C5AR1 and COVID-19: Specifically, nivolumab was used to alleviate (cytotoxic T) T cell exhaustion that arose during SARS-CoV-2 infections [13], whereas avdoralimab and tocilizumab were expected to blockC5a/C5aR and IL6-IL6R pathways, which could bring about protective adaptive immunity [14] and block exuberant inflammation in COVID-19 pathogenesis [15].