CD40LG and rheumatoid arthritis: We included peptides that we previously demonstrated were bound by IgG in rheumatoid arthritis (9, 21) as well as new peptides: homocitrulline-containing versions of IgG1-131 (which is bound by IgM in its native form post-COVID-19 and by IgG in its citrulline-containing form in rheumatoid arthritis (9)) and IgG1-236 (which includes a previously described peptide starting at position 238 of IgG1 that is highly bound by IgM post-COVID-19 (9)).