ABSTRACT
It has been proposed that the maintenance of T cell anergy depends on the induction of negative regulatory factors. Differential display of reverse transcribed RNA was used to identify novel genes that might mediate this function in anergic Th1 clones. We report that anergic Th1 clones do indeed express a genetic program different from that of responsive T cells. Moreover, one gene, the general receptor of phosphoinositides 1 (GRP1), was selectively induced in anergic T cells. The GRP1, located in the plasma membrane, regulated integrin-mediated adhesion and was invariably associated with unresponsiveness in multiple models of anergy. T cells expressing retrovirally transduced GRP1 exhibited normal proliferation and cytokine production. However, GRP1-transduced T cells were not stable and rapidly lost GRP1 expression. Thus, although GRP1 may not directly mediate T cell anergy, it regulates cell expansion and survival, perhaps through its integrin-associated activities.
Subject(s)
Cell Adhesion Molecules/biosynthesis , Clonal Anergy , Integrins/physiology , Receptors, Cytoplasmic and Nuclear/biosynthesis , T-Lymphocyte Subsets/immunology , T-Lymphocyte Subsets/metabolism , Amino Acid Sequence , Animals , Antibodies/pharmacology , CD3 Complex/immunology , Cell Adhesion/immunology , Cell Membrane/immunology , Cell Membrane/metabolism , Chromosome Mapping , Clonal Anergy/genetics , Clone Cells , Gene Expression Regulation/immunology , Guanine Nucleotide Exchange Factors , Intercellular Adhesion Molecule-1/physiology , Lymphocyte Function-Associated Antigen-1/physiology , Mice , Mice, Inbred A , Mice, Inbred DBA , Mice, Transgenic , Molecular Sequence Data , Phosphatidylinositols/metabolism , Receptors, Antigen, T-Cell/antagonists & inhibitors , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/isolation & purification , Th1 Cells/immunology , Th1 Cells/metabolism , TransfectionABSTRACT
A novel T cell-specific adaptor protein, RIBP, was identified based on its ability to bind Rlk/Txk in a yeast two-hybrid screen of a mouse T cell lymphoma library. RIBP was also found to interact with a related member of the Tec family of tyrosine kinases, Itk. Expression of RIBP is restricted to T and natural killer cells and is upregulated substantially after T cell activation. RIBP-disrupted knockout mice displayed apparently normal T cell development. However, proliferation of RIBP-deficient T cells in response to T cell receptor (TCR)-mediated activation was significantly impaired. Furthermore, these activated T cells were defective in the production of interleukin (IL)-2 and interferon gamma, but not IL-4. These data suggest that RIBP plays an important role in TCR-mediated signal transduction pathways and that its binding to Itk and Rlk/Txk may regulate T cell differentiation.
Subject(s)
Adaptor Proteins, Signal Transducing , Carrier Proteins/genetics , Carrier Proteins/metabolism , Chromosome Mapping , Killer Cells, Natural/immunology , Lymphocyte Activation , Protein-Tyrosine Kinases/metabolism , T-Lymphocytes/immunology , Amino Acid Sequence , Animals , Cell Line , Cells, Cultured , Cloning, Molecular , Crosses, Genetic , Gene Library , Humans , Interleukin-2/biosynthesis , Lymphoma, T-Cell , Mice , Mice, Inbred Strains , Mice, Knockout , Molecular Sequence Data , Muridae , Recombinant Proteins/metabolism , Sequence Alignment , Sequence Homology, Amino Acid , Transfection , Tumor Cells, CulturedABSTRACT
Serum LH, FSH and LHRH concentrations and the LHRH content in the medial basal hypothalamus (MBH) and the preoptic area (POA) were measured by radioimmunoassay in male rats 33 days after anterior hypothalamic deafferentation (AHD) and/or castration. In castrate rats following AHD, there was a significant decrease in serum LH, FSH, and LHRH concentrations, whereas, in intact rats, serum LH was elevated in AHD over the sham AHD rats. Castration and AHD each caused a significant fall in the LHRH levels in the MBH; the decline was more pronounced in rats undergoing both castration and AHD. In contrast, deafferentation in intact and castrate rats resulted in the accumulation of LHRH activity in the POA. These studies support the suggestion that a) a substantial amount of LHRH normally found in the MBH of intact and castrate male rats originates in the rostral regions and, b) the LHRH-containing neural elements within the MBH have the competence to respond to a loss in the circulating testicular steroids.
