March 2012 | Volume 209, No. 3
Brief Definitive Reports
- Lethal myelofibrosis induced by Bmi1-deficient hematopoietic cells unveils a tumor suppressor function of the polycomb group genes
Polycomb group gene Bmi1 functions as a tumor suppressor in myelofibrosis.
- Agammaglobulinemia and absent B lineage cells in a patient lacking the p85α subunit of PI3K
A patient with a homozygous premature stop codon in PIK3R1 showed an early developmental block in B cell development but minimal effects in other organ systems.
- Primary Epstein-Barr virus infection does not erode preexisting CD8+ T cell memory in humans
Bystander activation of human CD8+ T cells specific for influenza or cytomegalovirus during primary Epstein-Barr virus infection does not result in preexisting memory T cell attrition.
- Stimulation of the neurotrophin receptor TrkB on astrocytes drives nitric oxide production and neurodegeneration
The neurotrophin receptor TrkB is up-regulated on astrocytes in white matter lesions from multiple sclerosis patients, and mice lacking TrkB specifically in astrocytes are more resistant to experimental autoimmune encephalomyelitis–induced neurodegeneration.
- Osteoclasts promote the formation of hematopoietic stem cell niches in the bone marrow
Osteoclasts promote the formation of the HSC niche by inducing the differentiation of osteoblastic cells from mesenchymal stem cells.
- HMGB1 promotes recruitment of inflammatory cells to damaged tissues by forming a complex with CXCL12 and signaling via CXCR4
CXCL12 forms a complex with HMGB1 that binds to the chemokine receptor CXCR4 and increases inflammatory cell migration.
- Neutrophil depletion impairs natural killer cell maturation, function, and homeostasis
Neutropenia in mice and humans results in the generation of NK cells with an immature and hyporesponsive phenotype.
- Dual regulation of IRF4 function in T and B cells is required for the coordination of T–B cell interactions and the prevention of autoimmunity
Female mice lacking DEF6 and SWAP70 develop a lupus-like syndrome through dysregulation of IRF4 in activated B cells and plasma cells.
- A germinal center–independent pathway generates unswitched memory B cells early in the primary response
Early IgM+ and switched Ig+ memory B cells develop from a germinal center (GC)–independent pathway, whereas late switched memory cells are GC dependent.
- Trefoil factor 2 rapidly induces interleukin 33 to promote type 2 immunity during allergic asthma and hookworm infection
The repair protein trefoil factor 2 promotes Th2 responses to helminth infection and allergens in part by inducing IL-33.
- Thymic negative selection is functional in NOD mice
Erk1/2-dependent TCR decisions, but not negative selection, are impaired in NOD thymocytes, leading to preferential development of αβ CD4+CD8+ thymocytes over γδ thymocytes and saturation of selection niches in TCR tg mouse models.