IL-12 p40 homodimer, but not IL-12 p70, induces the expression of IL-16 in microglia and macrophages

Abstract

IL-16, a leukocyte chemoattractant factor (LCF), is involved in the disease process of multiple sclerosis and other autoimmune disorders. However, mechanisms by which this LCF is expressed are poorly understood. The present study underlines the importance of IL-12 p40 homodimer (p40 2 ), the so-called biologically inactive molecule, in inducing the expression of IL-16 in primary mouse and human microglia, mouse BV-2 microglial cells, mouse peritoneal macrophages, and RAW264.7 cells. In contrast, IL-12 p70, the bioactive heterodimeric cytokine, was unable to induce the expression of IL-16 in any of these cell types. Similarly IL-12 p40 2 also induced the activation of IL-16 promoter in microglia. Among various stimuli tested, p40 2 was the most potent one followed by p40 monomer, IL-16 and IL-23 in inducing the activation of IL-16 promoter in microglial cells. Furthermore, induction of IL-16 mRNA expression by over-expression of p40, but not p35, cDNA and induction of IL-16 expression by p40 2 in microglia isolated from IL-12p35 (−/−) mice confirm that p40, but not p35, is responsible for the induction of IL-16. Finally, by using primary microglia isolated from IL-12Rβ1 (−/−) and IL-12Rβ2 (−/−) mice, we demonstrate that p40 2 induces the expression of this LCF via IL-12Rβ1 but not IL-12Rβ2. These results delineate a novel biological function of p40 2 and raise the possibility that biological function of IL-12 p40 2 maybe different from IL-12 p70.

Antitumor effects of a tumor cell vaccine expressing a membrane-bound form of the IL-12 p35 subunit

“…than the secreted form. [21][22][23][24][25][26][27][28][29][30][31][32][33][34] Hence in this study we investigated whether the p35 subunit of IL-12 has IL-12-like biological activity by examining the immunity induced by a clone of MethA fibrosarcoma cells expressing p35 in membrane-bound form so that it could be expressed without co-expression of p40 subunit. We found that tumor cells expressing mbIL-12p35 had reduced tumorigenicity, and induced antitumor immunity to MethA cells in a CD8 + T cell-dependent manner.…”

Interleukin‐12 (IL‐12), but not IL‐23, induces the expression of IL‐7 in microglia and macrophages: implications for multiple sclerosis

“…To investigate the validity of this possibility, we examined the effect of transient expression of mouse p40, p19 and p35 cDNA on the expression of IL-7 in BV-2 microglial cells. 27 As shown by semi-quantitative RT-PCR analysis (Fig. 4a) and quantitative real-time PCR analysis (Fig.…”

“…25,26 We have recently demonstrated that p40 2 , but not IL-12p70, induces the expression of IL-16 and lymphotoxin a in various immune cells. 27,28 Here we describe that IL-12, but not IL-23 and other p40 family members, induces the expression of IL-7 in microglia, macrophages and astrocytes. Furthermore, we demonstrate that IL-12 induces the expression of IL-7 via both IL-12Rb1 and IL-12Rb2.…”

“…25,27 Cells were washed three times with the same media at 4°and were maintained at 37°in a humidified incubator containing 5% CO 2 in air. Cells were plated in culture dishes in RPMI-1640 medium containing 1% FBS, L-glutamine and antibiotic-antimycotic mixture.…”

“…27,28,31 Briefly, coverslips containing 200-300 cells/mm 2 were fixed with 4% paraformaldehyde for 15 min, followed by treatment with cold ethanol (À20°) for 5 min and two rinses in PBS. Samples were blocked with 3% BSA in PBS containing Tween 20 (PBST) for 30 min and incubated in PBST containing 1% BSA and rabbit anti-IL-7 (1 : 50).…”