Coevolution of Mucosal Immunoglobulins and the Polymeric Immunoglobulin Receptor: Evidence That the Commensal Microbiota Provided the Driving Force

Figure 7

Theoretical model for changes in the structure of secretory Igs during evolution. (a) The structure for mammalian SIgA is adapted from the model of Woof and Russell [16] for human SIgA1, with permission from Nature Publishing Group. (b) and (c): Theoretical models for the structure of IgX/A from amphibians and birds and SIgT from teleost fish, respectively, are predicted from alignment of Ig heavy chain and pIgR sequences with mammalian homologs.