# Proteasomes The **proteasome** is like a **blender** that breaks down damaged or unwanted proteins (such as pathogens/antigens) into pieces small enough for the cell to reuse. ### Proteasome Variations **Thymoproteasome:** aaa **Immunoproteasome:** aaa - Found within antigen-presenting cells (APCs) such as [[dendritic cells]] Both the thymoproteasome and the immunoproteasome generate nonamer peptides that are bound by MHC class I molecules. --- The immunoproteasome allows APCs activated by IFN-γ to generate different peptides than those generated by the standard proteasome found in all cells. This supports a broader immune response to pathogens by expanding the number of different peptides presented to T cells. In the thymus during positive selection, self peptides are presented to ensure that the thymocytes are capable of recognizing the host’s MHC molecules. The thymoproteasome allows these self peptides to have a lower affinity to the tested T-cell receptors. Each of these proteasomes serves a specific function in shaping the immune response.