Apolipoprotein-mediated pathways of lipid antigen presentation

Peptide antigens are presented to T cells by major histocompatibility complex (MHC) molecules, with endogenous peptides presented by MHC class I and exogenous peptides presented by MHC class II. In contrast to the MHC system, CD1 molecules bind lipid antigens that are presented at the antigen-presenting cell (APC) surface to lipid antigen-reactive T cells. Because CD1 molecules survey endocytic compartments, it is self-evident that they encounter antigens from extracellular sources. However, the mechanisms of exogenous lipid antigen delivery to CD1-antigen-loading compartments are not known. Serum apolipoproteins are mediators of extracellular lipid transport for metabolic needs. Here we define the pathways mediating markedly efficient exogenous lipid antigen delivery by apolipoproteins to achieve T-cell activation. Apolipoprotein E binds lipid antigens and delivers them by receptor-mediated uptake into endosomal compartments containing CD1 in APCs. Apolipoprotein E mediates the presentation of serum-borne lipid antigens and can be secreted by APCs as a mechanism to survey the local environment to capture antigens or to transfer microbial lipids from infected cells to bystander APCs. Thus, the immune system has co-opted a component of lipid metabolism to develop immunological responses to lipid antigens.     

Zur reproduzierbarkeit der Rf in der Dünnschicht-Chromatographie

Summary Conditions are discussed which influence Rf¹ on thinlayer chromatograms, and directions are given to guarantee good reproducibility. Variance of Rf on thinlayer chromatograms is of the same order of magnitude as on paper chromatograms.

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Der Ausdruck Rf-Wert ist bei häufiger Wiederholung umständlich. Wir gebrauchen an seiner Stelle: das Rf (Singular), die Rf (Plural).

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Die Mittel zur Durchführung dieser Arbeit verdanken wir Arbeitsbeschaffungskrediten des Bundes (M.B.) sowie einer Studienbeihilfe vom Land Baden-Württemberg (A.N.).     

Dünnschicht-Chromatographie von Aminosäuren

Summary Amino acid separation with 6 different solvents on chromatoplates prepared from Kieselgel G (Merck) is described. As demonstrated in Figur 8 and discussed in the text, this technique is equal or superior to paper chromatography.     

A functional T3 molecule associated with a novel heterodimer on the surface of immature human thymocytes

The known T-cell receptors (TCRs) involved in the recognition of antigen and major histocompatibility complex (MHC) molecules are glycoproteins comprised of polymorphic disulphide-linked alpha- and beta-chains. The genes encoding these chains are homologous to immunoglobulin genes and consist of V (variable), J (joining) and C (constant) regions that rearrange during development. TCRs are expressed relatively late in thymocyte development and only in association with an invariant molecular complex of proteins termed T3. Immature thymocytes do not express the TCR-T3 complex but do express messenger RNA encoding a third rearranging T-cell receptor-like gene, termed T gamma. Here we report a clone of normal immature T4-T8- human thymocytes, designated CII, which does not express mature mRNA for T alpha or T beta genes, but does express high levels of T gamma mRNA. This clone also expresses high levels of surface T3, and antibodies to T3 induce immunologically relevant functions in CII cells. Immunoprecipitation of CII surface-labelled proteins with anti-T3 co-precipitates a T3 molecular complex together with two additional and novel peptides of relative molecular mass (Mr), 44,000 (44K) and 62,000 (62K).     

Two-level additive Schwarz preconditioners for plate elements

We present a theory of two-level additive Schwarz preconditioners for plate elements. It is applicable to the cases where the finite element spaces on the two levels are (I) conforming and nested, (II) conforming and nonnested, and (III) nonconforming and nonnested. The condition number of the preconditioned system is independent of the mesh sizes and the number of subdomains in the case of generous overlap.     

The role of long range forces in ordered arrays of tobacco mosaic virus.

We examine the role of electrostatic repulsion and van der Waals' attraction in determining interviral spacings in 'equilibrium' gels of tobacco mosaic virus. The observed spacings are inconsistent with a force-balance model. Experimental probes of the role of forces are suggested.     

Intracellular response byTetrahymena pyriformis to Fluids from Unimmunized animals

Résumé Dans leTetrahymena pyriformis, les sérums des lapins et humains et les ascites fluides des souris ont une apparence bipolaire. Les petit «corps» s'accumulent antérieurement, les grands «corps» postérieurement. On peut présumer que la réduction de la tension du O₂ et/ou l'augmentation de la tension du CO₂ sont requis, puisque l'état bipolaire ne s'est produit que dans des conditions limitées d'exposition à l'air. La bipolarisation est reversible. Les animaux bipolaires qui ont été exposés brièvement à l'air ressemblent aux animaux normaux.