Analysis of the CD1 Antigen Presenting System in Humanized SCID Mice

CD1 molecules are glycoproteins that present lipids and glycolipids for recognition by T cells. CD1-dependent immune activation has been implicated in a wide range of immune responses, however, our understanding of the role of this pathway in human disease remains limited because of species differences between humans and other mammals: whereas humans express five different CD1 gene products (CD1a, CD1b, CD1c, CD1d, and CD1e), muroid rodents express only one CD1 isoform (CD1d). Here we report that immune deficient mice engrafted with human fetal thymus, liver, and CD34+ hematopoietic stem cells develop a functional human CD1 compartment. CD1a, b, c, and d isoforms were highly expressed by human thymocytes, and CD1a+ cells with a dendritic morphology were present in the thymic medulla. CD1+ cells were also detected in spleen, liver, and lungs. APCs from spleen and liver were capable of presenting bacterial glycolipids to human CD1-restricted T cells. ELISpot analyses of splenocytes demonstrated the presence of CD1-reactive IFN-γ producing cells. CD1d tetramer staining directly identified human iNKT cells in spleen and liver samples from engrafted mice, and injection of the glycolipid antigen α-GalCer resulted in rapid elevation of human IFN-γ and IL-4 levels in the blood indicating that the human iNKT cells are biologically active in vivo. Together, these results demonstrate that the human CD1 system is present and functionally competent in this humanized mouse model. Thus, this system provides a new opportunity to study the role of CD1-related immune activation in infections to human-specific pathogens

Intergenic regions of Borrelia plasmids contain phylogenetically conserved RNA secondary structure motifs

<p>Abstract</p> <p>Background</p> <p><it>Borrelia </it>species are unusual in that they contain a large number of linear and circular plasmids. Many of these plasmids have long intergenic regions. These regions have many fragmented genes, repeated sequences and appear to be in a state of flux, but they may serve as reservoirs for evolutionary change and/or maintain stable motifs such as small RNA genes.</p> <p>Results</p> <p>In an in silico study, intergenic regions of <it>Borrelia </it>plasmids were scanned for phylogenetically conserved stem loop structures that may represent functional units at the RNA level. Five repeat sequences were found that could fold into stable RNA-type stem loop structures, three of which are closely linked to protein genes, one of which is a member of the <it>Borrelia </it>lipoprotein_1 super family genes and another is the complement regulator-acquiring surface protein_1 (CRASP-1) family. Modeled secondary structures of repeat sequences display numerous base-pair compensatory changes in stem regions, including C-G→A-U transversions when orthologous sequences are compared. Base-pair compensatory changes constitute strong evidence for phylogenetic conservation of secondary structure.</p> <p>Conclusion</p> <p>Intergenic regions of <it>Borrelia </it>species carry evolutionarily stable RNA secondary structure motifs. Of major interest is that some motifs are associated with protein genes that show large sequence variability. The cell may conserve these RNA motifs whereas allow a large flux in amino acid sequence, possibly to create new virulence factors but with associated RNA motifs intact.</p

New Experimental Limits on Macroscopic Forces Below 100 Microns

Results of an experimental search for new macroscopic forces with Yukawa range between 5 and 500 microns are presented. The experiment uses 1 kHz mechanical oscillators as test masses with a stiff conducting shield between them to suppress backgrounds. No signal is observed above the instrumental thermal noise after 22 hours of integration time. These results provide the strongest limits to date between 10 and 100 microns, improve on previous limits by as much as three orders of magnitude, and rule out half of the remaining parameter space for predictions of string-inspired models with low-energy supersymmetry breaking. New forces of four times gravitational strength or greater are excluded at the 95% confidence level for interaction ranges between 200 and 500 microns.Comment: 25 Pages, 7 Figures: Minor Correction

Challenges and strategies of children and adolescents with inflammatory bowel disease: a qualitative examination

© 2007 Nicholas et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

A Macrophage Response to Mycobacterium leprae Phenolic Glycolipid Initiates Nerve Damage in Leprosy

$\textit{Mycobacterium leprae}$ causes leprosy and is unique among mycobacterial diseases in producing peripheral neuropathy. This debilitating morbidity is attributed to axon demyelination resulting from direct interaction of the $\textit{M. leprae}$-specific phenolic glycolipid 1 (PGL-1) with myelinating glia and their subsequent infection. Here, we use transparent zebrafish larvae to visualize the earliest events of $\textit{M. leprae}$-induced nerve damage. We find that demyelination and axonal damage are not directly initiated by $\textit{M. leprae}$ but by infected macrophages that patrol axons; demyelination occurs in areas of intimate contact. PGL-1 confers this neurotoxic response on macrophages: macrophages infected with $\textit{M. marinum}$-expressing PGL-1 also damage axons. PGL-1 induces nitric oxide synthase in infected macrophages, and the resultant increase in reactive nitrogen species damages axons by injuring their mitochondria and inducing demyelination. Our findings implicate the response of innate macrophages to $\textit{M. leprae}$ PGL-1 in initiating nerve damage in leprosy.This work was supported by an A.P. Giannini Foundation Postdoctoral Fellowship, an NIH training grant (T32 AI1007411), and an NIH NRSA Postdoctoral Fellowship (AI104240) to C.A.M.; an NSF Predoctoral Fellowship and NIH training grant T32 AI55396 to C.J.C.; a UCLA Clinical Translational Science Institute grant (UL1TR001881 to K.K.S.); K08AR066545 to P.O.S.; U19AI111224 and R01AI049313 to D.B.M.; an NIH grant (R01AR064582) to A.S.; the NIH Director’s Pioneer Award, an NIH MERIT award (R37AI054503), and a Wellcome Trust Principal Research Fellowship to L.R

