What is alveolar macrophage inflammation?
Alveolar macrophages are the most abundant innate immune cells in the distal lung parenchyma, located on the luminal surface of the alveolar space. They are the first to encounter incoming pathogens and pollutants and to help orchestrate the initiation and resolution of the immune response in the lung.
Where can I find alveolar macrophages in the lungs?
Oct 14, 2021 · Alveolar macrophages (AM) also known as dust cells are a type of white blood cells. The immune system is divided into the cellular and humoral components. Alveolar macrophages are the first line of defense against invading respiratory pathogens. They reside in pulmonary alveoli and the inter-alveolar septum in close proximity with pneumocytes.
What do macrophages do in the respiratory system?
Alveolar Macrophage Acute respiratory distress syndrome. Alveolar macrophages are the most common cell type normally found in BAL fluid, and... Lung Defenses: Intrinsic, Innate, and Adaptive. The alveolar macrophage plays an essential role in the killing of... Exfoliative Cytopathology. Volume 2. ...
What is the function of alveoli?
Alveolar macrophages are the primary phagocytes of the innate immune system, clearing the air spaces of infectious, toxic, or allergic particles that have evaded the mechanical defenses of the respiratory tract, such as the nasal passages, the glottis, and the mucociliary transport system.
What is the function of an alveolar macrophage quizlet?
What is the function of Alveolar Macrophages? Responsible for cleaning inhaled particles and lung surfactant.
Do alveolar macrophages secrete surfactant?
Surfactant components are recycled by type II cells or catabolized by alveolar macrophages in a highly regulated system that maintains precise levels of pulmonary surfactant throughout life. Both surfactant lipids and proteins are synthesized primarily by type II cells.
How does alveolar macrophages protect the respiratory system?
To prevent uncontrolled inflammation in the lower respiratory tract, alveolar macrophages secrete nitric oxide, prostaglandins, interleukin-4 and -10(IL-4, IL-10), and transforming growth factor-β (TGF-β).
What is the role of the alveolar macrophage and which type of Pneumocyte is this?
Surfactants are phospholipids produced by pneumocytes that prevent the collapse of alveolar walls during expiration. Another function of alveolar macrophages is to remove excess surfactant and thus maintain homeostasis.
What are alveolar macrophages? What role do they play in fibrosis?
Alveolar macrophages are the most common cell type normally found in BAL fluid, and together with interstitial macrophages play an important role in host defence and modulation of fibrosis. They are capable of releasing IL-6 and a host of mediators similar to the activated neutrophil, including TNF-α and IL-8 in response to stretch,28 and may amplify lung injury. Macrophages also release factors such as TGF-α and PDGF that stimulate fibroblast proliferation, deposition of collagen and glycosaminoglycans, angiogenesis and lung fibrosis.
What is intra alveolar macrophages?
Intra-alveolar macrophages characterized by fine vacuolation in their cytoplasm can be observed with drug toxicity (i.e., Amiodarone), chronic obstruction (“golden pneumonia”), genetic storage diseases, and the Hermansky-Pudlak syndrome (HPS). HPS is a group of autosomal recessive genetic disorders associated with Golgi apparatus abnormalities. The largest cohort of HPS (400-500 individuals) resides in northwest Puerto Rico. The phenotype is characterized clinically by oculocutaneous albinism, platelet storage pool deficiency, and variable tissue lipofuscinosis. Histopathologically, broad zones of fibrosis are seen, either pleural based or centered on the airways. Alveolar septal thickening is present and associated with prominent, clear, vacuolated type II pneumocytes (Figure 3-16 ).
What is the role of alveolar macrophages in pulmonary host defense?
Alveolar Macrophage Regulation of Inflammation. The ability of the alveolar macrophage to recruit and regulate other inflammatory cells is the major attribute allowing alveolar macrophages to locally regulate pulmonary host defenses.
What type of cell is a pneumocyte?
The type 1 pneumocyte is a flat cell with tight cell junctions that line the alveolar surface. The tight cell junctions prevent permeability of fluid into the alveolar space. The type 2 pneumocyte is a larger polygonal cell that produces surfactant and processes circulating vasoactive substances.
Do alveolar macrophages kill bacteria?
The efficiency of microbial killing by alveolar macrophages depends on the specific organism involved and the size of the initial inoculum.
What is the role of alveolar macrophages in the airspace?
Recent evidence suggests that the alveolar macrophage has an equally important role in resolving inflammation within the airspace ( 2 ). As inflammatory responses to an infectious challenge resolve, neutrophils undergo programmed cell death, or apoptosis.
What is the function of the alveolar macrophage in pneumonia?
Pneumococcal pneumonia is the prototypical respiratory infection in which these two functions of the alveolar macrophage, initiating and resolving pulmonary inflammation, are particularly important in the preservation of normal lung function.
What is the guardian of the alveolar blood interface?
