Immune cell trafficking to the islets during type 1 diabetes.

Inhibition of immune cell trafficking to the pancreatic islets during type 1 diabetes (T1D) has therapeutic potential, since targeting of T cell and B cell trafficking has been clinically effective in other autoimmune diseases. Trafficking to the islets is characterized by redundancy in adhesion molecule and chemokine usage, which has not enabled effective targeting to date. Additionally, cognate antigen is not consistently required for T cell entry into the islets throughout the progression of disease. However, myeloid cells are required to enable T cell and B cell entry into the islets, and may serve as a convergence point in the pathways controlling this process. In this review we describe current knowledge of the factors that mediate immune cell trafficking to pancreatic islets during T1D progression.

Cutting edge: functional role for proline-rich tyrosine kinase 2 in NK cell-mediated natural cytotoxicity.

Protein tyrosine kinase activation is one of the first biochemical events in the signaling pathway leading to activation of NK cell cytolytic machinery. Here we investigated whether proline-rich tyrosine kinase 2 (Pyk2), the nonreceptor protein tyrosine kinase belonging to the focal adhesion kinase family, could play a role in NK cell-mediated cytotoxicity. Our results demonstrate that binding of NK cells to sensitive target cells or ligation of beta2 integrins results in a rapid induction of Pyk2 phosphorylation and activation. By contrast, no detectable Pyk2 tyrosine phosphorylation is found upon CD16 stimulation mediated by either mAb or interaction with Ab-coated P815 cells. A functional role for Pyk2 in natural but not Ab-mediated cytotoxicity was demonstrated by the use of recombinant vaccinia viruses encoding the kinase dead mutant of Pyk2. Finally, we provide evidence that Pyk2 is involved in the beta2 integrin-triggered extracellular signal-regulated kinase activation, supporting the hypothesis that Pyk2 plays a role in the natural cytotoxicity by controlling extracellular signal-regulated kinase activation.

RAC1/P38 MAPK signaling pathway controls beta1 integrin-induced interleukin-8 production in human natural killer cells.

The MAP kinase (MAPK) p38 plays a key role in regulating inflammatory responses. Here, we demonstrate that beta1 integrin ligation on human NK cells results in the activation of the p38 MAPK signaling pathway, which is required for integrin-triggered IL-8 production. In addition, we identified some of the upstream events accompanying the beta1 integrin-mediated p38 MAPK activation, namely, the activation of the Rac guanine nucleotide exchange factor (GEF) p95 Vav, the small G protein Rac1, and the cytoplasmic kinases Pak1 and MKK3. Finally, we provide direct evidence that p95 Vav and Rac control the activation of p38 MAPK triggered by beta1 integrins.

Interleukin-2 gene transfer into human transitional cell carcinoma of the urinary bladder.

Transitional cell carcinoma of the bladder is one of the human cancers most responsive to immunotherapy, and local interleukin-2 (IL-2) production appears to be an important requirement for immunotherapy to be effective. In this study, we engineered two human bladder cancer cell lines (RT112 and EJ) to constitutively release human IL-2 by retroviral vector-mediated gene transfer. Following infection and selection, stable and consistent production of biologically active IL-2 was demonstrated at both the mRNA and the protein level. Morphology, in vitro growth rate and proliferation, as well as other cytokine gene mRNA or membrane adhesion receptor expression, were not altered in IL-2 transduced cells as compared to their parental or control vector-infected counterparts. Moreover, IL-2 engineered cells lost their tumorigenicity into nu/nu mice and the mechanism of rejection appeared to involve multiple host effector cell populations, among which a prominent role was played by neutrophils and radiosensitive cells. These findings may offer support to the development of an IL-2-based gene therapy approach to human bladder cancer.

Integrin-mediated ras-extracellular regulated kinase (ERK) signaling regulates interferon gamma production in human natural killer cells.

Recent evidence indicates that integrin engagement results in the activation of biochemical signaling events important for regulating different cell functions, such as migration, adhesion, proliferation, differentiation, apoptosis, and specific gene expression. Here, we report that beta1 integrin ligation on human natural killer (NK) cells results in the activation of Ras/mitogen-activated protein kinase pathways. Formation of Shc-growth factor receptor-bound protein 2 (Grb2) and Shc-proline-rich tyrosine kinase 2-Grb2 complexes are the receptor-proximal events accompanying the beta1 integrin-mediated Ras activation. In addition, we demonstrate that ligation of beta1 integrins results in the stimulation of interferon gamma (IFN-gamma) production, which is under the control of extracellular signal-regulated kinase 2 activation. Overall, our data indicate that beta1 integrins, by delivering signals capable of triggering IFN-gamma production, may function as NK-activating receptors.