Cross-presentation of F37A was proteasome-dependent.

DC2.4 cells were pretreated for 1 h with MG132 (reversible proteasome inhibitor), epoxomicin (irreversible proteasome inhibitor), or chloroquine (lysosome inhibitor) and then co-cultured with RF33.70 cells for 20 h in the continued presence of the inhibitor. Cross-presentation was then determined by measuring the level of IL-2 produced from the RF33.70 cells (as detailed in Materials and Methods). Cross-presentation of F37A was reduced by the proteasome inhibitor, but was increased by chloroquine as compared to the control group (no inhibitor). Each bar indicates percent inhibition in the production of IL-2 concentration compared to that of the control (no inhibitor).*P<0.05, **P<0.01 vs. control.