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Biomedical subjects

Amos Cohen

Publications and source records attributed to Amos Cohen.

9 recordsLinked to original sources
PubMed2006

Mutations in the RNA component of RNase mitochondrial RNA processing might cause Omenn syndrome.

BACKGROUND: Omenn syndrome is a variant of severe combined immunodeficiency disease, which most prominently presents with erythroderma, eosinophilia, and susceptibility to various pathogens. Mutations in the nucleases of recombination activating genes 1 and 2 (RAG1/RAG2) or Artemis were found in some, but not all, patients with Omenn syndrome. We identified 2 patients who presented with clinical features consistent with Omenn syndrome but had no mutations in RAG or Artemis. Both patients also had cartilage-hair hypoplasia (CHH). OBJECTIVES: We sought to define the molecular basis and characterize the features of severe combined immunodeficiency and Omenn syndrome in these patients. METHODS: We have studied humoral and cellular immunity using standard assays. T-cell repertoire was investigated by quantitating Vbeta families. The RNase mitochondrial RNA processing (RMRP) RNA gene was sequenced by using standard techniques. RESULTS: Sequence analysis of the RMRP RNA gene showed that each patient had an insertion-duplication on one allele and a point mutation on the other allele. These point mutations were novel, and they might be related to the unusual presentation of Omenn syndrome in addition to CHH in these patients. Indeed, analysis of the thymus showed residual mature T lymphocytes. This leaky thymus might be responsible for the skewed release of some T-cell clones into the circulation, which might trigger the phenotype of Omenn syndrome. CONCLUSION: We have demonstrated that mutations in the RMRP RNA gene might be associated with Omenn syndrome. CLINICAL IMPLICATIONS: This discovery will aid clinicians in the early recognition and treatment of CHH-associated Omenn syndrome.

Base Sequence↗
PubMed2006

Erythropoietin treatment in advanced multiple myeloma is associated with improved immunological functions: could it be beneficial in early disease?

Erythropoietin (Epo) is the main growth regulator of red blood cells, and recombinant human erythropoietin (rHuEpo) is thus used in clinical practice for the treatment of anaemia, primarily in kidney disease and cancer. rHuEpo treatment was found to be associated with prolonged survival of multiple myeloma (MM) patients. This clinical observation was then supported by studies on murine myeloma models. It thus appeared that rHuEpo had an anti-myeloma effect, causally related to an immunomodulatory function of rHuEpo. The present study investigated whether rHuEpo-treated MM patients acquire improved immunological functions. Treatment with rHuEpo, prescribed for anaemia that occurs in advanced disease, was associated with effects on a variety of immunological parameters and functions. This was expressed in an actual normalisation of the CD4:CD8 cell ratio, enhanced T cell phytohaemagglutinin-mediated activation and proliferation potential, T cell expression of the costimulatory CD28 and inhibitory CTLA-4 molecules, as well as reduced interleukin-6 serum values to normal levels. Furthermore, it was demonstrated that immunological abnormalities manifest in patients even in the early stages of MM. Our findings thus suggest that rHuEpo treatment might be effective in the early stages of MM, before anaemia develops. It is expected that this would boost the immune system, consequently achieving an anti-myeloma function; affecting disease progression and improving the prognosis.

Aged↗
PubMed2004

Effect of IGF-1 on the balance between autophagy of dysfunctional mitochondria and apoptosis.

Mutations in mitochondrial DNA (mtDNA) cause excessive production of mitochondrial reactive oxygen species (ROS) and shorten animal life span. We examined the mechanisms responsible for removal of mitochondria with deleterious mtDNA mutations by autophagy. Incubation of primary cells and cell lines in the absence of serum promotes autophagy of mitochondria with deleterious mtDNA mutations but spares their normal counterparts. The effect of serum withdrawal on the autophagy of dysfunctional mitochondria is prevented by the addition of IGF-1. As a result of the elimination of mitochondria with deleterious mutations, excessive ROS production, characteristic of dysfunctional mitochondria, is greatly reduced. Mitochondrial autophagy shares a common mechanism with mitochondrial-induced cell apoptosis, including mitochondrial transition pore formation and increased ROS production.

Apoptosis↗
PubMed2004

Platelet function and its clinical significance in the myelodysplastic syndromes.

