In Brief

Lymphocyte Migration

Selective imprinting of gut-homing T cells by Peyer's patch dendritic cells. Mora, J. R. et al. Nature 424, 88–93 (2003)

The capacity of activated effector and memory T cells to migrate preferentially to tissues that are connected to the lymphoid organs in which they first encountered antigen has been known for some time. But how is this homing ability conferred on the T cells? For gut-homing T cells, von Andrian and colleagues now show that Peyer's-patch dendritic cells (DCs) are the cells that confer this homing capacity. Only DCs from the Peyer's patches could induce high levels of expression of the integrin α4β7 and the chemokine receptor CCR9, which are essential for homing of T cells to the small intestine. Whether this imprinting is an instructive or selective process remains to be determined.

Tumour Immunology

Stat5 synergizes with T cell receptor/antigen stimulation in the development of lymphoblastic lymphoma. Kelly, J. A. et al. J. Exp. Med. 198, 79–89 (2003)

This study shows the oncogenic potential of dysregulated expression of STAT5a or STAT5b. Signal transducer and activator of transcription (STAT) proteins are important components of many signalling pathways that are induced by cytokines and growth factors, and they have also been implicated in oncogenesis. In this study, Kelly et al. investigated the effect of overexpression of non-activated Stat5a or Stat5b in the lymphoid compartment. Expression of a Stat5a or Stat5b transgene resulted in the development of thymic T-cell lymphoblastic lymphomas. The rate of malignant transformation was increased by antigenic or adjuvant stimuli, or by the introduction of T-cell receptor transgenes.

T-cell Development

The Runx1 transcription factor inhibits the differentiation of naive CD4⁺ T cells into the T_H2 lineage by repressing GATA3 expression. Komine, O. et al. J. Exp. Med. 198, 51–61 (2003)

The transcription factor RUNX1 (also known as acute myelogenous leukaemia protein 1, AML1) is involved in the control of haematopoiesis and in leukaemogenesis. The differentiation of naive CD4⁺ T cells into T helper (T_H) cells is controlled by a combination of transcription factors and here, the authors investigated the role of RUNX1 in this process. Naive CD4⁺ T cells from transgenic mice that express a dominant interfering form of Runx1 showed enhanced production of the T_H2-type cytokine interleukin-4 and enhanced T_H2-cell development. By contrast, overexpression of Runx1 blocked the development of naive CD4⁺ T cells into T_H2 cells and inhibited the expression of the transcription factor GATA3. So, by inhibiting GATA3 expression, RUNX1 acts as a negative regulator of T_H2-cell differentiation.