Author
Robert A. Ramos
Bio: Robert A. Ramos is an academic researcher from Rockefeller University. The author has contributed to research in topics: Tumor necrosis factor alpha & Lymphocyte antigen 96. The author has an hindex of 1, co-authored 1 publications receiving 3948 citations.
Papers
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TL;DR: CD14, a differentiation antigen of monocytes, was found to bind complexes of LPS and LBP, and blockade of CD14 with monoclonal antibodies prevented synthesis of TNF-alpha by whole blood incubated with LPS.
Abstract: Leukocytes respond to lipopolysaccharide (LPS) at nanogram per milliliter concentrations with secretion of cytokines such as tumor necrosis factor-alpha (TNF-alpha). Excess secretion of TNF-alpha causes endotoxic shock, an often fatal complication of infection. LPS in the bloodstream rapidly binds to the serum protein, lipopolysaccharide binding protein (LBP), and cellular responses to physiological levels of LPS are dependent on LBP. CD14, a differentiation antigen of monocytes, was found to bind complexes of LPS and LBP, and blockade of CD14 with monoclonal antibodies prevented synthesis of TNF-alpha by whole blood incubated with LPS. Thus, LPS may induce responses by interacting with a soluble binding protein in serum that then binds the cell surface protein CD14.
4,048 citations
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TL;DR: It is concluded that the LPS/CD14 system sets the tone of insulin sensitivity and the onset of diabetes and obesity and lowering plasma LPS concentration could be a potent strategy for the control of metabolic diseases.
Abstract: Diabetes and obesity are two metabolic diseases characterized by insulin resistance and a low-grade inflammation. Seeking an inflammatory factor causative of the onset of insulin resistance, obesity, and diabetes, we have identified bacterial lipopolysaccharide (LPS) as a triggering factor. We found that normal endotoxemia increased or decreased during the fed or fasted state, respectively, on a nutritional basis and that a 4-week high-fat diet chronically increased plasma LPS concentration two to three times, a threshold that we have defined as metabolic endotoxemia. Importantly, a high-fat diet increased the proportion of an LPS-containing microbiota in the gut. When metabolic endotoxemia was induced for 4 weeks in mice through continuous subcutaneous infusion of LPS, fasted glycemia and insulinemia and whole-body, liver, and adipose tissue weight gain were increased to a similar extent as in high-fat-fed mice. In addition, adipose tissue F4/80-positive cells and markers of inflammation, and liver triglyceride content, were increased. Furthermore, liver, but not whole-body, insulin resistance was detected in LPS-infused mice. CD14 mutant mice resisted most of the LPS and high-fat diet-induced features of metabolic diseases. This new finding demonstrates that metabolic endotoxemia dysregulates the inflammatory tone and triggers body weight gain and diabetes. We conclude that the LPS/CD14 system sets the tone of insulin sensitivity and the onset of diabetes and obesity. Lowering plasma LPS concentration could be a potent strategy for the control of metabolic diseases.
5,032 citations
TL;DR: This work has shown that activation of inflammatory and antimicrobial innate immune responses through recognition of Toll-like receptors expressed on dendritic cells triggers functional maturation of dendrites and leads to initiation of antigen-specific adaptive immune responses.
Abstract: Toll-like receptors have a crucial role in the detection of microbial infection in mammals and insects. In mammals, these receptors have evolved to recognize conserved products unique to microbial metabolism. This specificity allows the Toll proteins to detect the presence of infection and to induce activation of inflammatory and antimicrobial innate immune responses. Recognition of microbial products by Toll-like receptors expressed on dendritic cells triggers functional maturation of dendritic cells and leads to initiation of antigen-specific adaptive immune responses.
4,102 citations
TL;DR: It is demonstrated that TLR2 and TLR4 recognize different bacterial cell wall components in vivo andTLR2 plays a major role in Gram-positive bacterial recognition.
3,364 citations
TL;DR: A group of proteins that comprise the Toll or Toll-like family of receptors perform this role in vertebrate and invertebrate organisms and it is therefore not surprising that studies of the mechanism by which they act has revealed new and important insights into host defence.
Abstract: The innate immune response is the first line of defence against infectious disease. The principal challenge for the host is to detect the pathogen and mount a rapid defensive response. A group of proteins that comprise the Toll or Toll-like family of receptors perform this role in vertebrate and invertebrate organisms. This reflects a remarkable conservation of function and it is therefore not surprising that studies of the mechanism by which they act has revealed new and important insights into host defence.
3,072 citations
TL;DR: Because of the high mortality of sepsis in the face of standard treatment, many efforts have been made to improve understanding of the dysregulation of the host response in sepsi, and much has been learnt of the basic principles governing bacterial–host interactions.
Abstract: Sepsis is a condition that results from a harmful or damaging host response to infection. Many of the components of the innate immune response that are normally concerned with host defences against infection can, under some circumstances, cause cell and tissue damage and hence multiple organ failure, the clinical hallmark of sepsis. Because of the high mortality of sepsis in the face of standard treatment, many efforts have been made to improve understanding of the dysregulation of the host response in sepsis. As a result, much has been learnt of the basic principles governing bacterial-host interactions, and new opportunities for therapeutic intervention have been revealed.
2,582 citations