CD4+CD25+ regulatory/suppressor T cells prevent allogeneic fetus rejection in mice

Recent evidences indicate that naturally occurring CD4+CD25+ regulatory/suppressor T cells (T(reg)) regulate not only autoimmunity, but also alloreactivity. In mice, they notably control tolerance to allogeneic transplants and graft-versus-host disease after allogeneic hematopoietic stem cell transplantation. Here, we studied the role of T(reg) in maternal tolerance to fetuses, i.e. natural semi-allogeneic grafts. We show that semi-allogeneic pregnancies in mice induce an expansion of T(reg), but not of activated CD4+ and CD8+ T cells, in para-aortic lymph nodes draining fetal antigens. The treatment of female mice with an anti-CD25 antibody before mating results in depletion of T(reg) and expansion of activated CD4+ and CD8+ T cells solely in the draining lymph nodes, ultimately leading to fetus rejection. These observations were not made in the context of syngeneic pregnancies. Thus, T(reg) play a major role in maternal-fetal tolerance.     

Contribution of microdissection for the detection of microsatellite instability in colorectal cancer

The determination ofmicrosatellite instability (MSI) is an important step in the identification of familial colorectal cancer such as hereditary nonpolyposis colon cancer. It could also be of interest in the therapeutic management of sporadic cancer. International criteria for the determination of MSI have been published, recommending the use of microdissection. The aim of this work was to evaluate the impact of contaminant normal DNA in tumor samples for MSI assessment in colorectal cancer using a microdissection technique. We performed a comparative analysis of the microsatellite status between total DNA (DNA extracted from whole tumor samples) and microdissected DNA in 3 different regions from 23 cases of colorectal cancer. Six microsatellites were amplified using fluorescent polymerase chain reaction. We analyzed 9 cases with MSI and 14 cases without instability, with similar results between total DNA and microdissected DNA. Moreover, within a same tumor, the MSI phenotype was observed regardless of the region analyzed. Thus, this work shows the reproducibility of the MSI phenotype throughout a tumor. However, we observed a regional heterogeneity of the MSI profile, consisting of variations in the number and the size of unstable alleles within different regions. This result reflects the genetic heterogeneity of colorectal cancer with MSI. In the 14 cases without instability, we observed an increase of more than 60% in the loss of heterozygosity detection rate after microdissection. Thus, this work confirms the contribution of microdissection for loss of heterozygosity assessment.     

Identification of virulence genes linked with diarrhea due to atypical enteropathogenic Escherichia coli by DNA microarray analysis and PCR

The role of atypical enteropathogenic Escherichia coli (EPEC) in childhood diarrhea is controversial. The aim of the present study was to search for genes linked with diarrhea in atypical EPEC strains from a case-control study among Norwegian children. Using DNA microarray analysis, genomic DNAs from strains isolated from children with (n = 37) and without (n = 20) diarrhea were hybridized against 242 different oligonucleotide probes specific for 182 virulence genes or markers from all known E. coli pathotypes. PCR was performed to test the strains for seven putative virulence genes not included in the microarray panel. The OI-122 gene efa1/lifA was the gene with the strongest statistical association with diarrhea (P = 0.0008). Other OI-122 genes (set/ent, nleB, and nleE) and genes with other locations (lpfA, paa, ehxA, and ureD) were also associated with diarrheal disease. The phylogenetic marker gene yjaA was negatively associated with diarrhea (P = 0.0004). Atypical EPEC strains could be classified in two main virulence groups based on their content of OI-122, lpfA, and yjaA genes. Among children with diarrhea, atypical EPEC isolates belonging to virulence group I (OI-122 and lpfA positive, yjaA negative) were the most common, while the majority of isolates from healthy children were classified as virulence group II strains (OI-122 negative, lpfA and yjaA positive; P < 0.001). In conclusion, using DNA microarray analysis to determine the virulence gene profile of atypical EPEC isolates, several genes were found to be significantly associated with diarrhea. Based on their composition of virulence genes, the majority of strains could be classified in two virulence groups, of which one was seen mainly in children with diarrhea.     

First detection of the Ambler class C 1 AmpC beta-lactamase in Citrobacter freundii by a new, simple double-disk synergy test

We report on the first detection of an AmpC-type Ambler class C 1 (ACC-1) beta-lactamase in Citrobacter freundi isolated from a patient also harboring ACC-1-producing Escherichia coli and Klebsiella pneumoniae. We propose a simple cefoxitin-based double-disk synergy test (DDST) for the specific detection of ACC-1 in members of the family Enterobacteriaceae, including natural AmpC producers, in association with a cloxacillin-based DDST as a first-line AmpC-type beta-lactamase screening test.     

Emergence and outbreaks of CTX-M beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae strains in a Tunisian hospital

Sixty-two isolates of Enterobacteriaceae (35 Escherichia coli and 27 Klebsiella pneumoniae isolates) producing CTX-M-type beta-lactamases were collected between March 2000 and June 2003 in different wards of Charles Nicolle Hospital in Tunis (Tunisia). Sequencing identified the bla(CTX-M-15) determinant in 55 isolates and bla(CTX-M-16) in 7 isolates. The CTX-M-15-producing strains were isolated in several wards and consisted mainly of two successive clonal groups of E. coli and a major clonal group of K. pneumoniae. The second clonal group of E. coli belonged to phylogenetic group B2 and harbored more virulence factors than the first clonal group. Among the 22 transconjugants or electroporants obtained with selected E. coli and K. pneumoniae CTX-M-15-producing strains, a predominant plasmid restriction pattern was obtained with 17 isolates. The four CTX-M-16-producing strains of E. coli yielded the same pulsed-field gel electrophoresis (PFGE) pattern, while the three CTX-M-16-producing strains of K. pneumoniae yielded two different PFGE patterns. All of the CTX-M-16-producing isolates were recovered in the pediatric ward and had the same plasmid restriction pattern.     

Photoinduced electron flow in a self-assembling supramolecular extension cable

We report the design, bottom-up construction, characterization, and operation of a supramolecular system capable of mimicking the function played by a macroscopic electrical extension cable. The system is made up of a light-powered electron source, an electron drain, and a cable as the molecular components programmed to self-assemble by means of two distinct plug/socket junctions. Such connections are reversible and can be operated independently by orthogonal chemical inputs. In the source-connector-drain supermolecule, photoinduced electron transfer from source to drain occurs, and it can be switched off by dual-mode chemically controlled disassembling of the molecular components.