Transplantation can learn from egg cell donation

A pregnancy resulting from egg cell donation is in fact a form of transplantation; after all, it also involves a foreign element. And yet the odds of it being rejected are far smaller than in the case of organ transplantation. Why? This is the question Marie-Louise van der Hoorn asked in her PhD defence.

Placentas

Van der Hoorn collected placentas from egg cell donation pregnancies and spontaneous pregnancies. She then demonstrated the presence in both types of placenta of particular cytokines (proteins which play a role in the immune system), and compared their numbers.

Different HLA types

Another factor that played an important role in the study was HLA, the Human Leukocyte Antigen, an antigen that can provoke an immune reaction. It is present in all body cells, with the exception of red blood cells. Unrelated individuals generally have different HLA types, which is the reason that the body tries to reject a foreign organ (HLA mismatch). In the case of organ transplantation, drugs are required to inhibit this rejection reaction. Van der Hoorn collected maternal blood and umbilical cord blood in order to calculate the number of HLA mismatches. In addition, certain types of immune cells (T-cells) were identified in the maternal blood.

Different forms of immune regulation

In her placenta study, Van der Hoorn related the HLA mismatches to the number of active immune cells. She came to the conclusion that the immune regulation in egg cell donation pregnancies works differently from that of spontaneous pregnancies. The differences can be found in the maternal blood, in the placenta and in the reactions between foetal and maternal cells.

More active immune cells

Van der Hoorn discovered that if there are more HLA mismatches in the egg cell donation pregnancies, the maternal blood also contains more active immune cells. In other words: if the genetic differences between mother and child are greater, as is the case in egg cell donation pregnancies, another mechanism is active that ensures that the foreign pregnancy is accepted.

Last Modified: 18-01-2012