miRNPs: a novel class of ribonucleoproteins containing numerous microRNAs

Gemin3 is a DEAD-box RNA helicase that binds to the Survival of Motor Neurons (SMN) protein and is a component of the SMN complex, which also comprises SMN, Gemin2, Gemin4, Gemin5, and Gemin6. Reduction in SMN protein results in Spinal muscular atrophy (SMA), a common neurodegenerative disease. The SMN complex has critical functions in the assembly/restructuring of diverse ribonucleoprotein (RNP) complexes. Here we report that Gemin3 and Gemin4 are also in a separate complex that contains eIF2C2, a member of the Argonaute protein family. This novel complex is a large approximately 15S RNP that contains numerous microRNAs (miRNAs). We describe 40 miRNAs, a few of which are identical to recently described human miRNAs, a class of small endogenous RNAs. The genomic sequences predict that miRNAs are likely to be derived from larger precursors that have the capacity to form stem-loop structures.     

Expression of CD83 in the murine immune system

CD83 is used as a marker for mature dendritic cells (DC) in man. We have developed a new monoclonal antibody (mAb), Michel-17, that specifically recognizes mouse CD83. We show that murine CD83 is expressed mainly on mature DC and on activated T cells. Histological analysis of serial spleen sections revealed a CD83 expression pattern resembling that of MIDC-8, a known murine DC marker molecule. In contrast to other costimulatory receptors, cross-linking of CD83 with the mAb Michel-17 on DC or T cells does not induce any activation signals. Our data describe for the first time the expression pattern of murine CD83, which is comparable to that of human CD83.The unique mAb Michel-17 will help to elucidate the biological functions of the CD83 molecule in more detail.     

Enhancement of immunogenicity of Jeg3 cells by ectopic expression of HLA-A*0201 and CD80

PROBLEM: The choriocarcinoma cell line Jeg3 suppresses immunity in vitro by secretion of soluble factors like leukemia inhibitory factor suppressing leukocyte activation. The cells lack expression of classical human leukocyte antigen (HLA)-A and -B alleles but express some HLA-C, and non-classical HLA-G and -E. Upon binding to killing inhibitory receptor on natural killer (NK) cells, HLA-G prevents activation of cytolytic activity. We investigated whether Jeg3 cells are capable of immune stimulation after complementation with classical HLA and T cell costimulatory signal CD80. METHOD OF STUDY: Jeg3 cells were transduced to express HLA-A*0201 and/or CD80. Parental Jeg3 or transfectants Jeg3-A2, Jeg3-CD80 or Jeg3-CD80-A2 were used to stimulate allogeneic resting and activated peripheral blood lymphocytes (PBL). The different cell lines were loaded with a HLA-A2-restricted Epstein-Barr virus (EBV) recall antigen peptide epitope and antigen presenting ability was examined. T cell lines specific for Jeg3 and transfectants were generated from HLA-A2 matched and nonmatched donors and compared for expansion, phenotypes and cytolytic activity. RESULTS: While all Jeg3 cell lines induced only marginal proliferation of resting T cells, phytohemagglutinin (PHA)-activated T cells were stimulated by CD80 or CD80-A2 expressing Jeg3. Only the transfectant Jeg3-CD80-A2 was capable of specific T cell stimulation by EBV recall antigen presentation. T cell lines of HLA-A2 non-matched donors stimulated with the Jeg3 transfectants showed significant expansion only when HLA-A2 and the costimulus CD80 were present. T cells from HLA-A2 positive donors did not expand significantly or differentially. No NK cells grew under any condition. In Jeg3-CD80-A2 stimulated T cells lines CD8+ cells expanded preferentially. These T cells exerted cytolytic activity toward all Jeg3 cell lines. CONCLUSION: Our data suggest that, in spite of immunosuppressive mechanisms, proliferative and cytolytic T cell responses are induced by Jeg3 cells when classical HLA- and/or costimulatory signals are present on the cells.     

CD97, but not its closely related EGF-TM7 family member EMR2, is expressed on gastric,pancreatic, and esophageal carcinomas

CD97 expression is related closely to the dedifferentiation and tumor stage in thyroid carcinomas. We systematically examined the role of CD97 and its closest relative, EMR2, in normal and malignant gastric, esophageal, and pancreatic tissue. The normal tissues were EMR2-, whereas CD97 was expressed slightly in the parietal cells of gastric mucosa and in exocrine pancreatic cells. Interestingly, intralobular and interlobular pancreatic ducts were CD97+. All tumors were EMR2-. CD97 was expressed by 44 of 50 gastric, 14 of 18 pancreatic, and 10 of 13 esophageal carcinomas. Of the 44 gastric cancers, 27 showed disseminated or scattered tumor cells at the invasion front with stronger CD97 expression than tumor cells located in solid tumor formations. There was no correlation between CD97 levels in the tumors or soluble CD97 in the serum samples and the clinicopathologic features of the patients. Taken together, significant numbers of gastric, esophageal, and pancreatic carcinomas are CD97+, whereas its homolog, EMR2, does not have any role in such tumors.     

