Study Offers Hints on the Reason Pregnancy May Raise Danger of Rejection of Organ Transplant

A University of Chicago study has recently found that during pregnancy, while the T cell reaction to a fetus turns out to be tolerant to allow for a successful pregnancy, a portion of the immune system that produces the humoral response known as the antibodies becomes sensitized, developing memory B cells that can later help in rejecting an organ transplant.

According to News-Medical.Net, the study's findings, which were published yesterday in the Journal of Clinical Investigation, help clarify why the immune system can endure a fetus during pregnancy, although later may be more likely to become alerted to and reject a transplant of an organ.

The immune system is designed to react to and shield from foreign invaders. It does this by acknowledging molecules on foreign cells identified as antigens and intensifying an immune response that generates T cells to aim and directly attack foreign cells and memory B cells that yield antibodies to identify foreign cells for damage by other blood cells.

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Increased Risk of Rejection 

In most circumstances, the said system exceptionally beneficial, although during pregnancy, some adaptation is needed to avoid the rejection of a fetus, which only shares 50 percent of its genes with the mother and thus exhibits foreign antigens to the immune system of the mother.

This has an inconsistent effect, increasing the risk of rejection for a transplanted organ after a mother has given birth, specifically if the transplanted organ, like the kidney, is from their children's father.

This new stud was essentially inspired by previous work, presenting that T cells are becoming tolerized during pregnancy. Meaning, they are not responsive to fetal antigens.

This new research was inspired by prior work showing that T cells become tolerated during pregnancy, meaning they don't respond to fetal antigens.

According to UChicago's surgery professor, Anita Chong, Ph.D., the co-senior author of the study, "This was paradoxical to the transplant field," where pregnancy is considered a sensitizing event.

Chong also said she wanted to know the reason it was that pregnancy that led to sensitization to a transplanted organ also called the "allograft" from a male partner, but improved tolerance to a fetus, conveying the same antigens.

Immune Response Studied

In the said research, the study authors evaluated female rats' immune reactions following receipt of a "transplanted heart from one of their offspring."

 By following both the T cell response and the humoral response, they could track both arms of the immune response and investigate their impacts on the rejection of transplants.

The investigator saw, too, that the T cells did not respond to the organ transplant, although the memory B cells did, generating antibodies against foreign antigens from the heart transplant.

Chong explained that pregnancy could not progress to totally remove the humoral reaction as it is crucial for a mother to yield antibodies contrary to contagious pathogens during pregnancy and breastfeeding.

This is the only immunity a mother can transfer to her child. Therefore, the immune system is geared up to make antibodies to counter anything unusual during this period, which includes those conveyed by the fetus, elaborated Chong.

Consequently, the placenta has evolved ways to manage such antibodies to avoid rejection of fetus in succeeding pregnancies. Such findings are a promising start for the prevention of transplant rejection in people after pregnancies later on.

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