Evidence for Multiple Sites of Interaction between IL‐12 and Its Receptor

Abstract

We have previously described the identification of a protein, now designated IL-12R beta 1, that binds 125I-huIL-12 with a Kd of about 10 nM, corresponding to the low affinity 125I-huIL-12 binding sites seen on PHA-activated human lymphoblasts. Using expression cloning techniques, we have recently identified an additional IL-12-binding protein subunit, IL-12R beta 2, which binds 125I-huIL-12 with a Kd of about 5 nM when expressed alone in COS-7 cells. Coexpression of IL-12R beta 1 and IL-12R beta 2 in COS-7 cells results in formation of two classes of 125 I-huIL-12-binding sites with Kds of about 50 pM and 5 nM. Mouse IL-12 p40 subunit homodimer (mo(p40)2) blocked 125I-huIL-12 binding to human IL-12R beta 1, but did not inhibit binding to human IL-12R beta 2. In contrast, anti-huIL-12 monoclonal antibody 20C2, which does not block 125I-huIL-12 binding to human IL-12R beta 1, completely blocked binding to human IL-12R beta 2. These results demonstrate that two classes of IL-12 inhibitors, one that primarily blocks IL-12/IL-12R beta 1 interaction (e.g., mo(p40)2), and one that primarily blocks IL-12/IL-12R beta 2 interaction (e.g., 20C2), can be identified.

A Novel Role of CD30L/CD30 Signaling by T-T Cell Interaction in Th1 Response against Mycobacterial Infection

“…ϩ T cell response to IL-12 is dependent on the expression of high-affinity IL-12R (39,40), composed of two IL-12R subunits, ␤1 and ␤2 (41,42). IFN-␥ activates Jak1 and Jak2, causing the phosphorylation, dimerization, and nuclear translocation of STAT1 which is important for the induction of T-bet (43).…”

Polymorphisms in the Il12b gene affect structure and expression of IL-12 in NOD and other autoimmune-prone mouse strains

“…Multiple sites of interaction between IL-12 and its receptor 7 have been demonstrated but the identity of the residue(s) of mouse IL-12p40 involved in this interaction are unknown. It is possible that the M → T substitution which results in a serologically defined change may also alter the binding affinity for IL-12p40 and its receptor.…”

“…5,6 The IL-12p40 homodimer binds to the ␤1 subunit of the IL-12 receptor but is unable to mediate the biological actions of IL-12p75. [7][8][9] It is therefore a potent antagonist of bioactive IL-12 and could play a role in immune regulation.…”

A novel class of anti-IL-12p40 antibodies

“…Monomeric IL-12p40 has been shown to compete directly with IL-12 for binding to IL-12Rβ1, 23 and neutralizing IL-12p40-specific antibodies that act via inhibition of IL-12/23 binding to IL-12Rβ1 have been characterized. In contrast, an antibody specific for heterodimeric IL-12, but not for its individual subunits, was able to inhibit the binding of IL-12 to IL-12Rβ2.…”

“…In contrast, an antibody specific for heterodimeric IL-12, but not for its individual subunits, was able to inhibit the binding of IL-12 to IL-12Rβ2. 23,24 It has been postulated that the binding of IL-12 to IL-12Rβ2 occurs at the IL-12p35 subunit or the heterodimeric interface. 25 Likewise, the binding of IL-23 to IL-23R is postulated to occur at the IL-23p19 subunit or the heterodimeric interface.…”