Wielding the Double-Edged Sword of Inflammation. The alveolar macrophage stands as the guardian of the alveolar–blood interface, serving as the front line of cellular defense against respiratory pathogens ( 1 ). Alveolar macrophages are the primary phagocytes of the innate immune system, clearing the air spaces of infectious, toxic, ...
What are the cytokines that macrophages secrete?
When faced with larger numbers of infectious particles or more virulent microbes, alveolar macrophages synthesize and secrete a wide array of cytokines (including interleukins-1, -6, and tumor necrosis factor-α ), chemokines (including interleukin-8), and arachidonic metabolites ( 2 ).
Do alveolar macrophages recruit neutrophils?
Conceivably, the reduced numbers of alveolar macrophages in the treated mi ce may have been sufficient to initiate infla mmatory responses and recruit activated neutrophils, whereas greater numbers of alveolar macrophages are necessary to appropriately resolve inflammation.
Is interleukin-10 lower in lungs?
In addition, levels of the antiinflammatory cytokine interleukin-10 were lower in lungs of macrophage-depleted mice compared with control mice. Finally, lungs of macrophage–depleted mice showed focal areas of parenchymal destruction, which presumably was absent in control mice.
Does macrophage depletion affect inflammatory response?
Interestingly, macrophage depletion did not significantly affect the initiation of inflammatory responses against pneumococcal challenge nor the numbers of bacteria in lungs and blood within the first 48 hours after infection, in contrast to studies in experimental gram-negative pneumonia ( 5, 6 ).
What is the role of alveolar macrophages in the lung?
Alveolar macrophages are phagocytes that play a critical role in homeostasis, host defense, and tissue remodeling. Their population density is decisive for these many processes.
Why are alveolar macrophages so active?
Activity of the alveolar macrophage is relatively high, because they are located at one of the major boundaries between the body and the outside world. They are responsible for removing particles such as dust or microorganisms from the respiratory surfaces.
What cell type is the alveolar macrophage?
Such black granules may be especially common in smoker 's lungs or long-term city dwellers. The alveolar macrophage is the third cell type in the alveolus, the others are the type I and type II pneumocytes .
What is NO in macrophages?
NO is a major source of immunomodulation in rodents, and is produced by enzyme nitric oxide synthetase type 2 (NOS2) in the alveolar macrophage. NO inhibits tyrosine phosphorylation of the kinases involved in production of the interleukin-2 (IL-2) receptor, the expression of which is fundamental for T cell proliferation. In humans, however, NOS2 activity has been difficult to verify.
What are the integrins of macrophages?
Integrins are dimeric cell-surface receptors composed of alpha and beta subunits, which activates TGF-β.< TGF-β is a multifunctional cytokine that modulates a variety of biological processes such as cell growth, apoptosis, extracellular matrix synthesis, inflammation, and immune responses. TGF-β tightly regulates anti-inflammatory activity by suppressing pro-inflammatory cytokine production, thereby inhibiting T-lymphocyte function. Integrins avβ6 and avβ8 sequester latent TGF-β to the cell surface, where activation can be tightly coupled to cellular responses to environmental stress in the maintenance of homeostasis; integrins also localize activated TGFβ in the vicinity of the macrophages. Normally mature TGFβ is secreted as a latent complex with its N-terminal fragment, latency-associated peptide (LAP), which inhibits its activity. The latent complex is covalently linked to the extracellular matrix by binding to latent TGF-β-binding proteins. TGF-β is activated by diverse mechanisms in the lung, ultimately involving either proteolysis or conformational alteration of the LAP. αvβ6 integrin is able to mediate activation of TGF-β by binding to TGF-β1 LAP, which serves as a ligand binding site for the integrin, and is an essential component of the TGF-β activation apparatus. Once activated, TGFβ leads to the suppression of macrophage functionality (cytokine production and phagocytosis). Binding of activated TGF-β to its receptors expressed on alveolar macrophages induces a downstream signaling cascade, including phosphorylation of receptor-regulated Small Mothers Against Decapentaplegic (R-SMAD)homologs 2 and 3. Phosphorylated SMAD-2 and -3 then form heteromeric complexes with common-mediator SMAD 4 (co-SMAD-4). Once assembled, the complexes translocates into the nucleus via the nuclear pore with the assistance of importins alpha/beta. Once in the nucleus, these complexes accumulate and eventually act as a transcription factors, regulating the expression of TGF-β target genes. Thus TGF-β signaling involves a direct pathway from the receptors on the surface of a cell to the nucleus.
Why are phagocytes important?
They need to be selective of the material that is phagocytized to safeguard the normal cells and structures. To combat infection, the phagocytes facilitate many pattern recognition receptors (PRRs) to help recognize pathogen-associated molecular patterns (PAMPs) on the surface of pathogenic microorganisms.
Which receptors are involved in phagocytosis?
For example, phagocytosis of IgG-opsonized pathogens occurs through the Fcγ receptors (FcγR), and involves phagocyte extensions around the microbe, resulting in the production of pro-inflammatory mediators.
