antibacterial innate immune response

Definition

Target type: biologicalprocess

An defense response against a bacteria mediated through an innate immune response. An innate immune response is mediated by germline encoded components that directly recognize components of potential pathogens. [PMID:16177355, PMID:23006328]

The innate immune system serves as the first line of defense against invading pathogens, including bacteria. This system comprises various cellular and molecular components that work in concert to rapidly recognize and eliminate these threats. Here's a detailed description of the antibacterial innate immune response:

1. **Pattern Recognition:**
* **Toll-like Receptors (TLRs):** Found on the surface of immune cells, these receptors recognize specific pathogen-associated molecular patterns (PAMPs) commonly found on bacteria, such as lipopolysaccharide (LPS) from Gram-negative bacteria, peptidoglycans from both Gram-positive and Gram-negative bacteria, and flagellin from bacterial flagella.
* **NOD-like Receptors (NLRs):** These intracellular receptors sense bacterial components like peptidoglycans and muramyl dipeptide. They form inflammasomes, multiprotein complexes that activate caspase-1, a key enzyme in the production of IL-1β and IL-18.
* **RIG-I-like Receptors (RLRs):** These receptors recognize viral RNA, but they can also sense bacterial RNA, triggering the production of type I interferons (IFNs).

2. **Cellular Components:**
* **Neutrophils:** These are the most abundant white blood cells, rapidly migrating to the site of infection. They phagocytose bacteria, release antimicrobial peptides, and form neutrophil extracellular traps (NETs), which trap and kill bacteria.
* **Macrophages:** These phagocytes engulf and destroy bacteria, releasing inflammatory cytokines that recruit other immune cells. They can also present bacterial antigens to T cells, initiating adaptive immunity.
* **Dendritic Cells:** These antigen-presenting cells capture bacteria, process them, and migrate to lymph nodes, where they activate T cells, bridging the innate and adaptive immune responses.
* **Natural Killer (NK) Cells:** These lymphocytes kill infected cells that express stress-induced molecules. They release cytotoxic granules containing perforin and granzyme, which induce apoptosis in target cells.

3. **Molecular Mechanisms:**
* **Cytokine Production:** TLRs and NLRs stimulate the production of inflammatory cytokines, such as TNF-α, IL-1β, IL-6, and chemokines, which attract immune cells to the site of infection, promote inflammation, and enhance the immune response.
* **Complement System:** This cascade of proteins can directly kill bacteria by forming the membrane attack complex (MAC), which creates pores in the bacterial cell wall. It also opsonizes bacteria, making them more easily phagocytosed by immune cells.
* **Antimicrobial Peptides:** Cells release various antimicrobial peptides that disrupt bacterial cell membranes, leading to lysis. Examples include defensins, cathelicidins, and LL-37.
* **Reactive Oxygen Species (ROS):** Phagocytic cells produce ROS, such as superoxide anions and hydrogen peroxide, which damage bacterial DNA and proteins, leading to bacterial death.

4. **Inflammation:**
* Inflammation is a crucial part of the antibacterial innate immune response. It serves to contain the infection, recruit immune cells, and promote tissue repair. Signs of inflammation include redness, swelling, heat, and pain.

5. **Adaptive Immune Response:**
* The innate immune response bridges to the adaptive immune response by presenting bacterial antigens to T cells. This triggers the activation and differentiation of T cells into effector T cells that specifically target the infecting bacteria.

The antibacterial innate immune response is a complex and highly coordinated process that is crucial for protecting the host from bacterial infections. The recognition of PAMPs, activation of immune cells, and production of various effector molecules work together to eliminate the invading pathogens and prevent disease. However, dysregulation of the innate immune response can lead to chronic inflammation and autoimmune disorders.'
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Proteins (4)

Compounds (126)