IL-21 is expressed in Hodgkin lymphoma and activates STAT5: evidence that activated STAT5 is required for Hodgkin lymphomagenesis.

Classical Hodgkin lymphoma (HL) is a malignant disorder characterized by the presence of neoplastic mononucleated Hodgkin and multinucleated Reed-Sternberg cells. Here, we show that both the interleukin (IL)-21 receptor as well as IL-21 are expressed by HL cells. IL-21 activates signal transducer of activation and transcription 3 (STAT3) and STAT5 in HL cell lines and activated human B cells.

STAT5 regulates the self-renewal capacity and differentiation of human memory B cells and controls Bcl-6 expression.

It is unknown how B cells that mature during a germinal center reaction 'decide' between plasma or memory cell fate. Here we describe a previously unknown subpopulation of B cells in the human germinal center that is characterized by tyrosine phosphorylated transcriptional activator STAT5. These cells had an activated centrocyte phenotype and had abundant expression of BCL6 but low expression of PRDM1, both encoding transcriptional repression proteins.

The loss of PTEN allows TCR alphabeta lineage thymocytes to bypass IL-7 and Pre-TCR-mediated signaling.

The phosphatase and tensin homologue deleted on chromosome 10 (PTEN) negatively regulates cell survival and proliferation mediated by phosphoinositol 3 kinases. We have explored the role of the phosphoinositol(3,4,5)P3-phosphatase PTEN in T cell development by analyzing mice with a T cell-specific deletion of PTEN. Pten(flox/flox)Lck-Cre mice developed thymic lymphomas, but before the onset of tumors, they showed normal thymic cellularity.

Ep-CAM transfection in thymic epithelial cell lines triggers the formation of dynamic actin-rich protrusions involved in the organization of epithelial cell layers.

Thymic epithelium is organized in a highly connected three-dimensional network through which thymocytes differentiate. The molecular mechanisms underlying this organization are still unknown. In thymic medulla, a major site of tolerance induction, the development of the epithelial cell net is tightly regulated by the needs of thymocyte selection.