2B4-mediated activation of human natural killer cells

2B4 is a member of the CD2 subset of the immunoglobulin superfamily of cell surface receptors. Other members of this family include CD2, CD48, CD58, CD84, signaling lymphocytic activation molecule and Ly-9. Some of these molecules are activating structures expressed by natural killer cells and T cells. We have recently cloned and characterised the human homologue of 2B4 and found that the cytoplasmic domain of 2B4 can interact with SAP, a signaling adaptor protein that is mutated in the immunodeficiency X-linked lymphoproliferative disease (XLP). Additionally, the natural ligand of 2B4 has been identified as CD48. These findings have facilitated the investigation of the functional role of this receptor-ligand pair, and associated signal transduction pathways, on immune cells. In this study, it was found that the interaction between 2B4 on effector cells and CD48 on target cells induced NK-cell activation, as evidenced by increased cytotoxicity and secretion of IFN-gamma. The responses induced by ligation of 2B4 could be reduced by the co-ligation of inhibitory receptors expressed by NK cells, demonstrating that activation signals delivered via 2B4 can be regulated by the action of certain inhibitory receptors. Because the signalling pathway of 2B4 involves SAP, it is possible that 2B4-mediated NK-cell activation may be compromised in patients with XLP due to mutations in SAP. This may contribute to the phenotype and progression of this disease.     

NKG2D ligands: unconventional MHC class I-like molecules exploited by viruses and cancer

Our best teachers in revealing the importance of immune pathways are viruses and cancers that have subverted the most prominent pathways to escape from immune recognition. Viruses and cancer impair antigen presentation by classical MHC class I to escape adaptive immunity. The activating receptor NKG2D and its MHC class I-like ligands are other recently defined innate and adaptive immune pathways exploited by viruses and cancer. This review discusses recent advances in the understanding of how NKG2D, expressed on innate immune cells including natural killer cells, gammadelta+ T cells and macrophages, and adaptive immune cells such as CD8+ T cells, recognize stress-induced, MHC class I-like, self-ligands. Moreover, we describe how viruses and cancer have developed strategies to evade this recognition pathway.     

Innovative approaches in governance: a case study of the Greater Southeast Healthcare System

Washington, D.C.'s Greater Southeast Healthcare System is like a spinning top--balanced by internal energy and driven by external forces. Those forces, the voices of the system's community, have provided Greater Southeast with direction and governance that have brought the system national recognition as well as an agenda for change. Even more important, they have resulted in services that have grown deep roots in the community.     

Peptide vaccination using nonionic block copolymers induces protective anti-viral CTL responses.

High molecular weight nonionic block copolymers have been developed as vaccine adjuvants. We employed these adjuvants in water-in-oil emulsion and multiple emulsion formulations with a synthetic peptide-based antigen vaccine to test their ability to prime anti-viral CD8(+) T cell responses. Vaccines were made using the H-2(d)-restricted immunodominant peptide from lymphocytic choriomeningitis virus (LCMV), NP118-126, and administered to BALB/c ByJ (H-2(d)) mice. Peptide-containing emulsions were able to induce NP118-126 specific CTL and IFN-gamma secreting CD8(+) T cells in the vaccinated mice and these responses were maintained for at least 90 days post immunization. At all times, the responses induced by the copolymer formulations were equal to, or better than, formulations based on incomplete Freund's adjuvant (IFA). In addition, the responses induced by prophylactic vaccination using the multiple emulsion formulation resulted in accelerated viral clearance following infection with a strain of LCMV (clone 13) that causes a persistent infection in na?ve adult mice. These results indicate that peptide vaccination using a formulation based on high molecular weight nonionic block copolymer in a simple water-in-oil or a multiple emulsion format can induce virus-specific CD8(+) T cell responses and confer protection sufficient enough to prevent the establishment of a persistent infection.     

Combination of fludarabine and mitoxantrone in untreated stages III and IV low-grade lymphoma: S9501.

PURPOSE: To determine the efficacy of combination fludarabine and mitoxantrone (FN) in untreated stages III and IV low-grade lymphoma. The major end point was to estimate progression-free survival (PFS) in all eligible patients. PATIENTS AND METHODS: Seventy-eight eligible patients were registered. Chemotherapy courses were administered every 4 weeks with mitoxantrone 10 mg/m2 on day 1 and fludarabine 25 mg/m2 on days 1, 2, and 3 for a total of six to eight cycles. Pneumocystis carinii prophylaxis was required. RESULTS: Seventy-three patients (94%) attained an objective response. Complete remission was demonstrated in 34 patients (44%) and partial remission was demonstrated in 39 patients (50%). With a median follow-up time of 5.5 years, the median PFS was 32 months, with a 4-year PFS rate of 38%. Median survival has not been reached and 88% of all patients are alive at 4 years. The application of the International Prognostic Index and serologic staging showed significant differences in PFS in all risk groups, whereas overall survival was markedly worse for the highest-risk group in either prognostic model. Three prior Southwest Oncology Group trials using a regimen of cyclophosphamide, doxorubicin, vincristine, and prednisone or a combination of prednisone, vincristine, methotrexate, cytarabine, cyclophosphamide, etoposide, nitrogen mustard, vincristine, procarbazine, and prednisone in similar patient populations demonstrated comparable clinical outcome, although the 4-year survival for FN was better. FN was well tolerated, but mild to severe reversible myelosuppression was noted. Other complications were rare. CONCLUSION: FN is an effective, safe chemotherapy combination for patients with advanced-stage, low-grade lymphoma. Clinical outcomes were comparable to prior published data using anthracycline-based regimens.     

