Immunology Course 2023
14 Dec 2023
Day 4 · Macrophages and Dendritic Cells
Session 1: Prof Siddharth Jhunjunwala, Department of Bioengineering, IISc
Blood Cells
- Cellular Components:
- RBC: Carry hemoglobin
- WBC
- Platelets
- Non-Cellular Components:
- Proteins
- Water
- Lipids, Sugars
- Motion of Heart:
- Discontinuous pump → Continuous blood flow
- Blood is a non-Newtonian fluid, flowing close to laminar.
- Non-cellular fluids flow at the periphery in laminar flow.
- Interaction with Endothelial Cells:
- Receptor activation: adhesion/binding, vasodilation.
- Activation due to complement molecules and ATP signaling.
- Receptor activation leads to vasodilation and allows for rolling and arrest of WBCs.
WBCs in Circulation:
- Neutrophils: First to adhere to endothelial cells (40-70% in humans).
- Basophils and eosinophils also potentially adhere.
- Monocytes and lymphocytes present.
Division of Labour in Immune Cells:
- Likely related to mammalian lifespans influencing cell lifespans.
- Immune cell counts alter in various diseases; CBC is the first test ordered.
Neutrophils:
- Play a major role in inflammation and response to cues.
- Path to the site of inflammation created by degrading extracellular matrix proteins.
- Sequence of events: inflammation, tissue resident immune cell activation, chemical signals, receptor activation, vasodilation, neutrophil rolling, arrest, and extravasation.
Platelets & Inflammation:
- Platelets clot blood vessels, producing prostaglandins and 5HT.
- Basophils prevent clotting with heparin to allow immune cell access.
- Stable state reached quickly, allowing platelets to dominate.
Neutrophil Functions:
- Secretion of degradative enzymes, oxidative processes, and phagocytosis.
- NETosis: Neutrophil Extracellular Trap - a unique neutrophil death process.
Regulation of Neutrophil Activities:
- Degradative enzyme regulation, short neutrophil lifespan (2-3 days), macrophage clearance.
- DNAses and macrophages clear NETs, regulating inflammation.
Other Immune Cells:
- Eosinophils, basophils, and mast cells respond to pathogens, associated with allergies.
- Mast cells found in lungs may indicate asthma.
Session 2: Paper Discussion
- Functional Role of Type I and Type II Interferons in Antiviral Defense.
- Goal of the experiment: “To be written…”