Natural Killer T Cells Activated by a Lipopeptidophosphoglycan from Entamoeba histolytica Are Critically Important To Control Amebic Liver Abscess

The innate immune response is supposed to play an essential role in the control of amebic liver abscess (ALA), a severe form of invasive amoebiasis due to infection with the protozoan parasite Entamoeba histolytica. In a mouse model for the disease, we previously demonstrated that Jα18-/- mice, lacking invariant natural killer T (iNKT) cells, suffer from more severe abscess development. Here we show that the specific activation of iNKT cells using α-galactosylceramide (α-GalCer) induces a significant reduction in the sizes of ALA lesions, whereas CD1d−/− mice develop more severe abscesses. We identified a lipopeptidophosphoglycan from E. histolytica membranes (EhLPPG) as a possible natural NKT cell ligand and show that the purified phosphoinositol (PI) moiety of this molecule induces protective IFN-γ but not IL-4 production in NKT cells. The main component of EhLPPG responsible for NKT cell activation is a diacylated PI, (1-O-[(28∶0)-lyso-glycero-3-phosphatidyl-]2-O-(C16:0)-Ins). IFN-γ production by NKT cells requires the presence of CD1d and simultaneously TLR receptor signalling through MyD88 and secretion of IL-12. Similar to α-GalCer application, EhLPPG treatment significantly reduces the severity of ALA in ameba-infected mice. Our results suggest that EhLPPG is an amebic molecule that is important for the limitation of ALA development and may explain why the majority of E. histolytica-infected individuals do not develop amebic liver abscess

Increase in mammography detected breast cancer over time at a community based regional cancer center: a longitudinal cohort study 1990–2005

Background: Coincident with the advent of mammography screening, breast carcinoma in situ has increased in the US population. Methods: We conducted a prospective cohort study of all women presenting with primary breast cancer, aged 21-94, and biopsy confirmed Stage 0-IV from 1990-2005 identified and tracked by our registry. Clinical presentation characteristics including age, race, TNM stage, family and pregnancy history, histologic type and method of detection by patient (PtD), physician (PhysD) or mammography (MgD) were chart abstracted at time of diagnosis. Cases with unknown or other method of detection (n = 84), or unusual cell types (n = 26) were removed (n = 6074). Results: From 1990 to 1998 the percentage of PtD and MgD cases was roughly equivalent. In 1999 the percentage of MgD cases increased to 56% and PtD dropped to 37%, a significant 20% differential, constant to 2005 (Pearson chi square = 120.99, p less than .001). Overall, percent TNM stage 0 (breast carcinoma in situ) cases increased after 1990, percent stage I and III cases declined, and stage II and IV cases remained constant (Pearson chi square = 218.36, p less than .001). Increase in MgD over time differed by age group with an 8.5% increase among women age 40-49 and 12% increase among women age 50-95. Women age 21-39 rarely had MgD BC. In forward stepwise logistic regression modeling, significant predictors of MgD BC by order of entry were TNM stage, age at diagnosis, diagnosis year, and race (chi square = 1867.56, p less than .001). Conclusion: In our cohort the relative proportion of mammography detected breast cancer increased over time with a higher increase among women age 50+ and an increase of breast carcinoma in situ exclusively among MgD cases. The increase among women currently targeted by mammography screening programs (age = 50) combined with an increase of breast carcinoma in situ most often detected by mammography screening indicates a possible incidence shift to lower stage breast cancer as a result of mammographic detection.Kaplan Research Fun

Mrp1 is involved in lipid presentation and iNKT cell activation by Streptococcus pneumoniae

The CD1d pathway present lipid antigens resulting in the activation of iNKT cells but the complete pathway remains to be fully elucidated. Here, Chandra et al. use an siRNA screen and identify Mrp1 as crucial for CD1d lipid presentation and activation of iNKT in the context of Streptococcus pneumoniae infection

Endosomal MR1 Trafficking Plays a Key Role in Presentation of Mycobacterium tuberculosis Ligands to MAIT Cells

Mucosal-Associated Invariant T (MAIT) cells, present in high frequency in airway and other mucosal tissues, have Th1 effector capacity positioning them to play a critical role in the early immune response to intracellular pathogens, including Mycobacterium tuberculosis (Mtb). MR1 is a highly conserved Class I-like molecule that presents vitamin B metabolites to MAIT cells. The mechanisms for loading these ubiquitous small molecules are likely to be tightly regulated to prevent inappropriate MAIT cell activation. To define the intracellular localization of MR1, we analyzed the distribution of an MR1-GFP fusion protein in antigen presenting cells. We found that MR1 localized to endosomes and was translocated to the cell surface upon addition of 6-formyl pterin (6-FP). To understand the mechanisms by which MR1 antigens are presented, we used a lentiviral shRNA screen to identify trafficking molecules that are required for the presentation of Mtb antigen to HLA-diverse T cells. We identified Stx18, VAMP4, and Rab6 as trafficking molecules regulating MR1-dependent MAIT cell recognition of Mtb-infected cells. Stx18 but not VAMP4 or Rab6 knockdown also resulted in decreased 6-FP-dependent surface translocation of MR1 suggesting distinct pathways for loading of exogenous ligands and intracellular mycobacterially-derived ligands. We postulate that endosome-mediated trafficking of MR1 allows for selective sampling of the intracellular environment.Career Development Award: (#IK2 CX000538); U.S. Department of Veterans Affairs Clinical Sciences Research and Development Program (MJH); U.S.Department of Veterans Affairs Biomedical Laboratory Research and Development Program (DML) Merit Award: (#I01 BX000533); American Lung Association: (RT-350058)