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Related Concept Videos

T Cell Activation and Clonal Selection01:22

T Cell Activation and Clonal Selection

T cells are integral to our adaptive immune system, recognizing and effectively responding to foreign antigens. T cell activation and clonal selection are pivotal in orchestrating this immune response. This article elucidates these mechanisms, detailing the roles of cluster of differentiation (CD) markers, major histocompatibility complex (MHC) molecules, costimulatory signals, and the process of clonal selection.
Naive T cells that have not yet encountered an antigen express two primary CD...
Receptor Downregulation in MVBs01:15

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Multivesicular bodies (MVBs) are mature endosomes that sort ubiquitinated proteins and then fuse with lysosomes to degrade the sorted proteins. Epidermal growth factor (EGF) and its receptor (EGFR) form a complex that can be internalized through endocytosis, sorted into an MVB, and later degraded.
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T Cell Types and Functions01:24

T Cell Types and Functions

When T cells with CD4 markers are activated, they give rise to two types of effector cells: helper T cells and regulatory T cells. Meanwhile, T cells with CD8 markers differentiate into effector cytotoxic T cells. The differentiation of CD4 T cells into helper T cell subsets, such as Th1, Th2, and Th17 cells, is dependent on the antigen type, antigen-presenting cell, and regulatory cytokines.
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B Cell Activation and Differentiation01:24

B Cell Activation and Differentiation

The adaptive immune response, a sophisticated defense mechanism, relies on the activation and differentiation of B lymphocytes, or B cells. These processes enable our bodies to mount a tailored response against specific pathogens such as bacteria, free virus particles, toxins, and parasites.
When naive B cells encounter a specific antigen that can bind to the B cell receptor (BCR) on their surface, they undergo sensitization to respond to the antigen's presence. Sensitization begins with...

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An Endothelial Planar Cell Model for Imaging Immunological Synapse Dynamics
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Semaphorin 7A protein variants differentially regulate T-cell activity.

Christiane Gras1, Britta Eiz-Vesper, Axel Seltsam

  • 1Institute for Transfusion Medicine, Hannover Medical School, Hannover, Germany.

Transfusion
|August 1, 2012
PubMed
Summary
This summary is machine-generated.

A Semaphorin 7A (Sema7A) variant, R461C, activates T-cells independently of antigens, unlike wild-type Sema7A. This Sema7A R461C variant promotes T-cell proliferation and cytotoxic responses, suggesting a role in immune regulation.

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Area of Science:

  • Immunology
  • Molecular Biology
  • Genetics

Background:

  • Semaphorin 7A (Sema7A) is a molecule with immunomodulatory functions and is associated with the John-Milton-Hagen blood group antigen.
  • The precise regulatory effects of Sema7A on T-cell activation remain incompletely understood.
  • This study investigates the functional impact of a specific Sema7A polymorphism, R461C, on T-cell responses.

Purpose of the Study:

  • To investigate the functional role of the R461C Sema7A polymorphism on T-cell activation and responses.
  • To compare the effects of wild-type Sema7A (Sema7A_wt) and the R461C variant (Sema7A_R461C) on T-cell behavior.

Main Methods:

  • Production of soluble recombinant wild-type Sema7A (Sema7A_wt) and Sema7A_R461C.
  • Assays to assess T-cell proliferation, phenotypic changes, granzyme B transcript levels, and cytokine secretion.
  • Antibody blocking studies to identify mediating pathways, specifically β1 integrin dependence.

Main Results:

  • Sema7A_wt did not influence T-cell activity.
  • Sema7A_R461C induced significant antigen-independent T-cell activation, including proliferation and a cytotoxic phenotype in CD4+ T-cells.
  • Sema7A_R461C demonstrated a strong costimulatory effect on T-cell responses during antigen stimulation, upregulating granzyme B transcripts significantly.
  • T-cell activation mediated by Sema7A_R461C was largely dependent on β1 integrin.

Conclusions:

  • The Sema7A R461C variant differentially regulates T-cell responses compared to wild-type Sema7A.
  • Given Sema7A's role in inflammation, Sema7A_R461C may be implicated in autoimmune diseases and other disorders.
  • Further research is necessary to fully elucidate the regulatory functions of Sema7A and its variants in immune responses.