CD8 T cells and dendritic cells: key players in the attenuated maternal immune response to influenza infection

• Plasmacytoid dendritic cells (pDCs) and CD8 T cells are critical for pregnancy.
• pDCs show increased CD86 and HLA-DR expression following infection in pregnancy.
• pDCs show increased PD-L1 expression following infection in pregnancy.
• CD8 T cells show increased PD-1 expression following infection in pregnancy.
• Blocking PD-L1 activity significantly improves maternal antiviral immunity.

Pregnancy provides a unique challenge for maternal immunity, requiring the ability to tolerate the presence of a semi-allogeneic foetus, and yet still being capable of inducing an immune response against invading pathogens. To achieve this, numerous changes must occur in the activity and function of maternal immune cells throughout the course of pregnancy. Respiratory viruses take advantage of these changes, altering the sensitive balance of maternal immunity, leaving the mother with increased susceptibility to viral infections and increased disease severity. Influenza virus is one of the most common respiratory virus infections during pregnancy, leading to an increased risk of ICU hospitalisations, pneumonia, acute respiratory distress syndrome and even death. Whilst much research has been performed to understand the changes that must take place in maternal immunity during pregnancy, considerable work is still needed to fully comprehend this tremendous feat. To date, few studies have focused on the alterations that occur in maternal immunity during respiratory virus infections. This review highlights the role of dendritic cells (DCs) and CD8 T cells during pregnancy, and the changes that occur in these antiviral cells following influenza virus infections.