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.     

Behavioural strategies used by the hookworms Necator americanus and Ancylostoma duodenale to find, recognize and invade the human host

The infective third-stage larvae of the hookworms Necator americanus and Ancylostoma duodenale infect their human hosts by active skin invasion, but A. duodenale is in addition capable of oral infection. The behaviour of the larvae when crawling on surfaces has already been described. Here we analyse in various in vitro systems the other behavioural invasion phases: activation, penetration, and orientation within the host. The larvae normally remained in a motionless, energy-saving, resting posture. An activation to sinusoidal locomotion was stimulated in both species by similar cues such as touch, vibration, water currents, heat, light, and chemicals. Human breath in addition stimulated searching and waving (nictating) behaviour, which facilitates a change-over to the host. Activating cues in air streams were warmth and moisture; CO₂ activated only in combination with warmth and/or moisture. Penetration behaviour in both species was stimulated by warmth and skin extracts. The stimulating components of skin extracts were fatty acids, but their stimulating characteristics differed from those inducing schistosome cercarial skin penetration. After penetration into agar substrates, both species showed thermo-orientation, but only A. duodenale followed gradients of serum. The directing serum cues were not amino acids and glucose (the supposed cues for schistosome blood vessel localization), but Ringers solution attracted the larvae. The host-finding and host-invasion behaviour of both hookworm species is well adapted to the invasion of the human skin, and there seems to be no particular adaptation of A. duodenale behaviour to the oral infection mode. Hookworm host-finding behaviour is not as complex as that of schistosome cercariae but seems well adapted to the ecological conditions in the transmission sites.     

Rapid identification of female carriers of DMD/BMD by quantitative real-time PCR

Recently developed PCR systems offer online-monitoring of amplification and allow simple and reliable DNA quantification. We have used the LightCycler system to develop a simple and rapid method for direct identification of female carriers of deletions and duplications in the dystrophin gene. The challenge resides in the ability to identify the presence of a deleted or duplicated allele over the background contributed by the normal allele. Quantification is based on the determination of the ratio between potentially deleted/duplicated dystrophin exons and non-deleted/-duplicated reference exons using the unspecific dsDNA-dye SYBRgreen I. In a retrospective study, we evaluated our method in female relatives of DMD/BMD patients with known carrier status by comparative analysis of deleted or duplicated versus non-deleted/-duplicated exons. Carrier status was accurately attributed in 100% of cases, the mean ratios being 0.52+/-0.12 for deletion carriers (expected value: 0.5) and 1.56+/-0.18 for duplication carriers (expected value: 1.5) vs. 1.022+/-0.17 for non-carriers (expected value: 1.0). The method proved to be simple, rapid, reliable, and cost-effective. It may be used for direct determination of deletions/duplications in potential DMD/BMD carriers and may easily be adapted for other genetic conditions involving deletions and duplications.     

Hypothetical LOC387715 is a second major susceptibility gene for age-related macular degeneration, contributing independently of complement factor H to disease risk

Age-related macular degeneration (AMD) is a multifactorial disease and a prevalent cause of visual impairment in developed countries. Risk factors include environmental components and genetic determinants. The complement factor H (CFH) has been the first major susceptibility gene for AMD identified within 1q32. Here, we focused on a second region of interest in 10q26 where a recent meta-analysis revealed strongest evidence for linkage to AMD at a genome-wide significance level. Within an interval of 22 Mb, we have analyzed 93 single nucleotide polymorphisms for allelic association with AMD in two independent case-control cohorts of German origin (AMD(combined) n=1166; controls(combined) n=945). Significant association was found across a 60 kb region of high linkage disequilibrium harboring two genes PLEKHA1 and hypothetical LOC387715. The strongest association (P=10(-34)) centered over a frequent coding polymorphism, Ala69Ser, at LOC387715, strongly implicating this gene in the pathogenesis of AMD. Besides abundant expression in placenta, we demonstrate weak expression of LOC387715 in the human retina. At present, however, there is no functional information on this gene, which appears to have evolved recently within the primate lineage. The joint contribution of the common risk allele at LOC387715, Ala69Ser, and at CFH, Tyr402His, was assessed in our case-control population, which suggests an additive model indicating an independent contribution of the two gene loci to disease risk. Our data show a disease odds ratio of 57.6 (95% CI: 37.2, 89.0) conferred by homozygosity for risk alleles at both CFH and LOC387715 when compared with the baseline non-risk genotype.     

