Selective Expression of an Interleukin-12 Receptor Component by Human T Helper 1 Cells

Abstract

Interleukin-12 (IL-12), a heterodimeric cytokine produced by activated monocytes and dendritic cells, plays a crucial role in regulating interferon (IFN)-γ production and in the generation of IFN–γ–producing T helper 1 (Th1) cells. Here we show that the IL-12 receptor (IL12R) β2 subunit, a recently cloned binding and signal transducing component of the IL-12R, is expressed on human Th1 but not Th2 clones and is induced during differentiation of human naive cells along the Th1 but not the Th2 pathway. IL-12 and type I but not type II interferons induce expression of the IL-12R β2 chain during in vitro T cell differentiation after antigen receptor triggering. The selective expression and regulation of the IL-12R β2 subunit may help to understand the basis of Th1/Th2 differentiation and may provide therapeutic options for altering the Th1/Th2 balance in several immuno-pathological conditions such as autoimmune diseases and allergies.

Interleukin-12 Induces Expression of Interferon Regulatory Factor-1 via Signal Transducer and Activator of Transcription-4 in Human T Helper Type 1 Cells

“…3. Consistent with our previous findings (21) and those of other laboratories (19,20,53), IL-12 activated a STAT complex only in Th1 cells but not in Th2 cells. IFN-␣ strongly induced two STAT complexes with different electrophoretic mobility both in Th1 and Th2 cells, whereas only Th2 cells were sensitive to IFN-␥.…”

“…These findings are consistent with the previously described observation that IFN-␣ activates STAT-4 in human mitogen-activated lymphoblasts and in human Th1 and Th2 cells (50,56). The complex induced in IL-12-treated Th1 cells is abrogated with STAT-4 specific antibodies, confirming previously published results (17,20,21). Addition of anti-STAT-3 antibodies did not significantly change the DNAbinding complexes, suggesting that STAT-3 does not play a major role in activating the IRF-1 promoter in response to the cytokines tested in this study.…”

“…To generate the 32 P-labeled 280-base pair-long antisense IRF-1 RNA probe, the plasmid pBS IRF-1 was linearized with EcoRI and transcribed by T7 polymerase. A 327-base pair DNA fragment encompassing the cytoplasmic region of the human IL-12R␤2 subunit was subcloned in pGEM 3Z (21). This construct was linearized with EcoRI, and radiolabeled antisense transcripts were synthesized with SP6 polymerase and a commercial kit according to the manufacturer's protocol (Promega, Madison, WI).…”

“…To study whether the transcription factor IRF-1 may also play a role in human T helper cell development, we have analyzed expression of IRF-1 transcripts in human Th1 and Th2 cells generated from cord blood (21,50). The T helper phenotype has been determined by the analysis of intracellular IFN-␥ and IL-4 production after restimulation of T cells with phorbol 12-myristate 13-acetate and ionomycin (Fig.…”

“…Signaling of these two cytokines is mediated through the activation of specific signal transducer and activator of transcription (STAT) proteins. STAT-6 is activated by IL-4 in Th2 cells (14 -16), and IL-12 activates STAT-4 in Th1 cells (17)(18)(19)(20)(21). Studies on knockout mice for these transcription factors clearly indicate the pivotal role of STAT-6 and STAT-4 in T helper cell differentiation.…”