Receptor for interleukin-12. This subunit is the signaling component coupling to the JAK2/STAT4 pathway. Promotes the proliferation of T-cells as well as NK cells. Induces the promotion of T-cells towards the Th1 phenotype by strongly enhancing IFN-gamma production. Can also activate STAT3. Heterodimer/heterooligomer; disulfide-linked. The functional high affinity IL12 receptor is composed of I12RB1 and IL12RB2. Il12RB2 binds JAK2 (via its N-terminal) through a membrane-proximal region of the cytoplasmic domain (By similarity). Expressed in developing T-helper (TH) cells. Expressed at high levels in Th1 cells on day 3, 5 and 7 after primary activation. Very low expression in Th2 cells on day 3 and not detectable on day 5 nor day 7 after activation. Following T-cell activation, expression inhibited by IL4 and induced by IFN gamma. The WSXWS motif appears to be necessary for proper protein folding and thereby efficient intracellular transport and cell-surface receptor binding. The box 1 motif is required for JAK interaction and/or activation. On IL12 stimulation, phosphorylated on C-terminal tyrosine residues. Phosphorylation of any one of Tyr-757, Tyr-804 or Tyr-811 can activate STAT4, IFN-gamma production, and T-cell proliferation. Tyr-811 is the dominant site of cell proliferation. Lps-defective mice C57BL/10ScCr (Cr) mice carry a mutation in the IL12RB2 gene leading to the production of a truncated IL12 receptor beta 2 chain resulting in malfunction of the IL12-mediated IFN-gamma response. Belongs to the type I cytokine receptor family. Type 2 subfamily.