Innate Immune System
- Innate immune system acts rapidly against broad threat patterns.
- Immunologic memory means a faster or stronger response after prior exposure, and the innate system lacks this feature.
- Nonspecific defense means the response does not depend on one exact antigenic target.
- Complement proteins are blood-borne proteins that help nonspecific host defense and inflammation.
- Toll-like receptors (TLRs) are innate immune receptors that recognize common pathogen patterns.
- Mast cells, eosinophils, neutrophils, macrophages, and natural killer cells are chief innate immune cells.
- Natural killer cells (NK cells) are lymphocyte-like cells that can kill virus-altered or tumor cells without thymic education.
- Complement proteins C1 through C9 participate in nonspecific host defense.
- Inflammation can be initiated by complement proteins.
- Human toll-like receptors are a family of 10 integral proteins.
- Integral proteins are proteins embedded in a membrane.
- Cell membranes and endosomal membranes contain different toll-like receptors.
- Endosomes are intracellular membrane compartments involved in sorting internalized material.
- Homodimer means a receptor pair made of two identical receptor proteins.
- Heterodimer means a receptor pair made of two different receptor proteins.
- Toll-like receptors usually form homodimers.
- Toll-like receptor 2 (TLR2) can pair with toll-like receptor 1 (TLR1) or toll-like receptor 6 (TLR6) to form heterodimers.
- Pathogen-associated molecular patterns (PAMPs) are repeating molecular patterns commonly found in pathogens.
- Toll-like receptors recognize specific pathogen-associated molecular patterns.
- Toll-like receptors 1, 2, 4, 5, 6, and 10 are cell-membrane proteins.
- Cell-membrane toll-like receptors recognize patterns from bacteria, protozoa, and fungi.
- Toll-like receptors 3, 7, 8, and 9 are endosomal-membrane proteins.
- Endosomal toll-like receptors recognize nucleic-acid patterns from viruses and some other microorganisms.
- Lipopolysaccharide is a gram-negative bacterial outer-membrane molecule recognized by toll-like receptor 4.
- Gram-negative bacteria are bacteria with a thin peptidoglycan wall and an outer membrane containing lipopolysaccharide.
- Peptidoglycan is a bacterial cell-wall polymer recognized by toll-like receptor 2.
- Gram-positive bacteria are bacteria with thick peptidoglycan cell walls.
- Toll-like receptor activation causes release of tumor necrosis factor-alpha, interleukins, and other cytokines.
- Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that promotes inflammation.
- Interleukin 1 (IL-1) and interleukin 12 (IL-12) are cytokines released after toll-like receptor activation.
- Cytokines are immune signaling proteins.
- Systemic inflammation means inflammation affecting the whole body rather than only one local area.
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