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Questions and Answers
What is the consequence of macrophages expressing diphtheria toxin receptor (CD96+ cells)?
What is the consequence of macrophages expressing diphtheria toxin receptor (CD96+ cells)?
What triggers the activation of innate immune cells following localized tissue damage?
What triggers the activation of innate immune cells following localized tissue damage?
What role do cytokines play in the inflammatory response?
What role do cytokines play in the inflammatory response?
During diapedesis, what happens to the endothelial junctions?
During diapedesis, what happens to the endothelial junctions?
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What is a primary effect of mast cell activation during an inflammatory response?
What is a primary effect of mast cell activation during an inflammatory response?
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Which cell type is considered the first responder during an immune response to infection?
Which cell type is considered the first responder during an immune response to infection?
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What is the effect of cytokines like TNF and IL-1 on endothelial cells?
What is the effect of cytokines like TNF and IL-1 on endothelial cells?
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What keeps resident macrophages in tissues during the inflammatory response?
What keeps resident macrophages in tissues during the inflammatory response?
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Study Notes
Tattoo Ink and Immune Response
- Macrophages in the skin engulf tattoo ink particles.
- Not all ink is phagocytized because macrophages carrying ink are destroyed and new macrophages engulf the remaining ink, continuing a cycle.
- This cycle is possible because macrophages express the diphtheria toxin receptor (CD96+ cells).
- Unlike infection, the immune system does not respond to the ink because there are no DAMPs or microbial patterns to trigger the immune response.
- Cytokine response is low, and phagocytosis enzymes are not active.
- Resident macrophages do not migrate.
Inflammation
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Before Injury:
- Monocytes and macrophages circulate in the bloodstream.
- Resident macrophages and dendritic cells are present in tissues.
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When Injured:
- Damaged tissue signals the immune response.
- Bacteria may enter the tissue.
- Innate immune cells are activated.
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Immune response to injury:
- New macrophages migrate to the injured area.
- They engulf invaders and damaged cells, causing tissue repair.
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Inflammatory Response to Injury:
- Damaged cells release neutrophils and cytokines.
- These cells release chemical mediators (cytokines/chemokines, histamine, bioactive lipids such as IFN, IL-6, IL-1, histamine)
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Effects on Capillaries:
- Mast cells and histamine are released, causing vasodilation in capillaries and venules.
- Increased permeability allows fluid to leak from the capillaries into the tissues causing edema (swelling) and redness.
- Blood volume flow slows causing heat.
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Extravasation (White Blood Cell Migration):
- Rolling: Selectins on the surface of endothelial cells (blood vessel lining) bind to sugar molecules on neutrophils, initiating an attachment and rolling motion.
- Activation: Cytokines like TNF and IL-1 cause endothelial cells to express ICAMs (intercellular adhesion molecules). Chemokines cause WBC to express high-affinity integrins. This results in strong binding of the WBC to the endothelial cells.
- Arrest: Leukocytes adhere strongly to endothelial cells and spread, causing them to migrate into the tissue.
- Diapedesis: Endothelial junctions open and allow passage of leukocytes into the tissue through a process called diapedesis. The presence of neutrophils in the tissue indicates an infection.
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Immune Response to Infection:
- Neutrophils are the first responders during infection.
- Monocytes and macrophages also provide protection.
- Dendritic cells and macrophages transport antigens to the lymph nodes to activate the adaptive immune response.
Immune Cells
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Dendritic Cells:
- They are present in tissues and are responsible for recognizing danger signals and releasing cytokines.
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Mast Cells:
- They are located in the skin and mucosal tissues, responding to injury by releasing histamine.
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Description
Explore how tattoo ink interacts with the immune system, particularly the role of macrophages in engulfing ink particles. This quiz discusses the unique immune response to tattoo ink compared to infections and the inflammatory process following skin injuries.
