Structural and Functional Analysis of Human Interleukin-12 Receptor

We established a panel of monoclonal antibodies(MAb)to human Interleukin-12receptor beta1 chain(IL-12R)by Signal Trap method。In this case，the cDNA for Tac signal sequence was replaced with IL-12R signal extracellular domain sequence.The chimeric cDAN was expressed and anti-Tac antibody was used to detect the chimeric protein.The transfected cells were used for immunization。Hybridomas were derived by conventional cell fusion and confirmed by positive staining with transfectants and negative with wild-type cells.We could obtain both neutralizing and non-neutralizing antibodies as determined by inhibition of IL-12 induced T cell proliferation assay and of radiolabelled ligand binding study.Immunoprecipitation disclosed putative p110 both from transfectants and PHA-stimulated human lymphocytes.We could draw the following conclusions on IL-12and IL-12R with newly developed mAb.·T CELL responsiveness TO IL-12required presence of monocytes and other antigen presenting cells.To be more specific，interaction between CD2onT cells and CD58on monocytes was essential in the T cell activation by IL-12·T cell responsiveness to IL-12was inhibited by IL-4 and enhanced by gammaIFN.Expression level of IL-12R on T cells was，however，not affected by either of cytokines.·We could co-immunoprecipitate 85 kDa protein along with IL-12R from T cells with our mAb.This newly identified protein was tyrosine-phosphorylated upon IL-12 stimulation.This was different from other known STAT and JAK proteins.This molecule could be an interesting clue to analyze IL-12/IL-12R signal transduction system。

We established a panel of monoclonal antibodies(mAb)to human Interleukin-12 receptor beta1chain(IL-12R)by Signal Trap method. In this case, the cDNA for Tac signal sequence was replaced with IL-12R signal+extracellular domain sequence. The chimeric cDAN was expressed and anti-Tac antibody was used to detect the chimeric protein. The transfected cells were used for immunization. Hybridomas were derived by conventional cell fusion and confirmed by positive staining with transfectants and negative with wild-type cells. We could obtain both neutralizing and non-neutralizing antibodies as determined by inhibition of IL-12 induced T cell proliferation assay and of radiolabelled ligand binding study. Immunoprecipitation disclosed putative p110 both from transfectants and PHA-stimulated human lymphocytes.We could draw the following conclusions on IL-12 and IL-12R with newly developed mAb.・T CELL responsiveness TO IL-12 required presence of monocytes and other antigen presenting cells. To be more specific, interaction between CD2 onT cells and CD58 on monocytes was essential in the T cell activation by IL-12・T cell responsiveness to IL-12 was inhibited by IL-4 and enhanced by gammaIFN.Expression level of IL-12R on T cells was, however, not affected by either of cytokines.・We could co-immunoprecipitate 85 kDa protein along with IL-12R from T cells with our mAb. This newly identified protein was tyrosine-phosphorylated upon IL-12 stimulation. This was different from other known STAT and JAK proteins. This molecule could be an interesting clue to analyze IL-12/IL-12R signal transduction system.