HLA Full Form

Human Leukocyte Antigen is a complex that is located on the plane of maximum cells in an individual’s body. In the immune system of a person, Human Leukocyte Antigens contribute a vital function as a response to foreign substances. HLA builds up tissue types of a person that varies in individuals. Testing of Human Leukocyte Antigen is performed before the organ transplantation of donor, this test is done to match the similarity of tissues of donor with the tissues of the receiver. The cell-surface proteins are encoded by the Human Leukocyte Antigen (HLA) genes, which are a segment of the Major Histocompatibility Complex. 

Human Leukocyte Antigen 

Before knowing about HLA i.e. Human Leukocyte Antigen, one needs to know about MHC i.e. Major Histocompatibility Complex (MHC). The term Histocompatibility refers to the quality of tissue being compatible. This term is used in transplantation to describe the ability of a donor’s organ or tissue to be accepted by the recipient. In humans, MHC is simply called Human Leukocyte Antigen (HLA). HLA is the human form of MHC and these are the proteins situated on the surface of white blood cells (WBC) and other tissues of the body. The Human Leukocyte Antigen is the vital segment of the immune system; HLA is being controlled by more than 200 genes that are situated on chromosome 6. Human Leukocyte Antigen genes are segregated into 3 groups – Class I, Class II, and Class III. Some Human Leukocyte Antigen (HLA) genes are related to human diseases like cancer and autoimmune disorder such as celiac disease and type I diabetes. Human Leukocyte Antigens are largely polymorphic which exhibits that they are consists of various alleles, which fine-tunes the immune system. Human Leukocyte Antigen is vital in defeating diseases. A patient who is going through the process of stem cell transplantation, Human Leukocyte Antigen sensitization may be a trouble for them. In the immune system HLA class, I am there in intercellular peptides to cytotoxic T-cells and is also present on every nucleated surface of the cell. HLA has a major contribution to cellular immunity, which can be particularly seen in transplant reactions. Two antibodies that can bind complement are anti-HLA-DQ and anti-HLA-B. In transplant-mediated rejection, HLA antigens play a remarkable role that is considered under the following categories:

• T-cell-mediated Rejection –

In the T-cell-mediated rejection, due to the interaction between the HLA-peptide and T-cell receptor combination, the activation of the T-cell occurs. 

• Antibody-mediated Rejection –

After the organ transplantation in a patient graft loss occurs due to the Antibody-Mediated Rejection (AMR) and is known as a vital cause of graft loss. This happens due to the anti-donor-specific antibodies mainly anti-HLA antibodies. The phenotype of Antibody-Mediated Rejection ranges from acute AMR, chronic AMR, and hyperacute rejection. The diagnosis of Antibody-Mediated Rejection relies on typical C4d staining, serum DSA detection, and histological lesions. C4d is considered a marker of diagnosis for Antibody-mediated Rejection.

The function of Human Leukocyte Antigen

The important functions of HLA (Human Leukocyte Antigen molecule) are the Immune system’s regulation, selection of T-cell repertoire, and the process of induction. By the combination of HLA, molecules T-cells can recognize the foreign antigens. 

HLA Testing

HLA Testing or Human Leukocyte Antigen Testing is done before planned transplantation, this can be done in both donor and recipient. This testing is also performed for identifying HLA antigen types in the donor who donated platelet blood that matches with the transfusion recipients. The HLA Testing is mainly done when the transplantation occurs for a solid organ i.e. when a solid organ is transplanted or Hematopoietic Stem Cell (HSC) transplantation. Before transplantation, this type of testing is done. The sample that is required for the Human Leukocyte Antigen testing is a blood sample from the vein of the receiver or donor tested. There is also another method that is performed during the HLA typing i.e. by taking a swab from the mouth (wall of cheek).

Conclusion

It is to be concluded that Human Leukocyte Antigens are special proteins that are found on the outer wall of all the cells in individuals, except the cells that are present in red blood. The HLA (Human Leukocyte Antigens) genes are placed in the area of chromosome 6 which is known as MHC (Major Histocompatibility Complex). For managing and maintaining the immune system of a person MHC plays a vital role.