Pregnancy and HLA Antigens

HLA Antigens:

HLA or Human Leukocyte Antigens exist as proteins in the body in various forms.  Some are only in blood cells. Others are in all the different tissues of the body. These proteins’ main work is to reject tissue transplanted from one individual to another as a protection to the body.


Antibodies are proteins in the blood that can specifically recognize and bind tightly to other proteins/substances.  When that happens, a series of reactions begins that eliminate the recognized substance.  If that substance is a normal part of a tissue or organ in the body, then damage can occur to that tissue or organ, and it can be harmful. 

Anti-HLA Antibodies:

Antibodies against HLA antigens may form after an organ transplant, a blood transfusion or a pregnancy.  They do not cause any harm to the body of the person making them and the person is not ill because of having them.  Anti-HLA antibodies produced in the body after pregnancy usually have no effect on the woman or on her subsequent pregnancies.

However, if present in blood given to a person, those antibodies can be life-threatening.  In rare instances, a condition called Transfusion-Related Acute Lung Injury (TRALI) can occur.  The likelihood of this harmful reaction depends on the specific antibodies and amount of antibodies in the donor’s blood.  The types of the HLA proteins in the person receiving the blood, the amount of blood transfused and the size of the recipient are all factors as well. 

Read more about Transfusion-Related Acute Lung Injury (TRALI) in this article published in Critical Care Medicine in 2008.

Bob Grant