White Blood Cells and Phagocytosis Flashcards
Name some granulocytes
- Neutrophil
- Basophil (become mast cells in tissues)
- Eosinophil
What colour do basophils stain and what is their main role?
- Blue granules (H&E staining)
- 0.2-1% of all WBCs
- Enter tissues -> form mast cells
- Main role = hypersensitivity type I (allergy)
- Degranulation leads to inflammation
What colour do eosinophils stain and what is their role?
- Pink granules (H&E staining)
- In circulation (blood): 4% of all WBC
- Role in immune responses to parasites & allergies
- Release granule content to kill (bigger) target
- granules: eosinophilic cationic protein, peroxidase, MBP
Define phagocytosis
Cell eating microorganisms/other
What are the roles of phagocytosis?
- Protection from pathogens
- Disposal of damaged/dying cells
- Processing + presentation of antigens
- activation of adaptive immune system
- links innate + adaptive immunity
Neutrophils are an example of phagocytic cells. What enzymes do neutrophils use to kill microbes?
- Lysozyme
- Collagenase
- Elastase
What is the difference between monocytes and macrophages?
- Monocytes = in the blood
- Macrophage = when activated in the tissue
Macrophages secrete cytokines
Another type of phagocyte is the dendritic cell. Where are dendritic cells found and what do they do?
- Found in skin, mucosa, tissues
- Capture microbes + phagocytosis
- Not just to eliminate
- Present antigens to T cells
- Link innate + adaptive immune response
What are the 4 steps of phagocytosis?
- Phagocyte mobilization (chemotaxis)
- Recognition + attachment
- Engulfment
- Digestion: pathogen destruction
What is chemotaxis?
- AKA phagocyte mobilization
- Movement of cells towards site of infection
What is chemotaxis guided by and what are they released from?
- Guided by chemoattractants
- Released by…
- Bacteria (N-fMLP)
- Inflammatory cells (chemokines eg IL-8)
- Damaged tissues
What are the requirements in order for the phagocyte to recognise the pathogens?
- React to invading pathogens (foreign)
- No reaction to body’s own tissues (self)
What are Pathogen Associated Molecular Patterns (PAMPs)?
- Allows for recognition by phagocyte
- Structures shared by groups of related microbes
- Present on pathogens + not on host cells
- Invariant structures, shared by an entire class of pathogens
- Essential for survival of pathogens
- prevents pathogen evasion of immune responses
What are pattern recognition receptors (PRRs)? Examples?
- Present on phagocytes + other cells
- Recognise PAMPs
- Toll-like receptors
- C-type lectin receptors
- NOD-like receptors
- RIG-like helicase receptors
- Scavenger receptors
Describe Toll-like receptors (TLRs), a type of PRR
- Essential roles in innate immunity
- Conserved during evolution
- Stimulate production of inflammatory cytokines
- Human TLRs recognise PAMPs:
- lipolysaccharide (gram -)
- liptoeichoic acid (gram +)
- bacterial DNA seq (unmethylated CpG)
- single/double-stranded viral RNA
- glucans (fungi)
