1E - Cells of the Immune System Flashcards
cells of the mononuclear phagocyte system
- Originate in the bone marrow
- Derived from monocytes
- Play an important role in both in the innate and adaptive immune response in inflammation, tissue removing and repair
tissue macrophages and related cells are derived from
monocytes
macrophages initiate the immune response by
- Macrophages and related cells in the skin, lungs and liver conduct surveillance and if they detect pathogens or other sources of antigen, they will initiate the immune response
- Macrophages initiate the immune response by releasing chemicals (chemokines) that attract other inflammatory cells to the site (chemotaxis)
chemokines
chemicals released to invoke an immune response
regulate cells involved in the immune response
chemotaxis
attraction of inflammatory cells to the site of inflammatory response
function of macrophages
engulf damaged cells, bacteria, virus, infected cells and other foreign material
phagocytosis
engulfing damaged cells, bacteria, virus, infected cells and other foreign material
phagocytosis in the macrophage
- The engulfed material in a phagosome joins with a lysosome to become a phagolysosome
- Inside the phagolysosome that material is degraded into smaller pieces = antigen processing
- They present the smaller pieces (antigens) to cells of the adaptive immune system (usually a T-cell) = antigen presentation
antigen processing
Inside the phagolysosome that material is degraded into smaller pieces
antigen presentation
They present the smaller pieces (antigens) to cells of the adaptive immune system (usually a T-cell)
osteoclasts
part of the mononuclear phagocyte system and help remodel bone
giant cell formation
• Macrophages often form giant cells
◦ (With bones) to remodel bone
◦ Giant cell formation also occurs in some cases of disease (tuberculosis)
dendtritic cell
conduct surveillance in tissues that contact the environment
• Originate in the bone marrow
• Important in antigen presenting cells
• Dendritic cells are the most important cell for initiating the primary immune response to protein antigen
locations of the dendritic cell
◦ Found in the ‣ Nose ‣ Lungs ‣ Stomach ‣ Intestines ‣ Skin (lagerhands cells)
migration of the dendritic cell
to the regional lymph nodes and present the antigen to the cells of the adaptive immune system (T and B lymphocytes)
neutrophils
the first cells to arrive at the site of injury = first responders
• Important in the innate response but work even better if activated by the adaptive immune response
◦ Phagocytic
◦ Short lived in tissue
◦ Arrive in large numbers → purulent discharge
◦ Commonly associated with bacterial infections
Neutrophils are “granular” leucocytes
polymorphonuclear grandular cells
(Poly=many, morpho=shape) (H&E stain) (H→ purple) (E→ pink)
granules of the neutrophil
- The granules of the neutrophil are field with enzymes, antimicrobial peptides and proteins
- The granules in neutrophils do not stain (neutral)
hematoxylin
stains nucleic acid (basophilic - purple)
eosin
stains cell proteins (acidophilic - pink)
extravasation
move out of the blood and into the tissues
neutrophils elimination of foreign material
Neutrophils kill microbes and tumor cells and eliminate foreign material by phagocytosis
• Foreign material is digested in phagolysosome
• Neutrophils release the contents of their granules into the tissues surrounding the injury
◦ Sometimes this can cause damage to healthy tissue too
Eosinophils
polymorphonuclear granular leucocytes
• Eosinophils increase in the blood in parasitic and allergic disease
• Attracted to the site of inflammation by histamine
• Release of inflammatory granules can cause extensive tissue damage (eosinophilic granulomas in horses)
histamine
?
Eosinophils stain
• The granules in eosinophils take up the eosin when stained with hematoxylin and eosin (H&E) = hot pink
basophils
polymorphonuclear granular leucocytes
• These cells are very important in allegoric reactions
• Granule in basophils take up the hematoxylin and stain dark purple
◦ The granules obscure the nucleus
• Rarely seen in blood films
mast cells
normally reside in the tissues and are not normally found in the blood
• Release histamine and other (preformed) key mediators of inflammation
• Larger than basophils
• Mast cells have metachromatic granules that stain bright blue with a special stain called toluidine blue
chemical mediators
Many chemical mediators activate mast cells and many chemicals are produced by mast cells to activate more cells
Natural killer cells
Natural Killer (NK) cells are mononuclear but have granules smaller than monocytes but are larger than lymphocytes
• Important in the innate immune response
• Have non-specific response
• Important in early response to tumor cells and viral infections, and other intracellular pathogens
• Does not require specific antigen
difference between T lymphocytes and NK cells
Unlike cytotoxic T lymphocytes, NK cells attack cells that do not express MHC
• Virus infected cells and neoplastic cells may not express MHC and this makes them susceptible to NK attack
◦ MHC like a cell name tag, helps the immune cell to identify if the cell is self vs nonself