response to Gram-negative bacterium

Definition

Target type: biologicalprocess

Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus from a Gram-negative bacterium. [PMID:23664307]

The response to Gram-negative bacteria is a complex and multi-faceted process involving a coordinated effort by the host's immune system to recognize, neutralize, and eliminate these pathogens. This process is initiated when the host encounters Gram-negative bacteria, which possess unique structural features that trigger specific immune responses.

The first step involves the recognition of Gram-negative bacteria by the host's innate immune system. This recognition is mediated by pattern recognition receptors (PRRs), which are expressed on various immune cells such as macrophages, neutrophils, and dendritic cells. PRRs recognize pathogen-associated molecular patterns (PAMPs) that are specifically associated with Gram-negative bacteria. These PAMPs include lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, flagellin, the protein subunit of bacterial flagella, and peptidoglycan, a component of the bacterial cell wall.

Upon recognition of PAMPs by PRRs, a cascade of signaling events is initiated, leading to the activation of various transcription factors, including NF-κB and AP-1. These transcription factors induce the expression of a wide range of pro-inflammatory cytokines and chemokines, such as TNF-α, IL-1β, IL-6, and CXCL8. These inflammatory mediators play a crucial role in recruiting immune cells to the site of infection, promoting the elimination of bacteria, and initiating tissue repair.

The recruitment of immune cells to the site of infection is essential for controlling bacterial proliferation. Neutrophils, which are the first responders to bacterial infection, are attracted by chemokines and engulf and kill bacteria through phagocytosis. Macrophages, which arrive later, also phagocytose bacteria and release additional inflammatory mediators to enhance the immune response. Dendritic cells, specialized antigen-presenting cells, capture bacterial antigens and migrate to lymph nodes, where they present these antigens to T cells.

T cells, which are a key component of the adaptive immune response, are activated by antigen-presenting cells and differentiate into various effector T cell subsets, including cytotoxic T lymphocytes (CTLs) and T helper cells. CTLs directly kill bacteria-infected cells, while T helper cells provide support to other immune cells. For example, T helper 1 (Th1) cells produce cytokines such as IFN-γ, which activate macrophages and promote bacterial killing.

The adaptive immune response also involves the generation of antibodies, which are proteins that specifically bind to bacterial antigens. Antibodies can neutralize bacteria by blocking their attachment to host cells, promote phagocytosis by immune cells, and activate complement, a system of proteins that can directly kill bacteria.

The response to Gram-negative bacteria is highly complex and involves a delicate balance between the host's immune system and the bacterial pathogen. An excessive inflammatory response can lead to tissue damage and disease, while an insufficient response can allow bacterial proliferation and systemic infection. Therefore, a well-coordinated and regulated immune response is crucial for effectively controlling Gram-negative bacterial infections.'
"

Proteins (1)

Compounds (18)