Role of MCs in IgE- and dendritic-cell–mediated antigen-specific T-cell expansion. (A) In a conventional antigen-presentation model, dendritic cells (DCs) incorporate antigens (Ags) and present antigen to naive T (T_N) or memory T (T_H2) cells. (B) In the MC-mediated, IgE-mediated, and DC-mediated antigen presentation model, IgE/antigen-FcϵRI crosslinking promotes antigen internalization and apoptosis in MCs. DCs then uptake the apoptotic MCs (aMCs) carrying internalized antigens, and thus can efficiently present the antigen to antigen-specific memory T cells.