The apoptotic-cell receptor CR3, but not ανβ5, is a regulator of human dendritic-cell immunostimulatory function

Dendritic cells (DCs) that capture apoptotic cells (ACs) in the steady state mediate peripheral tolerance to self-antigens. ACs are recognized by an array of receptors on DCs, the redundancy of which is not completely defined. We made use of an AC surrogate system to address the individual roles of the alpha v beta 5 and complement receptors (CRs) in the phagocytosis and induction of immunity. CR3 and CR4, while substantially less efficient than alpha v beta 5 in internalizing ACs, initiate signals that render DCs tolerogenic. Responding T cells show impaired proliferation and IFN gamma production and subsequently die by apoptosis. While tolerogenic DCs are not induced via alpha v beta 5, coligation of CR3 and alpha v beta 5 maintains the DC's tolerogenic profile. This immunomodulatory role, however, is countered by a significant inflammatory stimulus such as bacterial infection. Overall, our data suggest that under steady-state conditions, signaling via CRs predominates to render DCs tolerogenic.