RAPID COMMUNICATION: TLR4 expressed but with reduced functionality on equine B lymphocytes.
Abstract: Varying susceptibility exists among mammalian species to the development of potentially fatal endotoxemia due to gram-negative bacteria molecular component, lipopolysaccharide (LPS). Toll-like receptor 4 (TLR4) is responsible for LPS-associated immune response and is expressed on numerous immune cells including B lymphocytes. TLR4 is expressed in a functional form on mouse B lymphocytes, a species much less susceptible to endotoxemia compared with humans who are highly sensitive to endotoxin. Humans possess B lymphocytes that are not responsive to LPS. Likewise, horses are highly susceptible to endotoxemia but the expression and function of TLR4 on horse B lymphocytes is not known. Colic, the major cause of mortality in horses, is often complicated by resultant endotoxemia. The objective of this study was to determine the expression and function of TLR4 on equine B lymphocytes. Lymphocytes were isolated from peripheral blood mononuclear cells that were collected from six horses, and the expression and function of TLR4 was analyzed for each horse. Flow cytometry results indicate TLR4 is expressed on horse B lymphocytes but stimulation with LPS did not alter this expression (P = 0.99) compared with unstimulated B lymphocytes after 24 h. After 72 h of in vitro LPS stimulation, analysis of cell proliferation dye by flow cytometry demonstrated that equine B lymphocytes did not proliferate, while mouse B lymphocytes predictably did. Furthermore, the total number of LPS stimulated equine B lymphocytes did not significantly differ from unstimulated cells after 72 h of culture (P = 0.92). Horse lymphocytes exhibited no significant differences in the measured TLR4 signaling pathway genes (TLR4, IL-10, IL-6, IFNβ, and TNFα) when expression was compared with LPS stimulated vs. unstimulated cells. In conclusion, while TLR4 is expressed on horse B lymphocytes, it appears minimally responsive to LPS in vitro, similar to results seen in human B lymphocytes. While further studies are still needed, our work reveals a potential link between B lymphocyte TLR4 expression and endotoxin sensitivity.
© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Publication Date: 2019-03-23 PubMed ID: 30901382PubMed Central: PMC6488325DOI: 10.1093/jas/skz074Google Scholar: Lookup
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- Journal Article
Summary
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The research examines the expression and function of Toll-like receptor 4 (TLR4) on B lymphocytes in horses. It concludes that while TLR4 is found on these immune cells, they seemingly do not respond robustly to exposure with lipopolysaccharide (LPS), a molecule often associated with severe bacterial infections and endotoxemia.
Context and Objective
- The study seeks to understand the varying susceptibility of mammals to endotoxemia, a potentially fatal condition triggered by LPS, a molecular component of gram-negative bacteria.
- This response is largely controlled by TLR4, a protein found in many immune cells (including B lymphocytes) that plays a crucial role in the body’s immune response.
- Scientists wanted to determine if horses, which are known to be highly susceptible to endotoxemia, have functional TLR4 on their B lymphocytes. The relevance of this study is heightened by the fact that colic, a common cause of horse mortality, can be complicated by endotoxemia.
Method and Findings
- The team isolated lymphocytes from the blood of six horses and conducted a detailed analysis of TLR4 expression and functionality.
- Results from flow cytometry confirmed that TLR4 was expressed on B lymphocytes in horses, but LPS did not modify this expression.
- In vitro tests showed that after 72 hours of stimulation with LPS, horse B lymphocytes did not proliferate, contradicting behavior observed in mice. The total number of LPS stimulated horse B lymphocytes did not significantly differ from unstimulated cells after this 72-hour period.
- No major differences were found in the expression of TLR4 signaling pathway genes (such as TLR4, IL-10, IL-6, IFNβ, and TNFα) when comparing LPS stimulated versus unstimulated cells.
Conclusion and Implications
- The researchers concluded that although TLR4 is present on horse B lymphocytes, these cells do not extensively respond to LPS in vitro. This finding aligns with comparable observations made in human B lymphocytes.
- This study suggests a potential association between B lymphocyte TLR4 expression and sensitivity to endotoxins; however, additional research is necessary. Understanding the molecular mechanics of this susceptibility may eventually help in the development of effective treatments for endotoxemia in susceptible species.
Cite This Article
APA
Hay AN, Potter A, Kasmark L, Zhu J, Leeth CM.
(2019).
RAPID COMMUNICATION: TLR4 expressed but with reduced functionality on equine B lymphocytes.
J Anim Sci, 97(5), 2175-2180.
https://doi.org/10.1093/jas/skz074 Publication
Researcher Affiliations
- Virginia Tech University, Animal and Poultry Science Department, Blacksburg, VA.
- Virginia Tech University, Animal and Poultry Science Department, Blacksburg, VA.
- Virginia Tech University, Animal and Poultry Science Department, Blacksburg, VA.
- Virginia Tech University, Animal and Poultry Science Department, Blacksburg, VA.
- Virginia Tech University, Animal and Poultry Science Department, Blacksburg, VA.
MeSH Terms
- Animals
- B-Lymphocytes / immunology
- Cytokines / analysis
- Endotoxemia / immunology
- Endotoxemia / veterinary
- Flow Cytometry / veterinary
- Horse Diseases / immunology
- Horses
- Humans
- Leukocytes / immunology
- Leukocytes, Mononuclear / immunology
- Lipopolysaccharides / administration & dosage
- Lymphocytes / immunology
- Male
- Mice
- Mice, Inbred C57BL
- Signal Transduction
- Toll-Like Receptor 4 / genetics
- Toll-Like Receptor 4 / metabolism
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Citations
This article has been cited 1 times.- Yamasaki A, Okazaki R, Harada T. Neutrophils and Asthma. Diagnostics (Basel) 2022 May 8;12(5).
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