The current study was aimed at investigating platelet function in MDS and its clinical significance. There were 23 patients with untreated MDS at presentation, including refractory anemia (RA), RA with ringed sideroblasts, RA and excess blasts and chronic myelomonocytic leukemia RAEBt. The mean platelet count was 167.9 x 109/L. Patients with a platelet count less than 70 x 109/l were excluded. The mean bleeding time (BT) was 2.7 min. Only four MDS patients had BT longer than the normal 1-4 min range. Platelet aggregation (PA) was studied with epinephrine (Epi), ADP, arachidonic acid (AA), ristocetin and collagen. Overall, 16 (70%) patients had PA abnormality, 65% had impaired Epi-induced PA, 57% demonstrated reduced ADP-induced PA. AA, ristocetin and collagen was decreased PA in 48, 22 and 17%, respectively. Five patients (22%) demonstrated spontaneous PA. Only seven patients (30%) were found to have normal PA with all five inducers. Six (26%) patients had spontaneous mild bleeding and all six bleeding MDS patients demonstrated at least one abnormal platelet function. The only bleeding patient with all five PA tests normal demonstrated prolonged BT. In the present study of 23 newly diagnosed MDS patients, PA abnormalities were relatively common, the BTs were usually normal, and bleedings were relatively uncommon and mild at platelet count between 70 and 397 x 109/l.

Adenine Nucleotides↗
PubMed2004

Fulminant intravascular lymphoma presenting as fever of unknown origin.

Intravascular large cell lymphoma (IVLL) is a rare neoplasm characterized by the proliferation of malignant lymphoid cells within the lumens of small to medium-sized blood vessels. The central nervous system, skin, and endocrine systems are most commonly involved. IVLL may disseminate to the heart, pancreas, liver, spleen, kidneys, and adrenal glands. We report a 52-year-old patient who was admitted for fever of unknown origin for 3 weeks, jaundice and abnormal liver function tests. Fever, high levels of bilirubin, severe anemia, thrombocytopenia, and a very fulminant course characterized the clinical picture. Although bone marrow involvement is quite rare, the diagnosis of IVLL in this patient was done by bone marrow biopsy. The patient was treated with CHOP protocol and received the first course but the aggressive disease led to the patient's death.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Treatment of resistant thrombotic thrombocytopenic purpura with rituximab and cyclophosphamide.

Thrombotic thrombocytopenic purpura (TTP) is an uncommon acquired disease in adults, especially young women, characterized by fever, neurologic manifestations, microangiopathic hemolytic anemia, thrombocytopenia, and renal dysfunction. Treatment with plasmapheresis has increased the survival rate from 10% to greater than 90%. Still, a subset of patients with resistant TTP fail to respond to plasmapheresis or remain dependent on this procedure. We report such a patient who was successfully treated with rituximab and cyclophosphamide. She has now been disease free for more than 6 months. This novel treatment modality for TTP has been described for only a few patients. A well-controlled clinical trial is warranted to determine the role and place of this therapeutic approach in the management of TTP.

Adult↗
PubMed2003

Role of MHC class I in immune surveillance of mitochondrial DNA integrity.

Mitochondrial DNA is subject to increased rates of mutations due to its proximity to the source of reactive oxygen species. Here we show that increased MHC class I (MHC I) expression serves to alert the immune system to cells with mitochondrial mutations. MHC I is overexpressed in fibroblasts with mitochondrial dysfunction from patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes and in lymphocytes from purine nucleoside phosphorylase-deficient immune-deficient mice with mitochondrial DNA deletions. Consistent with a role of MHC I in the elimination of cells containing mitochondrial DNA mutations, mice deficient in MHC I accumulate mitochondrial DNA deletions in various tissues. These observations in both mice and humans suggest a role for the immune system in preventing reversion of mitochondrial DNA back into a parasitic state following deleterious mutations affecting mitochondrial oxidative phosphorylation.

Animals↗
PubMed2002

Phorbol esters and cAMP differentially regulate the expression of CD4 and CD8 in human thymocytes.

BACKGROUND: Intrathymic development and selection of the T lymphocyte repertoire is restricted by the interactions of the T cell antigen receptor and CD4 or CD8 co-receptors with self major histocompatibility complex molecules. Positive or negative selection depends on a tight regulatory control of CD4 and CD8 expression. Determining the intracellular signals that differentially regulate the expression of CD4 and CD8 is important to understand the mechanisms that are implicated in selection of single positive CD4+CD8- or CD4-CD8+. RESULTS: The present study shows that stimulation of human thymocytes by phorbol esters or cAMP result in a differential regulation of CD4 and CD8 expression, both at the mRNA and cell surface glycoprotein level. CONCLUSIONS: The differential regulation of CD4 and CD8 gene expression suggests that the selective activation of protein kinase C (PKC) and cAMP-dependent protein kinases (PKA) may be required for the selection of single positive CD4+CD8- and CD4-CD8+ cells during Intrathymic differentiation.

CD4 Antigens↗