Inflammation Flashcards
Function of macrophages
Phagocytosis and destruction of debris and bacteria. Long term scavengers
Process and present antigens to the immune system (professional antigen presenting cells)
Synthesise cytokines, complement complexes, clotting factors and proteases
Controls other cells by cytokine release or cell-cell interactions
Ways chronic inflammation can come about
Stem from acute inflammation if the damage is severe
De novo (no acute phase) e.g. Autoimmune (rheumatoid arthritis), chronic infection (viral hepatitis) or chronic low level irritants
Alongside acute inflammation with severe persistent or repeated infections e.g. Chronic cholecystitis
Appearance of macrophages
Foamy cytoplasm as lots of RER, large nucleus
Function of lymphocytes
Complex, many immunological functions.
B cells differentiate to plasma cells which produce antibodies
T cells involved in control and have a cytotoxic function.
Appearance of plasma cells
Lots of cytoplasm due to abundant RER
Clock-face chromatin in the nucleus
Perinuclear hof - pale area around the nucleus
Function of plasma cells
Produce and secrete antibodies
Appearance of eosinophils
Bilobular nucleus with bright pink cytoplasm : ‘sunburnt face with shades’
Eosinophils are seen in
Allergies, parasite infestations (esp in the gut), some tumours
Function of fibroblasts/myofibroblasts in chronic inflammation
Recruited by macrophages, secrete collagen
How giant cells are made
Fusion of macrophages due to frustrated phagocytosis (too much for them to phagocytose)
Appearance of giant cells
Multinucleated, horseshoe-shaped aggregation of nuclei around the outside, abundant cytoplasm in the centre.
Types of giant cell
Touton seen in fat necrosis and xanthoma. Contains fat.
Langhans seen in TB
Foreign body
Brief overview of possible complications of chronic inflammation
Tissue destruction, excessive fibrosis, impaired function, atrophy
Microscopic and macroscopic description of chronic cholecystitis
Macro - fibrotic, redness of wall, white mucosa, multiple gallstones
Micro - Thickened muscle, lots of plasma cells, lymphocytes
Describe the cause of chronic cholecystitis
Gallstone becomes stuck in the cystic duct, irritating the gall bladder and causing multiple repeated episodes of acute inflammation
Difference in cause between acute and chronic gastritis
Acute - alcohol/drugs e.g. NSAIDs
Chronic - Heliobacter pylori
Microscopic and macroscopic appearance of gastric ulceration
Punched out area of necrosis with a central ulcer
Polymorphs and fibrin in the centre, lymphoid infiltrate
What is a fistula?
Abnormal connection between two epithelial-lined organs (usually when tubular)
Localised and systemic effects of rheumatoid arthritis
Localised - joint destruction
Systemic - affects other organs, rarely causes amyloidosis
What is a granuloma?
Aggregate of activated macrophages. Modified and immoveable. Other inflammatory cells can be involved.
Causes of granuloma
Mild irritants - artificial joints which have broken/ruptured silicone implant
Infections - mycobacterium (TB/leprosy), other (fungi, rare)
Unknown - sarcoidosis, Wegener’s granulomatosis, Crohn’s disease
Cardinal signs of inflammation
Rubor, calor, dolor, tumor and loss of function
Describe the changes to blood flow in acute inflammation
Transient vasoconstriction of arterioles
Vasodilation of arterioles then capillaries, increasing blood flow which causes heat and redness.
Increased permeability of blood vessels causing exudation of protein-rich fluid and slow circulation as blood is thicker.
Vascular stasis
Describe the meaning of vascular stasis
Concentration of erythrocytes increases
Function of histamine
Vascular dilatation, transient increase in vascular permeability and pain.
Cells which produce histamine
Mast cells, basophils, platelets
An increase in what two types of pressure causes fluid to move out of capillaries?
Hydrostatic pressure
Colloid osmotic pressure
Describe the changes in acute inflammation that cause oedema.
Arterial dilation increases hydrostatic pressure and permeability causing loss of protein.
Net flow is out, causing oedema.
What resolves oedema?
The lymphatic system
Describe Starling’s law
The stroke volume of the heart increases in response to an increase in blood filling the heart when all other factors remain constant, as it increases stretching of the ventricular wall.
Describe the difference between transudate and exudate.
Transudate - protein rich, caused by heart failure or venous outflow obstruction.
Exudate - protein rich, seen in inflammation.
Describe different mechanical causes of leakage from capillaries.
Endothelial control, gaps formed - histamine/leukotrienes
Cytoskeletal reorganisation causing gaps to form - cytokines e.g. IL-1/TNF
Direct injury e.g. burns/chemicals
Leukocyte-dependent injuries as polymorphs produce toxic oxygen species and enzymes
Increased transcytosis by channels across the endothelium - VEGF (endothelial growth factor)
What protein covers an ulcer to prevent leakage?
Fibrin
Describe the process of diapedesis of neutrophils
Margination of neutrophils due to stasis.
They roll along with intermittent sticking, then adhesion occurs so they stop rolling.
Emigrate through the wall to tissue space - extravasion.
Able to escape as inter-endothelial cell junctions relax, digest basement membrane and move.
Describe chemotaxis and give examples of chemicals which allow it.
