TRIM21 and infection: A single point mutation in IgG, H433A, has been demonstrated to prevent TRIM21 interaction (Foss et al, 2016) and abolish its function: Antibodies with mutation H433A lose TRIM21 antiviral activity in vitro, in both cell lines (McEwan et al, 2012) and primary human macrophages (Labzin et al, 2019), and in vivo in a mouse model of infection (Bottermann et al, 2018).