Diagnosis of pulmonary embolism: Ventilation perfusion scintigraphy versus helical computed tomography pulmonary angiography

The present study compared the accuracy of ventilation perfusion scintigraphy (VQS) and CT pulmonary angiography (CTPA) for the diagnosis of pulmonary embolism. This was a prospective observational study of 112 patients with suspected pulmonary embolism (PE) who could be studied with both investigations within 24 h. Results were compared to final diagnosis at completion of 6-month follow up, using receiver operating characteristic (ROC) analysis. Pulmonary embolism was diagnosed in 27 referred patients (24%). The sensitivity and specificity of VQS and CTPA were similar to that reported from the literature. A normal VQ scan had the highest negative predictive value (100%), while a high-probability VQ scan had the highest positive predictive value (92%). There was no overall difference (area under the ROC curve (AUC)) between VQS (AUC (95% CI) = 0.82 (0.75,0.89)) and CTPA (AUC = 0.88 (0.81,0.94)) for the diagnosis of PE. Among patients with abnormal chest X-rays, CTPA (AUC 0.90 (0.83,0.97)) appeared somewhat better than VQS (AUC 0.78 (0.68,0.88)) but this difference did not reach statistical significance. In this instance, CTPA is at least as accurate as VQS and may provide an opportunity to make alternative diagnoses.     

Assessment of Hageman factor activation in human plasma: quantification of activated Hageman factor-C1 inactivator complexes by an enzyme- linked differential antibody immunosorbent assay

An enzyme-linked immunosorbent assay has been developed for the quantitation of activated Hageman factor-C1 inactivator (HF-C1 INH) complexes. Addition of increasing quantities of either of the major forms of activated Hageman factor (HFa or HFf) to normal plasma or to Hageman factor-deficient plasma leads to a dose-dependent increase in activated HF-C1 INH complexes. As little as 0.5 micrograms/mL of activated HF added to plasma can be detected, corresponding to activation of approximately 2% of plasma HF. The sensitivity of the assay is increased at least tenfold when complexes are formed in HF- deficient plasma, indicating competition between unactivated HF and activated HF-C1 INH complexes for binding to the antibody. Specificity is demonstrated in that addition of activated HF to hereditary angioedema plasma yields less than 1% of the activated HF-C1 INH complex formation obtained with normal plasma. Kaolin activation of HF- deficient plasma yields no detectable complex formation. Kaolin activation of prekallikrein-deficient plasma demonstrates a time- dependent increase in formation of activated HF-C1 INH complex consistent with the ability of HF in this plasma to autoactivate as the time of incubation with the surface is increased. Kaolin treatment of high-molecular weight (HMW) kininogen-deficient plasma yields an even more profound abnormality in the rate of formation of activated HF-C1 INH complexes reflecting the complex role of HMW kininogen in the initiation of contact activation. Although addition of corn inhibitor to plasma prevents activated HF-C1 INH complex formation, it does not inhibit activated HF sufficiently fast to prevent prekallikrein activation.     

Activator of G protein signaling 3 null mice: I. Unexpected alterations in metabolic and cardiovascular function

Activator of G protein signaling (AGS)-3 plays functional roles in cell division, synaptic plasticity, addictive behavior, and neuronal development. As part of a broad effort to define the extent of functional diversity of AGS3-regulated-events in vivo, we generated AGS3 null mice. Surprisingly, AGS3 null adult mice exhibited unexpected alterations in cardiovascular and metabolic functions without any obvious changes in motor skills, basic behavioral traits, and brain morphology. AGS3 null mice exhibited a lean phenotype, reduced fat mass, and increased nocturnal energy expenditure. AGS3 null mice also exhibited altered blood pressure control mechanisms. These studies expand the functional repertoire for AGS3 and other G protein regulatory proteins providing unexpected mechanisms by which G protein systems may be targeted to influence obesity and cardiovascular function.     

Low frequency of p53 mutations observed in a diverse collection of primary hepatocellular carcinomas.

Recent studies of the p53 tumor suppressor locus (designated TP53) in primary hepatocellular carcinoma (PHC) have identified a high frequency of codon 249 mutations. Due to the geographic location from which the samples were obtained and the substitution observed, the mutation was suggested to be attributable to aflatoxin B1 (AFB1) exposure. To determine the generality of this phenomenon, we have examined PHC tissues from 107 geographically and ethnically diverse sources. The frequency of p53 gene mutations was evaluated by using PCR/restriction-digest methods, GC-clamp (G+C-rich sequence) denaturing gradient gel electrophoresis, and DNA sequencing. The mutation rate observed in tumors from high-AFB1-exposure regions (25%) was more than double the rate observed in low-exposure regions (12%) but lower than the 50% frequency previously reported. Codon 249 mutations occurred at a much lower frequency than previously reported (2 of 107 samples examined). These results suggest that changes in DNA encoding p53 may not represent primary oncogenic effects but instead represent genetic changes related to tumor progression. High AFB1 levels may facilitate the generation of these progressional changes, but not by inducing a specific p53 gene mutation at codon 249 as previously reported.