HLA typing is one of the major laboratory tests performed to check for donor-recipient compatibility in transplantation. HLA typing involves the analysis of HLA polymorphism and is carried out by serological and genetic approaches.
The common serological method of HLA typing is based on a microlymphocytotoxicity test. Serological HLA typing is performed on isolated cell populations. A serological test determines the HLA type by examining which of the sera react with lymphocytes. Centrifugation or immunomagnetic separation is used to isolate the necessary cell populations from whole blood.
Molecular HLA typing methods use standardized synthetic samples that do not react with antigens on the surface of leukocytes, but directly indicate which antigens are present in the sample. Molecular genetic HLA typing commonly uses the PCR (polymerase chain reaction) method. Molecular HLA typing is more accurate and specific compared to the serological method.
HLA testing also includes a screening of antibodies that might target the donated tissues. HLA antibody testing is performed on the recipient to determine if they have antibodies that could attack the donated organ. Cell-based and solid-phase immunoassays are used to analyze if patients are sensitized to HLA antigens. The specificity of HLA antibodies, as well as the strength of reactivity, are determined using the technique.
Finally, lymphocyte crossmatching may be performed after the identification of the potential donor. The approach determines if the recipient has antibodies against antigens located on the donor's lymphocytes. Any reaction between recipient serum and white blood cells of donor detected would indicate incompatibility..