CD23, is expressed on a variety of haematopoietic cell types and displ
ays pleiotropic activities in vitro. Here Jean-Yves Bonnefoy and colle
gues discuss a novel interaction between CD23 and the alpha chains of
the beta(2) integrins, CD11b and CD11c, that leads to a proinflammator
y pattern of macrophage activation. They describe how neutralizing ant
ibodies to CD23 can decrease the severity of murine arthritis.