tissue typing technique for all donors and patients.

1. Sequence specific primers (SSP)

We use PCR to check whether a specific DNA sequence is present in the HLA gene.

This can be used to undertake final stage testing of patients and donors to high resolution. Due to its speed, it can also be used to obtain HLA typing of potential donors for solid organ transplantation.

1. Sequence based typing (SBT)

We directly analyse the DNA sequence of the area of interest, performing nucleotide sequence analysis of the PCR product. We use this method to achieve high resolution results for final stage testing of patients and donors and to also resolve any novel results.

The Histocompatibility laboratories rely heavily on liquid handling systems to help process the high throughput of samples we receive each day. We have robotic systems for DNA extraction, virology screening, PCR setup and the SSOP processes. 

How many people work in the laboratories?

We have 60 scientific, technical and administrative staff working in our laboratories.

The Histocompatibility laboratories have six main departments:

• The Cellular team is responsible for sample receipt, DNA extraction, serological HLA typing, ABO blood grouping and virology screening.
   
• The Intermediate Typing team performs all the SSOP typing and is responsible for HLA typing all new potential donors being added to our register.
   
• The High Resolution team perform the high resolution typing required for the exact matching of donor to patient at the final stages of the matching process.
   
• The Clinical Services team provide scientific support for the transplant centres that use our HLA typing service.
   
• The Solid Organ team provide scientific support for the Royal Free Hospital’s renal, liver and islet cell transplants.
   
• The Registry Reporting team coordinates the processing of samples for disease association testing and Anthony Nolan cord blood. It also works closely with the Registry Development team.

Our laboratories are accredited by Clinical Pathology Accreditation (UK) Ltd, the European Federation for Immunogenetics, the Human Tissue Authority and the Care Quality Commission.