A glance at Wikipedia confirms that some pathogens are aware of PD-L1 and like to mess with proteins that regulate the immune system. Epstein-Barr Virus (EBV),

A glance at Wikipedia confirms that some pathogens are aware of PD-L1 and like to mess with proteins that regulate the immune system. Epstein-Barr Virus (EBV), the most common human virus, the herpes that 90% of people have had and a common cause of cancer, apparently has a protein that induces expression of PD-L1. Some other viruses in mice have been observed to do it. What a mess. I love immunology.