CD274 and cancer: Further, like in suppression of the host effector T cell response in cancers we postulate that exosomes with negative actions on the effector immune system in some of the potential COVID‐19 therapeutic plasmas may express check point inhibitory surface PD‐L1 (Chen et al., 2018; Poggio et al., 2019), or other co‐inhibitory receptors, as found in parasite infections (Dookie et al., 2020).