IL-12 Receptor β2 (IL-12Rβ2)-Deficient Mice Are Defective in IL-12-Mediated Signaling Despite the Presence of High Affinity IL-12 Binding Sites

Abstract

Two subunits of the IL-12 receptor (IL-12R), IL-12Rβ1 and IL-12Rβ2, have been identified and cloned. Previous studies demonstrated that the IL-12Rβ1 subunit was required for mouse T and NK cells to respond to IL-12 in vivo. To investigate the role of IL-12Rβ2 in IL-12 signaling, we have generated IL-12Rβ2-deficient (IL-12Rβ2−/−) mice by targeted mutation in embryonic stem (ES) cells. Although Con A-activated splenocytes from IL-12Rβ2−/− mice still bind IL-12 with both high and low affinity, no IL-12-induced biological functions can be detected. Con A-activated splenocytes of IL-12Rβ2−/− mice failed to produce IFN-γ or proliferate in response to IL-12 stimulation. NK lytic activity of IL-12Rβ2−/− splenocytes was not induced when incubated with IL-12. IL-12Rβ2−/− splenocytes were deficient in IFN-γ secretion when stimulated with either Con A or anti-CD3 mAb in vitro. Furthermore, IL-12Rβ2−/− mice were deficient in vivo in their ability to produce IFN-γ following endotoxin administration and to generate a type 1 cytokine response. IL-12-mediated signal transduction was also defective as measured by phosphorylation of STAT4. These results demonstrate that although mouse IL-12Rβ1 is the subunit primarily responsible for binding IL-12, IL-12Rβ2 plays an essential role in mediating the biological functions of IL-12 in mice.

TNF Enhances CD4+ T Cell Alloproliferation, IFN-γ Responses, and Intestinal Graft-Versus-Host Disease by IL-12-Independent Mechanisms

“…Con A-activated splenocytes from both control B6 and B6.IL-12R Ϫ/Ϫ mice proliferate equally well when stimulated with IL-2. However, a marked reduction in the production of IFN-␥ by the B6.IL-12R Ϫ/Ϫ spleen cells occurs (37). As illustrated by the results of the present studies, alloantigen-induced proliferative responses of B6.IL-12R Ϫ/Ϫ spleen cells are similar to those of B6 spleen cells, but IFN-␥ responses are reduced, as previously reported, in studies assessing both alloantigen-and Ag-induced T cell responses.…”

“…This conclusion is based on results of experiments using responder T cells that lack the IL-12R ␤2 subunit of the IL-12R (37). In cells from the B6.IL-12R Ϫ/Ϫ mouse strain used in these studies, the IL-12 ␤1 subunit of the IL-12R still binds the IL-12 with both high and low affinity receptors, but no IL-12 biological function can be detected (35).…”

“…IL-18, an IL-1-related factor (38 -40), also has been shown to be a selective activator of IFN-␥ in Th1, but not Th2, cells. Both IL-1 and IL-18 activate a IRAK (a kinase associated with IL-1R) (36) and NF-B in Th1 cells (37)(38) and TNFR-associated factor 6 (38). IRAK-deficient mice have defective IL-18-mediated Th1-type responses in vivo (41).…”

Reduced expression of IL-12 receptor β2 and IL-18 receptor α genes in natural killer cells and macrophages derived from B6-mi/mi mice

“…18,[22][23][24][25][26][27] Therefore, we analyzed the IFN-g production in NK cells and macrophages from B6-þ / þ and B6-mi/mi mice. An enzyme-linked immunosorbent assay (ELISA) was used to measure the IFN-g production levels of freshly isolated or cultured NK 1.1 þ cells, peritoneal macrophages and cultured Mac-1 þ cells.…”

“…22 Both NK cells and macrophages express the receptors for both IL-12 and IL-18, and produce IFN-g in response to stimulation with IL-12, IL-18, and IL-12 plus IL-18. 18,[22][23][24][25][26][27] The abnormal phenotypes of B6-mi/mi NK cells resemble those of mice that are deficient in IL-12 or IL-18 signaling. [8][9][10]18,[22][23][24][25][26][27] The administration of IL-12 or IL-18 did not recover the decreased NK activity of B6-mi/mi mice (our unpublished data).…”