Lecture 3.2: Immune Response Flashcards
What in the Complement Cascade causes Inflammation & Chemoattraction of Leukocytes?
C3a
C5a
What in the Complement Cascade Coats microbes with molecules recognised by phagocytes?
C3b
C3bi
Cells of the Innate Immune System
- Phagocytes
- Neutrophils
- Macrophages
- Degranulating Cells
- Natural Killer Cells (NK Cells)
What is Neutropaenia?
- Deficiency of neutrophils
- May go undetected if not severe
- In severe cases increased vulnerability to infection
- Most commonly caused by chemotherapy for cancer
Macrophage Precursor(s)
- Haematapoietic stem cells produced in the bone marrow
* Circulate in the blood as monocytes
What do Degranulating Cells do?
- Degranulation: Process by which cytoplasmic granules release their contents
- Triggered by proteins binding to IgE receptors
Basophils
- Role in the production of IgE
- Defence against viral infections
- Release heparin, histamines, serotonins
- Also capable of phagocytosis
Eosinophils
- Important in parasite clearance
- Release cytotoxins
- Present antigens to T helper cells
- Trigger mast cell histamine release
Mast Cells
- Produced in the bone marrow, circulate in the blood in their immature state
- Undergo terminal differentiation when recruited into tissues
- Release histamines, cytokines, and lipid mediators
Effects of Mast Cell Activation: What Cytokines are released?
- IL-4 & IL-13 (promotes Th2 differentiation and IgE production )
- TNF-alpha (promotes tissue inflammation)
Effects of Mast Cell Activation: What Lipid Mediators are released?
- Leukotrienes
- Prostaglandins
- Increase vascular permeability
- Cause smooth muscle contraction
- Chemoattractants for T-Cells, eosinophils, basophils, mast cells
Effects of Mast Cell Activation: Histamine
- Increase vascular permeability
* Cause smooth muscle contraction
Natural Killer Cells
- Cytotoxic Large Granular Lymphocytes (LGLs)
- Bind onto the surface of virally infected cells
- Degranulate to release substances including perforin and granzyme B
Perforin
Perforates surface of infected cell
Granzyme B
Causes cellular death by apoptosis
T-Lymphocytes
• Mature in the Thymus Gland
• Help macrophages kill intracellular microparasites by releasing Macrophage
Activating Factors (e.g. IFNγ)
• Identify and kill virally infected cells before extensive viral replication takes
place
• Similar function to NK cells, but more specialised receptors
B-Lymphocytes
• Mature in the bone marrow
• Mediate the production of antigen-specific immunoglobulin (i.e. antibodies)
• Mature cells circulate between secondary lymphoid organs in search of
antigens
