Immunoproteasomes are a special class of proteasomes, which can be induced with IFN-γ in an inflammatory environment. In recent years, it became evident that certain immune cell types constitutively express high levels of immunoproteasomes. However, information regarding the basal expression of proteolytically active immunoproteasome subunits in different types of immune cells is still rare. Hence, we quantified standard proteasome subunits (β1c, β2c, β5c) and immunoproteasome subunits (LMP2, MECL-1, LMP7) in the major murine (CD4⁺ T cells, CD8⁺ T cells, CD19⁺ B cells, CD11c⁺ dendritic cells, CD49d⁺ natural killer cells, Ly-6G⁺ neutrophils) and human immune cell (CD4⁺ T cells, CD8⁺ T cells, CD19⁺ B cells, CD1c⁺CD141⁺ myeloid dendritic cells, CD56⁺ natural killer cells, granulocytes) subsets. The different human immune cell types were isolated from peripheral blood and the murine immune cell subsets from spleen. We found that proteasomes of most immune cell subsets mainly consist of immunoproteasome subunits. Our data will serve as a reference and guideline for immunoproteasome expression and imply a special role of immunoproteasomes in immune cells.