LAMP1-targeting signals target antigen expression in the MHC class II–processing compartment. Intracellular localizations of V_H-HA1 and Sig-V_H-HA1-LAMP1 were assessed by immunofluorescence, using anti-HA1 and anti–I-A^k Abs. Images were captured with a Leica TCS SP2 microscope with a Pl Apo oil objective, 63×/1.4 numerical aperture (Leica, Milan, Italy). Cells were stained using HA1-FITC and I-A^K-TRIC mAbs. Images were processed with Leica confocal software.