The ability of the B cell antigen receptors (BCRs) to enhance MHC class II-restricted antigen presentation was ascribed to mlg-associated Ig/Ig heterodimers. The relative role of Ig and Ig subunits in antigen presentation was investigated by fusing their cytoplasmic tails to the extracellular and transmembrane domains of Fc receptors. Ig and Ig chimera mediate antigen internalization and increase the efficiency of antigen presentation, but they drive antigens to different endosomal compartments. Furthermore, antigens internalized by either chimera are degraded and presented with different kinetics. The cytoplasmic tail of Ig targets antigen towards a major population of newly synthesized MHC class II located in class II-rich compartments. In contrast, Ig targets antigen towards a minor population of recycling MHC class II molecules, located in transferrin receptor-containing endosomes. Altogether, our data indicate that the composition of BCR could be therefore an important way to modulate the immune response.