Proteases influence recognition of lipopeptides. (A and B) lipo-12 and DDM were treated with proteinase K or pronase, or were mock treated in the same buffer without the proteases, and were used to stimulate 1A3 T cells and CD1a-restricted J.RT3/CD8-2 cells, respectively. Error bars represent SEM. (C) To test whether protease-treated lipo-12 itself or the inactivated proteases present in the digestion mixture were toxic to 1A3 T cells, high concentrations (10 µg/ml) of these mixtures were tested in the presence of a suboptimal amount of untreated lipo-12. (D) lipo-12 was added to DCs in the continuous absence or presence of 10 ng/ml of the protease inhibitor LHVS, and proliferation of 1A3 T cells was measured. This experiment was performed twice with essentially the same result.