Naturally Occurring Antibodies (aka natural antibodies or NAbs) are produced by some B cell subsets and are present in the bloodstream without prior exposure to specific pathogens. They provide immediate, non-specific defense against a wide range of microorganisms. NAbs can recognize and bind to common structural features shared by many pathogens, facilitating their neutralization and clearance.
Pentraxins are a family of proteins involved in the humoral innate immune response. Examples include C-reactive protein (CRP) and serum amyloid P (SAP). Pentraxins can recognize and bind to various pathogens and damaged cells. Their activation triggers immune responses, such as opsonization, which enhances the phagocytosis of pathogens by phagocytic cells like macrophages.
The complement system is a complex series of proteins that enhance the immune response by acting as effectors for several innate immune mechanisms:
- Complement activation leads to the formation of membrane attack complexes (MACs), which can directly lyse pathogens.
- Additionally, complement proteins opsonize pathogens, marking them for phagocytosis.
- Complement activation also promotes inflammation and attracts immune cells to the site of infection.
The contact system (aka contact cascade or kinin-kallikrein system) is part of the innate immune response. It involves a series of enzymatic reactions leading to the generation of bradykinin, a peptide that induces vasodilation and increased vascular permeability. This process enhances the recruitment of immune cells and promotes the clearance of pathogens from the affected tissue.
Next Topic: The Cell-Mediated Innate Immune System
Source: ChatGPT response prompted and edited by Joel Graff.
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