High prevalence of human papillomavirus infections in urine samples from human immunodeficiency virus-infected men

Infection with human immunodeficiency virus (HIV) and the resulting immunosuppression are associated with an increased risk for human papillomavirus (HPV) persistence and related malignancies. In the present study we investigated the prevalence of HPV in urine samples from 104 HIV-infected men with low CD4+ cell counts (<100 per mm(3)) and 115 urine samples from HIV-negative men. A high prevalence of HPV DNA (39.4%) was found in the HIV patients. Most of the HPV types were high risk (81.4%), with HPV 52 as the most prevalent type (12.5%), followed by HPV 18 (6.7%), HPV 35 (5.8%), and HPV 70 (4.8%). Multiple HPV genotypes were observed in 17 (41%) of the 41 HPV- and HIV-positive men. In contrast, only 11 (9.6%) HPV DNA-positive cases were observed among the 115 HIV-uninfected men, and 3 (27.3%) contained multiple genotypes. Quantitative analyses indicated that the HPV viral load, as measured in urine samples, is significantly higher in HIV-positive men compared to HIV-negative men. In the present study we show that urine samples are useful for detecting HPV DNA, there is a high prevalence of HPV in HIV-positive men, and the HPV viral load is substantially higher in HIV-positive than in HIV-negative men. More studies are needed to evaluate the risk and natural development of HPV-related malignancies in HIV-positive men.     

Genome-scale reconstruction of the Saccharomyces cerevisiae metabolic network

The metabolic network in the yeast Saccharomyces cerevisiae was reconstructed using currently available genomic, biochemical, and physiological information. The metabolic reactions were compartmentalized between the cytosol and the mitochondria, and transport steps between the compartments and the environment were included. A total of 708 structural open reading frames (ORFs) were accounted for in the reconstructed network, corresponding to 1035 metabolic reactions. Further, 140 reactions were included on the basis of biochemical evidence resulting in a genome-scale reconstructed metabolic network containing 1175 metabolic reactions and 584 metabolites. The number of gene functions included in the reconstructed network corresponds to approximately 16% of all characterized ORFs in S. cerevisiae. Using the reconstructed network, the metabolic capabilities of S. cerevisiae were calculated and compared with Escherichia coli. The reconstructed metabolic network is the first comprehensive network for a eukaryotic organism, and it may be used as the basis for in silico analysis of phenotypic functions.     

Increased in vivo frequency of IA-2 peptide-reactive IFNgamma+/IL-4- T cells in type 1 diabetic subjects

Active T cell recognition of islet antigens has been postulated as the pathogenic mechanism in human type 1 diabetes, but evidence is scarce. If T cells are engaged, they are expected to display increased clonal size and exhibit a T helper (Th)1/Th2 differentiation state. We used a peptide library that covers tyrosine phosphatase IA-2, a target antigen expressed in pancreatic beta cells, to probe 8 diabetic patients and 5 HLA-matched controls. When tested in a high resolution IFNgamma/IL-4 double color ELISPOT assay directly ex vivo, the number of IA-2-reactive IFNgamma producing cells was 17-fold higher in patients than in controls and IL-4 producing cells were not present. An average of 9 peptides was recognized in the patients vs. one in the controls. Determinant recognition primarily involved CD4+ cells and showed high variability among the patients. Furthermore, anti-CD28 antibody signal enhances quantitative assessment of effector T cells in T1D patients. In vitro expansion with peptides and IL-2 results in detection of responding cells in the controls and loss of disease specificity of the T cell response. Together these data provide strong evidence for the active targeting of IA-2 by Th1 memory effector cells in human type 1 diabetes.     

Expression of high- and low-affinity receptors for C3a on the human mast cell line,HMC-1

The proteolytic cleavage product of complement component 3, (C3a), like C4a and C5a, is a potent anaphylatoxin and induces the production of inflammatory mediators in phagocytes. Notably, mast cells respond to C3a with the release of vasoactive substances, including histamine. We have examined the function and receptor binding of C3a in a human leukemic mast cell line, HMC-1. Similar to chemoattractant agonists in leukocytes, C3a induced rapid cytosolic free calcium concentration increases in HMC-1 cells. EGTA did not diminish this response, indicating that mobilizable Ca²⁺ was from intracellular stores. Receptors for C3a in HMC-1 cells couple in part to Bordetella pertussis toxin-sensitive G-proteins and, therefore, appear to belong to the family of serpentine receptors that require G-proteins for signal transduction. HMC-1 cells express two types of C3a receptors, C3aR1 and C3aR2, that were shown to bind ¹²⁵I-C3a with high-(K_d1 = 2.1–4.8 nM) or low-affinity (K_d2 = 30–150 nM), and both receptors are expressed at high level: 3 × 10⁵–6 × 10⁵ C3aR1/cell and 5 × 10⁵–2.3 × 10⁶ C3aR2/cell. Results from cross-linking experiments with ¹²⁵I-C3a fully agree with the presence of two different classes of C3a receptors in HMC-1 cells. Two membrane proteins with apparent molecular masses of 54–61 kDa (p57) and 86–107 kDa (p97) could be covalently modified with ¹²⁵I-C3a, and this cross-linking was inhibited with an excess of unlabeled C3a. Many of the known agonists for leukocytes including 13 chemokines (IL-8, NAP-2, GROα, ENA-78, IP10, PF4, MCP-1, 2 and 3, RANTES, MIP-1α, MIP-1β and 1309), three neuropeptides (neuropeptide Y, somatostatin and calcitonin), as well as C5a, did not activate HMC-1 cells, indicating that C3a is one of a few protein ligands for which this cell line expresses specific receptors. The apparent selectivity for C3a and the abundant expression of C3a receptors make the HMC-1 cell line an excellent choice for the cloning of the receptor genes.