CD4 and infection: Patient 2 received CD19-directed CAR-T cell therapy prior to their infection, had a CD4/CD8 ratio < 1 (associated with altered immune function), and had no detectable antibodies against SARS-CoV-2 until the regular approximately weekly administration of convalescent plasma therapy starting from day 103 onward (plasma was also administered once at day 78) [9,28].