Differential regulation of the interleukin-12 receptor during the innate immune response to Leishmania major

Previous studies have shown the central role of interleukin 12 (IL-12) in the development of resistance to Leishmania major infection in C3H mice. We now show that during the innate immune response the lymph node cells of L. major-infected C3H mice upregulate the IL-12 receptor on CD4(+), CD8(+), and B220(+) cells. An increase in the ability of the lymph node cells to bind IL-12 correlates with 9.3- and 4.6-fold increases in the mRNA expression levels of the IL-12Rbeta1 and -beta2 subunits, respectively. In contrast, BALB/c mice, which are susceptible to L. major infection, have no increase in the ability of the lymph node cells to bind IL-12 and correspondingly smaller increases in the mRNA expression levels of the IL-12Rbeta1 and -beta2 subunits of 2- and 1.5-fold, respectively. Neutralizing IL-4 and the administration of exogenous IL-12 upregulate IL-12R expression in BALB/c mice, while the neutralization of IL-12 in C3H mice blocks increased IL-12 receptor expression. These experiments reveal an important role for the regulation of the IL-12 receptor during the innate immune response after infection of mice with a pathogen.