HLA Typing & HLA Cross Match

HLA Typing & HLA Cross Match

HLA Typing or Tissue typing 

Every one knows about the blood groups “A”, “B” and “O”. These blood groups are specific markers on the red blood cells. 

Like blood groups, each of us has several other genetic markers located on the surface of most of our white cells. One particular group of genetic markers is called HLA or Human Leukocyte Antigens (leukocyte refers to white cell, and antigen refers to genetic marker). Half of these markers are inherited from the mother and half from the father. 

Tissue Typing is the name given to the test that identifies HLA of an individual . HLA typing is an essential part of the pre transplant work up. The number of antigens which are common between the donor and recipients HLA, determine the long term outcome of the graft and the chances of rejection. So that donor should be selected who have maximum match of HLA with that of the recipient. 

What is HLA cross match? 

After tissue typing is completed and a potential donor is selected having closest HLA matching with the recipient, there is a second test that will indicate if there is specific immune reactivity between the donor and recipient. This test is called as "crossmatch". 

The crossmatch is performed by mixing a very small amount of the patient serum with a very small amount of the potential donor white cells having donors HLA on their surface. This test detects the presence of any protein (Antibody) in the blood of the recipient against the HLA of the donor. 

If such an antibody is present, the white blood cells of the donor will be killed and the test will be called as “positive cross match”. A positive crossmatch is a contraindication to transplant, since it signifies that the patient has the ability to destroy the donor cells, and would, most likely destroy the donor implanted kidney. 

On the other hand a negative crossmatch indicates that the patient does not have the HLA antibody against that particular donor, and a transplant can be performed. Usually a patient can develop antibodies and positive cross match after a pregnancy, after blood transfusion or a prior transplant. 

Prerequisites for kidney transplant. 
Blood grouping and cross matching is the first step for kidney transplant workup. ABO compatibility and negative cross match between recipient and donor blood is the primary requirement for transplantation. 

Rh (Positve and Negative factor of the blood group) compatibility is not needed for the kidney transplant. Blood group “O” is a universal donor for all blood group recipients. 

For example a recipient having blood group “A +ve” or “A-ve” can get kidney from donors of blood groups of “A+ve”, “A-ve”, “O+ve” or “O-ve”, provided the blood crossmatch is negative.

Similarly recipients of blood group “B+ve” or “B-ve” can get kidney from donors of blood groups“B+ve”, “B-ve”, “O+ve” or “O-ve”.

Closest HLA matching between donor and recipient Negative HLA crossmatch.

There should be no donor contraindication for operation. There should be no recipient contraindication for the operation.