Interleukin12 receptor subunit beta 1 (IL12RB1) is a type I transmembrane protein that belongs to the hemopoietin receptor superfamily. IL12RB1 can spontaneously form homodimers and -oligomers, which are able to bind IL12 with only low affinity. IL12 high affinity receptor complex is composed of two subunits designated IL12RB1 and IL12RB2. While IL12RB1 interacts with the IL-12p40 subunit, IL-12p35 is mainly connecting with IL12RB2. This receptor chain is also responsible for transmitting the IL12 signal into the cell. IL12RB1, to the contrary, is also part of the IL23R, where it interacts with the p40 subunit of IL23. IL12RB1 is expressed in activated T cells, NK cells and B cells.