CPT® Code 86821

Human leukocyte antigen (HLA) typing is a critical laboratory procedure that identifies specific HLA alleles in individuals. This process is essential for assessing tissue compatibility, particularly in the context of organ transplantation, such as stem cell, bone marrow, or solid organ transplants. The HLA system is categorized into Class I and Class II major histocompatibility alleles, which play a significant role in the immune response. The mixed lymphocyte culture (MLC) technique is employed in HLA typing, where genetically distinct lymphocyte populations are combined to evaluate their interactions. This method involves using cells that are homozygous for specific HLA antigens as stimulators and purified lymphocytes from the blood, thymus, lymph nodes, or spleen as responders. By measuring the cellular proliferation or response of the test cells when mixed with the stimulator cells, healthcare professionals can determine compatibility. A positive response indicates that the responder cells are not compatible with the stimulator cells, while a lack of response suggests compatibility. This testing is vital for ensuring successful transplant outcomes and minimizing the risk of transplant rejection.