If the immune system perceives the HLA types as foreign, a reaction occurs.
Each person has two HLA haplotypes that allow human cells to be identified. Blood typing entails identifying these haplotypes (ABO compatibility). The closer the HLA types match, the greater the likelihood of identical antigens and the lower the chance of rejection.
What are Antigens?
Any substance that causes your immune system to produce antibodies against it is referred to as an antigen. This indicates that your immune system does not recognise the substance and is attempting to combat it. An antigen can be a natural substance such as chemicals, bacteria, viruses, or pollen.
Your body contains three types of antigen-presenting cells: macrophages, dendritic cells, and B cells. One of their jobs is to act as a detective, showing other immune system cells suspects they believe are invading your body.
When an antigen enters the body, it activates the adaptive immune system, which includes specialised immune cells such as B and T lymphocytes (B cells and T cells).
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