- The selective proteasome inhibitors lactacystin and epoxomicin can be used to either up- or down-regulate antigen presentation at nontoxic doses. Schwarz, K., de Giuli, R., Schmidtke, G., Kostka, S., van den Broek, M., Kim, K.B., Crews, C.M., Kraft, R., Groettrup, M. J. Immunol. (2000)