Tissue typing

As part of Immunology at Derriford we run a 24hr on-call service for transplantation. All renal patients in the SW transplant centre are tissue typed in the lab and their bloods regularly monitored for the production of HLA specific antibodies (usually occurring as a result of transplantation, blood transfusion or pregnancy). Potential live kidney donors are also typed in the lab, followed by pre-transplant crossmatching of the most suitable recipients with donor tissue.

Patients being worked up for entry onto the transplant waiting list should have bloods sent to Immunology. Tissue typing is performed on patient DNA using the Polymerase Chain Reaction (PCR) technique and 4 EDTA tubes (purple top) should be sent for this purpose. HLA antibodies are detected using panels of known HLA types by flow cytometric, ELISA and lymphocytotoxic methods, and a further clotted sample (red top) must be sent for this purpose.

Patients’ HLA antibody status (quoted as panel reactive antibodies or PRA) is subject to vary due to the factors listed above, but infection can also stimulate an increase in HLA antibody produced by a previous immunising event. For this reason we ask for a clotted sample to be sent every month on all patients being worked up for, and whilst on the transplant waiting list. Please also ensure a clotted sample is sent 10-14 days after any known sensitising event (e.g. blood transfusion), with details.

Deceased donors may originate within the SW transplant region, or from national donors. Local donors will be tissue typed in the lab using both PCR and lymphocytotoxic methods and the results transmitted to UK transplant in Bristol, who will perform a ‘matching run’. 4 EDTA, 4 citrates and a clotted tube should be sent for this purpose.

If the donor is heart-beating the organs will be offered to the best matched recipients nationally, if the donor is non-heart beating then the kidneys will be used for the most suitable recipients on the SW transplant waiting list, and these patients will be called to the unit.

If the kidneys are to be transplanted locally, then following donor nephrectomy a sample of donor tissue (usually spleen but may be lymph nodes) is sent to the lab and a pre-transplant crossmatch against the potential recipient is performed using fresh serum and stored serum from that patient when their panel reactive antibodies, if any, were at their highest (peak PRA). The transplant cannot proceed unless the crossmatch is negative.

Finally, patient serum is stored from the first few days post transplant, monthly for the first 3 months, 3 monthly for the first year and annually thereafter. Please ensure a clearly labelled clotted sample is sent to the lab around these times and at any suspected rejection episode.

These procedures are in accordance with the British Transplant Society guidelines.