Flashcards in Defenses and Deficiencies Part 3 Deck (18):
What are mast cells?
They are resident cells found in lamina propria and submucosa; They do not phagocytose, however they secrete granules which stimulate an inflammatory response.
What can activate a mast cell?
C3a, C4a, C5a, DAMPs, PAMPs, substance P (released by nociceptors), Opiates, and allergens.
How do you know a mast cell has been activated?
It has degranulated.
What are the steps to mast cell granulation?
Once a mast cell is exposed to the antigen at least twice.
1. Antibody (IgE) binds to mast cell.
2. After second exposure, the antigen binds to the antibody.
3. Mast cell degranulates.
What are in the granules of mast cells?
Histamines, Serotonin, Heparin, proteoglycans, neutral proteases.
What does histamine do?
Causes LOCAL vasodilation by activating nitric oxide in endothelial cells; Relaxes smooth muscle and prevents platelets from attaching to endothelium. Smooth muscle contractant and neutrophil chemoattractant.
What does Serotonin do?
Causes local vasodilation, stimulates nocioreceptors
What does heparin do?
Temporarily prevents fibrin from forming; Thrombin is inactivated.
What do neutral proteases do?
Cleaves C3 into C3a which stimulates more degranulation. Cleaves fibronectin and type 4 collagen; Degrades basal lamina of capillary beds. This increases capillary permeability, attracts fibroblasts and activates clotting.
What else is produced by mast cells?
Prostaglandins and Leukotrienes; Prolongs effects that were initiated by histamine and serotonin, also are chemoattractants for leukocytes.
What cytokines are secreted by mast cells?
TNF-a, IL-1, Chemokines, Interleukin-4
What are the functions of the macrophage?
Phagocytosis, Secretion of cytokines and chemokines, Present to T cells, and manage wound repair by stimulating angiogenesis and fibrosis.
The cytokines and chemokines produced by macrophages do what?
1. Stimulate innate inflammatory responses.
2. Stimulate NK cell activity.
3. Modify B and T lymphocyte activity.
The binding of cytokines to macrophages do what?
Kill the microbe
When the complement bound to the bacteria is also bound to the macrophage, what happens?
Kill the microbe
When the microbe is bound to the toll-like receptor, what does the macrophage do?
Secrets cytokines; Causes inflammation, and enhances adaptive immunity.
Which enzymes are activated by the combination of the phagosome and lysosome?
1. Phagocyte oxidase: Generates ROS, H202, O2- and respiratory burst.
2. Nitric oxide synthetase: Generates nitric oxide which combines with superoxide to produce peroxynitrite.