CEACAM1 and the regulation of mucosal inflammation.

Inflammatory bowel disease (IBD) is characterized by unrestrained T-cell activation that results in the production of a variety of inflammatory cytokines and other mediators. Understanding the mechanisms of T-cell regulation is therefore of significant importance to IBD and other forms of dysregulated-mucosal inflammation. An area that is of significant interest are the cell autonomous mechanisms of T-cell regulation through proteins that have natural inhibitory functions when expressed on T lymphocytes. One such molecule is carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1). CEACAM1 is primarily an activation-induced cell-surface molecule that functions as a co-inhibitory receptor. Homophilic ligation of CEACAM1 on T cells leads to a signaling mechanism, which results in inhibition of a broad range T-cell functions. CEACAM1 therefore represents a new potential therapeutic target in the treatment of IBD.

Blockade of NKG2D signaling prevents the development of murine CD4+ T cell-mediated colitis.

It has been recently demonstrated that NKG2D is an activating costimulatory receptor on natural killer (NK) cells, natural killer T (NKT) cells, activated CD8(+) T cells, and gammadelta T cells, which respond to cellular stress, such as inflammation, transformation, and infection. Here we show that intestinal inflammation in colitic SCID mice induced by adoptive transfer of CD4(+)CD45RB(high) T cells is characterized by significant increase of CD4(+)NKG2D(+) T cells and constitutive expression of NKG2D ligands, such as H60, Mult-1, and Rae-1, by lamina propria CD11c(+) dendritic cells. Furthermore, treatment with nondepleting and neutralizing anti-NKG2D MAb after transfer of CD4(+)CD45RB(high) T cells into SCID mice significantly suppressed wasting disease with colitis, abrogated leukocyte infiltration, and reduced production of IFN-gamma by lamina propria CD4(+) T cells. These findings demonstrate that NKG2D signaling pathway is critically involved in CD4(+) T cell-mediated disease progression and suggest a new therapeutic target for inflammatory bowel diseases.

Epstein-barr virus (EBV) nuclear protein 2-induced disruption of EBV latency in the Burkitt's lymphoma cell line Akata: analysis by tetracycline-regulated expression.

The Burkitt's lymphoma (BL) cell line Akata retains the latency I program of Epstein-Barr virus (EBV) gene expression and cross-linking of its surface immunoglobulin G (IgG) by antibodies results in activation of viral replication. When EBV nuclear antigen 2 (EBNA2) was artificially expressed by a constitutive expression vector, the Cp EBNA promoter remained inactive and accordingly the latency III program was not induced. In contrast, expression of LMP2A and activity of the Fp lytic promoter were activated. Consistent with this Fp activity, the rate of spontaneous activation of the EBV replicative cycle was increased significantly, suggesting the possibility that EBNA2 can induce EBV replication. The efficiency of anti-IgG-induced activation of the viral replication was reduced in Akata cells expressing EBNA2. To obtain more direct evidence for EBNA2-induced activation of the EBV replicative cycle, this protein was next expressed by a tetracycline-regulated expression system. EBNA2 was undetectable with low doses (<0.5 microgram/ml) of tetracycline, while its expression was rapidly induced after removal of the antibiotic. This induced expression of EBNA2 was immediately followed by expression of EBV replicative cycle proteins in up to 50% of the cells, as shown by indirect immunofluorescence and immunoblot analysis. These results suggest an unexpected potential of EBNA2 to disrupt EBV latency and to activate viral replication.

Diffuse hemangiomatosis, coagulopathy and microangiopathic hemolytic anemia.

Described here is an autopsy case of a 30-year-old woman with systemic hemangiomatosis accompanied by coagulopathy and microangiopathic hemolytic anemia. She had hepato-splenomegaly, anemia, thrombocytopenia, prolonged prothrombin time and partial thromboplastin time, and fibrinogenopenia. A splenectomy was performed and a diffuse angioma of the spleen was found. Postmortem examination revealed cavernous hemangiomas and hemangioendotheliomatous lesions in the liver, bone marrow, intestine, and lymph nodes. Coagulation studies suggested that exacerbation of coagulopathy occurred due to Liniac (10MV X-ray) irradiation. Our observation raised the possibility that the irradiation might lead to chronic localized consumption coagulopathy, which was confined to the hemangioma, to acute disseminated types of intravascular coagulation.

Experimental studies on etiology of portal hypertension in allergic aspect.

To elucidate the mechanism of portal hypertension seen as a symptom of so-called Banti's syndrome (idiopathic portal hypertension), observation was made of rising of the portal pressure experimentally induced in sensitized rabbits. Intraintestinal injection of the same antigen as used for the sensitization resulted in elevation of the portal pressure. This phenomenon appears to be attributable to antigen-antibody reaction caused by the injected antigen absorbed from the intestine and entered thereby into the portal system while maintaining its antigenicity. From the phenomenon also, the site of the antigen-antibody reaction is estimated to be limited at least to the hepatic level. The portal pressure-rising phenomenon observed following intraintestinal introduction of antigen may suggest the possibility of entrance of the orally introduced antigen to the portal system, emphasizes importance of alimentary factors in the genesis of this syndrome.