Analysis of the coxsackievirus B-adenovirus receptor gene in patients with myocarditis or dilated cardiomyopathy

Myocarditis and dilated cardiomyopathy (DCM) are common causes of morbidity and mortality in children and adults, most commonly due to infection with coxsackievirus B or adenovirus. Increased expression of the common human coxsackievirus B-adenovirus receptor (CAR) has been reported in patients with DCM. We investigated the CAR gene in patients with acquired or familial myocarditis/DCM for mutations/polymorphisms. Several polymorphisms or intronic substitutions, distant from the intron-exon boundaries, were identified but no mutations. Based upon these data it appears that CAR gene mutations are not a major host determinant in the development of myocarditis and DCM.     

Detecting danger--or just another odorant? Olfactory sensitivity for the fox odor component 2,4,5-trimethylthiazoline in four species of mammals

2,4,5-trimethylthiazoline (TMT) is a volatile component of the anal gland secretion of the red fox and elicits behavioral and physiological fear responses in the rat. Using instrumental conditioning paradigms, we determined olfactory detection thresholds for TMT in three rats, a natural prey species of the red fox, and compared their performance to that of three squirrel monkeys, three spider monkeys and four pigtail macaques, all non-prey species of the red fox. We found that the rats were able to discriminate concentrations between 0.04 and 0.10 ppt (parts per trillion) of TMT from the odorless solvent which is by far the lowest olfactory detection threshold for an odorant reported in rats so far. In contrast, the spider monkeys needed 0.14-1.38 ppb (parts per billion), the pigtail macaques 0.41-4.07 ppb, and the squirrel monkeys 4.07-13.80 ppb to detect TMT which does not rank among the lowest olfactory thresholds reported for these three primate species. Thus, these results support the assumption that the behavioral relevance of an odorant may be an important determinant of a species' olfactory sensitivity.     

Betamethasone effects on fetal sheep cerebral blood flow are not dependent on maturation of cerebrovascular system and pituitary–adrenal axis

Synthetic glucocorticoids are administered to pregnant women in premature labour to accelerate fetal lung maturation at a time when fetal cerebrovascular and endocrine systems are maturing. Exposure to glucocorticoids at 0.8–0.9 of gestation increases peripheral and cerebrovascular resistance (CVR) in fetal sheep. We examined whether the increase of CVR and its adverse effect on cerebral blood flow (CBF) depend on the current level of maturation of the pituitary–adrenal axis and the cerebrovascular system. Using fluorescent microspheres, regional CBF was measured in 11 brain regions before and 24 h and 48 h after the start of 3.3 μg kg⁻¹ h⁻¹ betamethasone ( n = 8) or vehicle ( n = 7) infusions to fetal sheep at 0.73 of gestation. Hypercapnic challenges were performed before and 24 h after the onset of betamethasone exposure to examine betamethasone effects on cerebrovascular reactivity. Betamethasone exposure decreased CBF by approximately 40% in all brain regions after 24 h of infusion ( P < 0.05). The decline in CBF was mediated by a CVR increase of 111 ± 16% in the cerebral cortex and 129 ± 29% in subcortical regions ( P < 0.05). Hypercapnic cerebral vasodilatation and associated increase in CBF were blunted ( P < 0.05). Fetal CBF recovered after 48 h of betamethasone administration. There were no differences in glucocorticoid induced CBF and CVR changes compared with our previous findings at 0.87 of gestation. We conclude that the cerebrovascular effects of antenatal glucocorticoids are independent of cerebrovascular maturation and preparturient increase in activity of the fetal pituitary–adrenal axis.     

IP-10 and type 1 diabetes: a question of time and location

Chemokines are key signal molecules that attract cells of the host immune system to the site of a potential threat. Virus infections usually induce a massive chemokine and cytokine burst and therefore recruit a large plethora of leukocytes to the site of infection with the goal to restrict and abrogate viral spread. The down side of this massive excitation of the human defense system is non-specific activation of potentially self-reactive lymphocytes. Coupled with an antigen-specific event, for example molecular mimicry between host components and viral proteins, autoimmunity might be the consequence in susceptible individuals. However, activated immune components with autoaggressive potential must find their target and must remain in one site sufficiently long in order to cause chronic tissue damage. In this review we will focus on the influence of the chemokine IP-10 (CXCL10) on the trafficking of autoaggressive cells during the immunopathogenesis of type 1 diabetes (T1D) and explain why IP-10 can have a dual effect on T1D depending on time and location of expression.