It would be interesting to study a) the biological effect of IgG containing no, one or two sialic acid residues at the Fc part and IgG with or without a Fab-sialylated part using different murine models (e.g. rheumatoid arthritis and thrombocytopenia and b) the SIGN-R1/DC-SIGN binding of sialylated IgG with and without removal of the Fab- and Fc-linked glycans. Here, CD209 is linked to rheumatoid arthritis.