Negative regulation of lymphocyte activation and autoimmunity by the molecular adaptor Cbl-b.
Bachmaier K,
Krawczyk C,
Kozieradzki I,
Kong YY,
Sasaki T,
Oliveira-dos-Santos A,
Mariathasan S,
Bouchard D,
Wakeham A,
Itie A,
Le J,
Ohashi PS,
Sarosi I,
Nishina H,
Lipkowitz S,
Penninger JM.
Amgen Institute, Department of Medical Biophysics, University of Toronto, Ontario, Canada.
The signalling thresholds of antigen receptors and co-stimulatory receptors determine immunity or tolerance to self molecules. Changes in co-stimulatory pathways can lead to enhanced activation of lymphocytes and autoimmunity, or the induction of clonal anergy. The molecular mechanisms that maintain immunotolerance in vivo and integrate co-stimulatory signals with antigen receptor signals in T and B lymphocytes are poorly understood. Members of the Cbl/Sli family of molecular adaptors function downstream from growth factor and antigen receptors. Here we show that gene-targeted mice lacking the adaptor Cbl-b develop spontaneous autoimmunity characterized by auto-antibody production, infiltration of activated T and B lymphocytes into multiple organs, and parenchymal damage. Resting cbl-b(-/-) lymphocytes hyperproliferate upon antigen receptor stimulation, and cbl-b(-/-) T cells display specific hyperproduction of the T-cell growth factor interleukin-2, but not interferon-gamma or tumour necrosis factor-alpha. Mutation of Cbl-b uncouples T-cell proliferation, interleukin-2 production and phosphorylation of the GDP/GTP exchange factor Vav1 from the requirement for CD28 co-stimulation. Cbl-b is thus a key regulator of activation thresholds in mature lymphocytes and immunological tolerance and autoimmunity.
PMID: 10646608 [PubMed - indexed for MEDLINE]