|MadSci Network: Immunology|
The antibodies are made by your immune cells against the bacterial antigens that resemble the blood group antigens. So why don't your own immune cells produce antibodies against your own blood type?
Your question is a good one and was a mystery to immunologists for some time. However, we now know that there are several mechanisms by which the developing fetus eliminates or inactivates immunocytes that might react against self tissues. These mechanisms are called "clonal deletion" (elimination of self-reactive clones), "clonal anergy" (the functional inactivation of self-reactive clones induced by antigen), and "clonal suppression" (the functional inactivation of self-reactive clones induced by other cells of the immune system). During development, immune cells, such as B cells (which produce antibodies) and T cells (which "help" B cells or attack abnormal cells) which react against self antigen are either eliminated from the body or cause to be anergic (unresponsive). Therefore, our cells do not react to self tissue and antigens.
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