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Related Concept Videos

Thermal Strain01:19

Thermal Strain

2.8K
Thermal strain is a concept that arises when we consider how temperature changes affect structures. Unlike the conventional assumption that structures remain constant under load, real-world scenarios often involve temperature fluctuations that can significantly impact these structures. Consider a homogeneous rod with a uniform cross-section resting freely on a flat horizontal surface. If the rod's temperature increases, the rod elongates. This elongation is proportional to the temperature...
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Shearing Strain01:20

Shearing Strain

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The shearing strain represents a cubic element's angular change when subjected to shearing stress. This type of stress can transform a cube into an oblique parallelepiped without influencing normal strains. The cubic element experiences a significant transformation when exposed solely to shearing stress. Its shape alters from a perfect cube into a rhomboid, clearly demonstrating the effect of shearing strain. The degree of this strain is considered positive if it reduces the angle between the...
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Measurements of Strain01:27

Measurements of Strain

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Strain quantifies the deformation of a material under force, typically measured as normal strain, which represents the change in length when compared with the original length. Electrical strain gauges are used for enhanced accuracy. These devices consist of a conductive wire mounted on a paper backing that adheres to the material's surface. These gauges operate on the piezoresistive effect, where the wire's electrical resistance changes in response to mechanical deformation. The strain...
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Strain Energy01:13

Strain Energy

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Strain energy is a fundamental concept in the field of materials science and structural engineering, describing the energy absorbed by a material or structure when it is deformed under load.
Consider a rod that is fixed at one end and subjected to an axial force at the free end. This axial force induces stress within the rod, leading to its elongation. As the axial force increases, so does the elongation of the rod, illustrating a direct relationship between the force applied and the resulting...
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Stress-Strain Diagram01:10

Stress-Strain Diagram

2.3K
A stress-strain diagram is a crucial tool that graphically displays a material's mechanical characteristics. This diagram is derived from a tensile test performed on a carefully prepared cylindrical specimen. The specimen has two gauge marks inscribed on its central part, and the distance between these marks is known as the gauge length. The cylindrical specimen is placed in a testing machine, which applies an increasing centric load. As this load grows, so does the gauge length. This...
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Transformation of Plane Strain01:12

Transformation of Plane Strain

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When analyzing elongated structures like bars subjected to uniformly distributed loads, it is essential to understand the transformation of plane strain when coordinate axes are rotated. This transformation helps to assess how material deformation characteristics vary with orientation, which is crucial in materials science and structural engineering.
Under plane strain conditions, typical for members where one dimension significantly exceeds the others, deformations and resultant strains are...
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Related Experiment Video

Updated: Jan 21, 2026

Preparation and Use of HIV-1 Infected Primary CD4+ T-Cells as Target Cells in Natural Killer Cell Cytotoxic Assays
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Primary HIV-1 Strains Use Nef To Downmodulate HLA-E Surface Expression.

Thomas van Stigt Thans1, Janet I Akko1,2, Annika Niehrs1,2

  • 1Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.

Journal of Virology
|August 4, 2019
PubMed
Summary

Human immunodeficiency virus type 1 (HIV-1) downregulates HLA-E on infected CD4+ T cells, impacting immune evasion. This finding suggests new strategies for harnessing cellular immunity against HIV.

Keywords:
HIV-1HLA-ENef

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Area of Science:

  • Immunology
  • Virology
  • Cell Biology

Background:

  • Human immunodeficiency virus type 1 (HIV-1) evades immune detection by downregulating classical HLA class I (HLA-I) molecules.
  • HLA-E, a nonclassical HLA-I, plays a crucial role in antiviral immunity by influencing CD8+ T-cell and natural killer (NK) cell responses.
  • Previous research indicated unchanged or increased HLA-E levels on HIV-1-infected cells, contrasting with observed immune evasion mechanisms.

Purpose of the Study:

  • To investigate the surface levels of HLA-E on primary CD4+ T cells infected with different strains of HIV-1.
  • To identify the specific HIV-1 proteins responsible for modulating HLA-E surface expression.
  • To understand the implications of HLA-E downregulation for immune recognition and potential therapeutic strategies against HIV-1.

Main Methods:

  • Infection of primary CD4+ T cells with primary HIV-1 strains.
  • Analysis of surface HLA-E levels using flow cytometry.
  • Expression of HIV-1 Nef and Vpu proteins in T-cell lines.
  • Cytoplasmic tail swap experiments between HLA-A2 and HLA-E.
  • Infection with HIV-1 mutants lacking functional Nef or Vpu.

Main Results:

  • A subset of primary HIV-1 strains downregulated surface HLA-E on infected CD4+ T cells.
  • HIV-1 Nef protein was identified as a key modulator of HLA-E surface levels, targeting its cytoplasmic tail.
  • Functional Nef, and to some extent Vpu, were necessary for efficient HLA-E downmodulation.
  • Downregulation of HLA-E may reduce recognition by CD8+ T cells but increase susceptibility to NKG2A+ NK cells.

Conclusions:

  • HIV-1 actively downregulates surface HLA-E on infected primary CD4+ T cells, a novel immune evasion mechanism.
  • This downregulation impacts the balance between CD8+ T-cell and NK cell-mediated immunity.
  • Findings have significant implications for developing immunotherapies targeting HIV-1 by modulating cytotoxic cellular immunity.