By Anna Tarasova ’19

The immune system of a fetus differs significantly from that of an infant or adult. During the second trimester of pregnancy, a fetus’s immune system is able to recognize antigens, or foreign cells, and conduct an immune response using dendritic cells. Dendritic cells are antigen-presenting cells (APC), which means that they place antigens along with specific receptors on their cell surface to activate and signal to other immune cells called T cells.

Dr. Naomi McGovern of the Singapore Immunology Network and her colleagues analyzed and compared fetal and adult APC using flow cytometry and gene array analysis. Flow cytometry allows for the evaluation of cell components using fluorescence and laser technology, while gene array analysis is used to differentiate the expression of genes in two samples. The researchers found that some fetal dendritic cells are able to interact with T cells when the fetus is 10 weeks old and are able to migrate through the lymphatic system when the fetus is 16 weeks old. It was previously thought that the fetal immune system is underdeveloped and thus the fetus has a suppressed immune response. However, this study shows that this system is able to produce an appropriate immune response to the myriad of external stimuli that the fetus is exposed to in utero. Furthermore, Dr. McGovern cultured fetal and adult dendritic cells together and found that this combination promoted immune suppression in the fetal cells by decreasing T cell proliferation and the release of inflammatory molecules. The maternal and fetal immune systems are foreign to each other, but cells of one system do not attack the other, suggesting that there may be a mechanism for the two systems’ cooperation. This lead the researchers to believe that rather than being underdeveloped, the fetus’s immune system intentionally lacks a strong response to maternal tissue.

References:

1. N. McGovern et al., Human fetal dendritic cells promote prenatal t-cell immune suppression through arginase-2. Nature, 2017. doi:10.1038/nature22795
2. https://upload.wikimedia.org/wikipedia/commons/b/b0/Embryo_week_9-10.jpg