FCGR2A and rheumatoid arthritis: Incomplete lysine clipping does likely not affect FcγR and FcRn binding but influences complement activation due to the reduction of the hexamerization potential of IgG.[62, 63] Notably, elevated carboxypeptidase B activity in RA and osteoarthritis is associated with a reduction of inflammatory‐mediated damage in the joints due to the cleavage of proinflammatory peptides of the complement system.[64, 65] In line with these observations, we detect a positive correlation trend of C‐terminal lysine abundance with inflammatory and disease markers (Figure 6).