Views of the Fc region of human immunoglobulin A (IgA) with interaction sites for key host receptors highlighted in the upper images, and those for bacterial IgA binding proteins in the lower ones. The remarkable co-localisation of these sites illustrates how various bacterial pathogens have co-opted sites on immunoglobulins as an effective means to block the elimination mechanisms which immunoglobulins normally trigger. See pp. 1651–1658 for further information. Image provided by J. Woof.