physiology of white blood cells Flashcards
what are the main 2 types of lymphocytes?
B cells or T cells
what do both B cells and T cells have?
antigen specific receptors
what percentage of lymphocytes are natural killer cells?
5%
what are the key features of basophils?
- lobed nuclei and heavily granulated cytoplasm
- non-phagocytic cells
how do basophils function?
by releasing pharmacologically active substances from the cytoplasmic granules
what is the biology of basophils?
- circulate the blood
- recruited to the sites of allergic reactions or ectoparasite infection
- express FcRI
- allergen can bind to allergen-specific IgE bound to the cell surface of basophils causing degranulation of effector mediators
what are the key features of eosinophils?
- have bilobed nuclei and granulated cytoplasm
- motile phagocytic cells that can migrate from the blood into the tissues
what is the biology of eosinophils?
- majority are located in tissues
- recruited to sites of allergic reactions
- express FcRI upon activation
- granules containing toxins
- attack parasites in GI, respiratory and genito-urinary tracts
what are features of neutrophils?
- polymorphonuclear cells
- multilobed nucleus
- found in the blood
- rapidly recruited to sites of infection/injury
- short lifespan
- myeloperoxidase
what are the first responders to infection?
neutrophils
what are features of monocytes?
- kidneys shaped nucleus
- reservoir of monocytes in the spleen
- also circulate in the bloodstream where they enlarge
- migrate into tissue approximately 1 day after release from the bone marrow
- blood-borne phagocytes
what are the precursors to macrophages?
monocytes
what are the features of macrophages?
- found in tissues
- 5-10 fold larger than monocytes
- contain many more organelles compared to monocytes
- lifespan is months to years
- tissue-resident phagocytes
what are the key features of bacterial infection?
increased neutrophils (increased monocytes in chronic infection)
what are the key features of viral infection?
increased lymphocytes and sometimes increased monocytes
what are the key features of parasite infection?
increased eosinophils and activation of mast cells
what are the key features of fungal infection
increased monocytes
what are the key features of allergy?
increased basophils (and increased eosinophils in chronic phase) and activation of mast cells
why do you regulate leucocyte function?
- recruitment of leukocytes from the blood to tissues is key to their immune function
- interaction of leukocytes with blood vessel is key to this recruitment
what are cytokines?
- low molecular weight regulatory proteins or glycoproteins that act as the messenger molecules of the immune system
- they also assist in regulating the development of immune effector cells
what are cytokines secreted by?
primarily by the white blood cells
where do cytokines act?
locally - paracrine signally
what are chemokines?
a type of cytokine that induced directed chemotaxis in local responsive cells
what do chemokines function as?
attractants for leucocytes, recruiting monocytes and neutrophils to the site of infection
what is the important monocyte chemokine?
MCP-1, monocyte chemotactic protein (CCL-2)
what is inflammation?
a response to vascularised tissue to infection and damaged tissue
what is inflammation characterised by?
heat, redness, pain and swelling
what is the purpose of inflammation?
bring cells and molecules involved in host defence and repair to the site of infection/injury
what are the components of the inflammatory response?
- blood vessels
- phagocytic leucocytes
- plasma proteins
what are the 5 overview stops of the inflammatory response?
1) blood vessels dilate
2) blood vessels become more permeable
3) circulating leukocytes migrate into tissue
4) leucocytes are activated
5) activated leukocytes destroy microbes
what are the key features of acute inflammation?
- initial, rapid response
- develops within minutes
- last hours to days
- predominantly mediated by neutrophils
- resolves once the stimulus is removed
what are the key features of chronic inflammation?
- lasts weeks to months
- predominantly mediated by mononuclear cells (macrophages, lymphocytes)
- tissue destruction
- attempts at healing (fibrosis)
what are the 2 types of contact between endothelium and circulating cells?
- initial contact: P-selectin and E-selectin on endothelium recognised by oligosaccharides on leukocytes
- tighter adhesion: intercellular adhesion molecules (ICAMs) on the endothelium recognised integrins on leukocytes
what are adhering monocytes stimulated by?
MCP-1 to cross the endothelium and lodge in the intima
what is an absolute requirement for inflammation?
activated endothelium
what recruits and inflame monocytes?
adherent/activated platelets
what is the process of activation of recruited leukocytes?
- phagocytic cells can recognise, ingest and destroy many pathogens
- these cells recognise pathogens damaged host molecules by means of cell surface receptors that can discriminate between the surface molecules displayed by pathogens and host cells
- these receptors can also recognise damaged most molecules
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 the ligand for toll-like receptors (TLRs)?
range of ligands from various TLRs
what are the stages of phagocytosis?
1) occurs via actin-based mechanism and interaction with various cell surface receptors
2) foreign particles internalised to form phagosomes
3) fusion of phagosomes leads to formation of phagolysosomes where foreign particles are enzymatically degraded
what is atherosclerosis?
build-up of plaque in the lining of the arteries
what are the 3 areas of pathogenesis that are involved in atherosclerosis?
- endothelial cell dysfunction
- inflammation (mediated by monocytes/macrophages)
- dysregulation of lipid metabolism
