Numerous factors are involved in making the amazing miracle of pregnancy possible. Many of them are very well understood whilst others, such as the immune system and its role in embryo implantation, given their importance, are still being studied and researched in depth. If the immune system is what protects the body against infection and diseases thanks to its defences, what role does it play in achieving pregnancy?
Experts in the Instituto Bernabeu Implantation Failure Unit in Alicante explain, in the first instance, how the immune system which is responsible for “protecting us from any foreign organism that might attack us” works. Dr Belén Moliner, a gynaecologist at IB, also adds that there are different types of immunity. On the one hand, we have innate immunity which is present in all living things. On the other, we have acquired immunity which is only present in human beings and it is this immunity which enables antibody creation. This means that when the body comes into contact with an infection it has had before, it can respond “quickly and in a coordinated manner to the infection in order to defend itself.” This happens because it has a memory and is therefore able to remember and identify molecules, such as bacteria, which may be harmful.
If we apply this throughout the pregnancy, it’s necessary to take into account that the embryo is a set of cells that the mother’s immune system needs to identify adequately in order to allow for implantation. This is an indication, therefore, of the “important role the immune system plays in embryo implantation, along with many other factors.”
What defences do we have in our immune system that are key to this process? The Implantation Failure Unit at Instituto Bernabeu explains that “we are now able to detect certain molecules that we know are important to implantation and in making it happen.” More specifically, the most studied ones in the uterus are molecules called natural killers and T helper lymphocytes.
Natural killers are molecules that, following implantation, enable the embryo to develop small tentacles which are the beginnings of blood vessels and which will be used for feeding. However, despite their importance, further to extensive research, experts have determined that “patients with an excess quantity of these molecules have a greater number of recurrent pregnancy losses. An excess number of natural killers actually leads to an overly aggressive implantation in the endometrium” and this means that pregnancy is not actually achieved in the end.
The second type of defences which are important to implantation are T helper lymphocytes. These are molecules that help the immune system to determine if something is a bacteria and, if so, if it needs to be filled with antibodies in order to defend the body against it. There are two types of T helper, the LTH1 and the LTH1, and disparities in this type of defences can negatively affect embryo implantation.
Furthermore, the clinic in Alicante insists on the “importance of balance in the immune system; that all the cells are in the right place and in the right number. If balance is not achieved, perhaps it is down to a particular reason and that reason might be behind an inability to fall pregnant. On the whole, an altered immune system may be linked to recurrent pregnancy loss and implantation failure. And this is why the immune system is an important part of embryo implantation”.
Once the molecules present in the immune system and their influence on achieving pregnancy have been detected, how can we analyse them to determine if they are adequately balanced? Instituto Bernabeu has analysis systems for determining if there is an immunity issue in cases of embryo implantation failure or recurrent pregnancy loss. Natural killers and the two types of T helper were analysed. This analysis, which is part of an integrated programme within the Embryo Immunology Unit at Instituto Bernabeu, means that experts at the clinic in Alicante are sure that “everything is how it should be; that there are neither too many nor too few natural killer molecules; and can see if there is an imbalance in the T helpers so that an attempt at rectifying this can be carried out.”
With reference to the analysis, Dr Belén Lledó, molecular biologist at IB, explains that an analysis is carried out in order to evaluate the patient’s immune system activity. “There are lines of research which aim to detect any other molecule which might explain implantation failure or recurrent pregnancy loss.” With reference to the natural killers, “they are counted and the different types are observed so that more information on those reproduction issues can be gathered.”
Analyses of this type are now a reality in leading assisted reproduction clinics and help in ensuring that many patients can fulfil their dream of having a child. But research on the role played by the human immune system in terms of a successful pregnancy is still on-going and progressing. This field of research is important because the immune system itself is very important, and even more so in cases of embryo implantation.
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