Fig. 1.

Space-filling diagrams showing the Fc fragments (yellow) of human IgA (A), IgE (B) and IgG (C) in complex with their leukocyte Fc receptors (blue), FcαRI, FcɛRI and FcγRIII, respectively, and two orthogonal views (D and E) of chicken IgY-Fc (domains Cυ3 and Cυ4). Residues 346–348 were modelled onto the crystal structure of chicken Fcυ3–4 for display purposes, although these residues were found to be disordered [5]. Cυ2 domains are not shown, although they were included in the IgY-Fc used in this study. Residues whose mutation had no effect are coloured green and labelled in (D); residues whose mutation inhibited binding to soluble CHIR-AB1 and/or MQ-NCSU monocytes are coloured red and labelled in (E).