MLL gene rearrangements in infant leukemia vary with age at diagnosis and selected demographic factors: a Children's Oncology Group (COG) study.

Background: Infant leukemias have a high frequency of mixed lineage leukemia (MLL) gene rearrangements.

Procedure: Using data from a large etiologic study, we evaluated the distribution of selected demographic factors among 374 infant leukemia cases by leukemic subtype, MLL status and diagnosis age.

Results: Overall, 228 cases were MLL+.

Malignant transformation initiated by Mll-AF9: gene dosage and critical target cells.

The pathways by which oncogenes, such as MLL-AF9, initiate transformation and leukemia in humans and mice are incompletely defined. In a study of target cells and oncogene dosage, we found that Mll-AF9, when under endogenous regulatory control, efficiently transformed LSK (Lin(-)Sca1(+)c-kit(+)) stem cells, while committed granulocyte-monocyte progenitors (GMPs) were transformation resistant and did not cause leukemia. Mll-AF9 was expressed at higher levels in hematopoietic stem (HSC) than GMP cells.

Engrafted neural progenitor cells express a tissue-restricted reporter gene associated with differentiated retinal photoreceptor cells.

Neural progenitor cells (NPCs) have shown ability to repair injured CNS, and might provide precursors to retinal neurons. NPCs were isolated from the brains of 14 day murine embryos of transgenic mice that express beta-galactosidase (beta-gal) on the arrestin promoter, which specifically directs expression to retinal photoreceptor cells. NPCs were transferred to adult, syngeneic mice via inoculation into the anterior chamber of the eye, the peritoneal cavity, or the brain.

The antigen-presenting activity of fresh, adult parenchymal microglia and perivascular cells from retina.

Although several observations show local T cell recognition of retinal Ag, there has been no direct demonstration that the APC were retinal derived, rather than recruited. In this study, CD45(+) cells isolated from immunologically quiescent murine retina were tested in vitro for functional evidence of Ag presentation to naive and Ag-experienced CD4 T cells specific for beta-galactosidase. Because CD45(+) cells from brain have been reported to be efficient APC, they were included for comparison.

Cultivation at 37 degrees C enhances Borrelia burgdorferi sensu stricto infectivity for hamsters.

Borrelia burgdorferi sensu stricto (s.s.), the causative agent of Lyme disease in North America is transmitted to the mammalian host by ticks belonging to the genus, Ixodes.