T2 L5: Physiology of white blood cells Flashcards
Give 3 examples of lymphoid cells
B-cells, T-cells and NK cells
What cell do lymphoid cells develop from?
Lymphoid progenitor
Give examples of myeloid cells
Erythrocytes, platelets, basophils, eosinophil, neutrophil and monocyte
What cell do all myeloid cells develop from?
The myeloid progenitor cell
What cell do Erythrocytes differentiate from?
Erythroid CFU
What cells create platelets?
Megakaryocytes
What cell do basophils differentiate from?
Basophil CFU
What cells do Eosinophils differentiate from?
Eosinophil CFU
What cell do Neutrophils develop from?
Granulocyte-monocyte CFU
What cells do Monocytes develop from?
Granulocyte-monocyte CFU
Give examples of phagocytes
mononuclear phagocyte, neutrophil, eosinophil
Give examples of auxiliary cells
Basophil, mast cell, platelets
What are plasma cells?
Terminally differentiated T-cells
Why are granulocytes called that?
They have granules containing important chemicals
B-cell and T-cells are part of what type of immunity?
Adaptive
What is the normal % of Neutrophils in blood?
50-70%
What is the normal % of lymphocytes in blood?
20-40%
What is the normal % of monocytes in blood?
3-10%
What is the normal % of eosinophils in blood?
1-3%
What is the normal % of basophils in blood?
<1%
What types of cells have antigen specific receptors?
B-cell and T-cells
What % of lymphocytes are NK cells?
5%. They don’t have antigen specific receptors
How do basophils appear under a microscope?
Lobed nucleus with a heavily granulated cytoplasm
What is the role of basophils?
They release pharmacologically active substances from their cytoplasmic granules
What is the mechanism of action of basophils?
They are recruited to sites of allergic reactions or ectoparasite infection and express FcεRI. When an antigen bind to the FcεRI, it causes degranulation effector mediators
What is FcεRI?
High affinity IgE receptor, allows binding to IgE
What cells is FcεRI found on?
Epidermal Langerhans cells, eosinophils, mast cells, and basophils.
What is an ectoparasite?
A parasite, such as a flea, that lives on the outside of its host
How do eosinophils appear under the microscope?
Have a bilobed nuclei and granulated cytoplasm
What is the mechanism of action of eosinophils?
They are recruited to sites of allergic reaction and express FcεRI when activated. They degranulate and the substances released attack parasites
How do neutrophils appear under the microscope?
Multilobed nucleus and pinkish
Which cells produce myeloperoxidase and reactive oxygen species (ROS)?
Neutrophils
Which cells increase in number during a bacterial infection?
Neutrophils. Increased monocytes with a chronic infection
How long is the lifespan of neutrophils?
8hr - 4days
Which cells are the first responders to infection?
Neutrophils
How do monocytes appear under the microscope?
Kidney-shaped nucleus
The spleen is a reservoir for what type of cell?
Monocytes
What is the difference between monocytes and macrophages?
Monocytes are precursors to macrophages. Monocytes are found in the blood but macrophages are tissue specific
What is the lifespan of a macrophage?
Months to years
Which cells can be referred to as tissue-resident phagocytes?
Macrophages
What are pseudopodia?
Extensions of a cell membrane
What cells increase in number during a viral infection?
Lymphocytes and sometimes monocytes
What cells increase in number during a parasitic infection?
Eosinophils and there is activation of mast cells
What cells increase in number during a fungal infection?
Monocytes
What types of cells increase in number during an allergy?
Basophils and there is activation of mast cells. Eosinophils in chronic phase.
How do cytokines generally signal?
Paracrine
What are cytokines?
Cytokines that induce directed chemotaxis
Which molecules guide monocytes into sites of
infection?
CCL-2 (chemokine ligand 2) also known as MCP-1 (Monocyte chemotactic protein-1)
What is the mechanism behind redness, heat and swelling?
Vasodilation and increased vascular permeability
Describe the inflammatory response
Blood vessels dilate and become more permeable. Leucocytes migrate into tissue, activate and then begin to destroy the pathogens
Which cells mediate acute inflammation?
Neutrophils
Which cells mediate chronic inflammation?
Macrophages and lymphocytes
What molecule stimulates adhering monocytes to cross the endothelium?
MCP-1
What are cytokines also known as?
Interleukins
What is the purpose of IgM?
It’s the first antibody produced during an immune response. Doesn’t have a high affinity so circulates in pentamers. It switches to other antibodies
What is the purpose of IgA?
The only antibody that can cross mucosal surfaces. Found in gut, tears, saliva and colostrum which helps line a babies intestines. It forms dimers and has a secretory component (s) that protects it from digestion.
What is the purpose of IgD?
Like IgM but believed to be redundant
What is the purpose of IgG?
Main mature antibody. Circulates as a monomer
What is the purpose of IgE?
For parasitic infections and allergy. Circulates as a monomer
How do white cells get into the endothelium?
P-selectin and E-selectin on the endothelium are recognised by oligosaccharides on leucocyte. ICAMS on the endothelium then recognise integrins on leucocyte. MSP-1 then stimulates cells to cross the endothelium
What is an ICAM?
Intercellular adhesion molecule
What is the function of selectins?
They bind carbohydrates and initiate leukocyte-endothelium interaction
How do platelets recruit monocytes?
Platelets directly interact with monocytes, leading to enhanced expression of proteins on the monocyte surface. This enhances platelet-monocyte aggregate formation and recruitment of further monocytes to the endothelium
Why does an increased platelet count affect leukocyte recruitment?
Platelets can bind with monocytes and cause recruitment
How do phagocytes recognise pathogens?
Cell surface receptors that discriminate between surface molecules on pathogens and host cells
Name 3 types of pattern-recognition receptors
Macrophage mannose receptor, scavenger receptors and toll-like receptors
What is the ligand for macrophage mannose receptors?
Conserved carbohydrate structures
What is the ligand for scavenger receptors?
anionic polymers, acetylated and oxidised LDL
What is opsonisation?
Coating of pathogens with circulating receptors
Describe the process of phagocytosis
Foreign particles are internalised to form phagosomes. The phagosomes fuse with lysosomes forming phagolysosomes. The foreign particles are then degraded enzymatically
Which process occurs via an actin-based mechanism and the interaction with various cell surface receptors?
phagocytosis
Name 3 pro-inflammatory cytokines
IL-1 beta, TNF-alpha and IL-6
Describe the process of atherogenesis
A damaged endothelium and deposition of lipids causes a production of chemokines and cytokines. These will recruit monocytes which will develop into macrophages and then foam cells. Alternatively, the damaged endothelium could expose collagen and that would lead to platelet activation and coagulation