Background：CD122 is a 70-75 kD IL-2 receptor b chain also known as IL-2Rb, which is also shared by the IL-15 receptor. It is constitutively expressed by NK cells and at lower levels by T cells, B cells, monocytes, and macrophages. The IL-2Rb chain can combine with either the common gamma subunit （gammac, CD132） alone or with the gammac subunit and the IL-2Ra subunit （CD25） to generate intermediate or high affinity IL-2 receptor complexes, respectively. CD122 expression levels can be upregulated by activation. The 5H4 antibody does not block IL-2 binding to the IL-2 receptor. CD122 is expressed on murine, but not human, CD8+ Tregs involved in the maintenance of T cell homeostasis.