The movement along a concentration of chemoattractants. Receptor-ligand binding causes rearrangement of the cytoskeleton, producing a pseudopod.
e.g. C5a (active complement fragment), LTB4 (a leukotriene) and bacterial peptides (context dependent).
What does complement do?
Forms a tube which punches holes in bacteria, causing death.
C5a etc are produced as by-products.
Describe the function of Fc
Fixed complement on antibodies, always the same.
Allows neutrophils to recognise anything with antibodies bound.
Describe the role of C3b
Bonds to microbial cell surfaces and aids opsonisation by macrophages.
How are secondary lysosomes formed?
Primary lysosome fuses with a phagosome.
Describe the two types of killing mechanism utilised by neutrophils.
Oxygen dependent - superoxide, peroxidase and HOCl- (by myeloperoxidase) released into a phagosome.
Oxygen/respiratory burst
Oxygen independent - lysozyme, hydrolases, phospholipases. Bacterial permeability increase protein (BPI), catatonic proteins (defensins)
Describe the different types of chemical mediators in acute inflammation.
Proteases e.g. kinins/complement system/coagulation/fibrinolytic system. They are plasma proteins from the liver.
Exogenous e.g. endotoxin, a lipopolysaccharide produced by gram negative bacteria
Prostaglandins/Leukotrienes - metabolites of arachodonic acid from phospholipids.]
Cytokines (big)/chemokines (small) produced by white blood cells (especially macrophages) to coordinate the inflammatory response e.g. IL-1/TNF-alpha
How does oedema enhance an immune response?
Increases lymphatic drainage, delivering to the lymph nodes.
Give some complications of acute inflammation
Swelling blocks tubes e.g. acute epiglottis
Exudation causes compression e.g. cardiac tamponade: into pericardial cavity.
Or appendicitis - perforates causing peritonitis
Loss of fluid e.g. burns
Give the systemic effects of acute inflammation
Fever as endogenous pyrogens are produced - TNF alpha and IL increase production of E2 prostaglandin in the hypothalamus.
Leukocytosis as IL-1 and TNF-alpha produces accellerated release from bone marrow. Macrophages and T-lymphocytes produce CSFs.
Bacterial infections increase neutrophils and viral increase lymphocytes
Describe the acute phase response in acute inflammation.
Low appetite, high heart rate, changes to sleep.
Also changes plasma concentration of:
- C-reactive protein (activates complement system and is clinically useful)
- Alpha-1 antitrypsin (inhibits proteases)
- Haptoglobin (scavenges haemoglobin)
- Fibrinogen
- Serum amyloid A (apolipoprotein associated with HDL, can act as a chemotaxin and induce enzymes that degrade the ECM.
Describe the condition of shock
Clinical syndrome of circulatory failure, caused by widespread vasodilation and a dramatic drop in blood pressure.
What are the potential sequelae of acute inflammation?
Complete resolution
Continued acute inflammation with chronic, leading to an abcess.
Chronic inflammation and fibrous repair with tissue regeneration (scarring)
Death
Describe resolution of acute inflammation
Changes reverse and vascular changes stop.
No marginated neutrophils, permeability normal, vessel calibre normal.
Exudate is allowed to drain, fibrin broken down, neutrophils die and damaged tissues may degenerate.
If the tissue arch is destroyed, resolution is not possible.
What are the mechanisms of resolution?
All mediators have a short half life
May be inactivated by degradation e.g. heparinase
Inhibitors may bind e.g. anti-proteases
May be unstable e.g. some arachnodonic acid derivatives
Diluted in exudate e.g. fibrin degradation products
Specific inhibitors of acute inflammatory changes e.g. lipoxins/endothelin
Describe the production of prostaglandins
Phospholipids to arachadonic acid by phospholipase A2
Arachadonic acid to prostaglandins by cyclooxygenase
Describe the production of leukotrienes
Phospholipids to arachadonic acid by phospholipase A2
Arachadonic acid to leukotrienes by lipoxygenase
How do corticosteroids suppress the immune system?
Inhibit phospholipase A2 so arachadonic acid derivates cannot be made.
How does aspirin and other NSAIDs reduce a fever?
Inhibits production of prostaglandin E2
What is the most potent complement fragment?
C5a
Describe pus/abcess exudate
Creamy/white, rich in neutrophils. Typical of infection by chemotactic bacteria.
Describe haemorrhagic exudate
Many RBC, appears bloody. Indicates significant vascular damage.
Destructive infections/due to malignancy
Describe serous exudate
Plasma proteins with few leukocytes so no infection. Seen in blisters.
No fibrinogen.
Describe fibrinous exudate
Significant fibrin deposition.
Causes friction in pericardial/pleural space.
Describe the difference between a Ghon focus and Ghon’s complex in tuberculosis.
Focus - Primary site of infection in the lungs, either in the upper part of the lower lobe or lower part of the upper lobe. Inflammation.
Complex - lesion of the lung caused by tuberculosis. Have a calcified focus of infection and an associated lymph node. The centre of the focus undergoes caseous necrosis.
Describe a Ranke complex in tuberculosis.
A healed primary pulmonary tuberculosis, composed of a Ghon lesion and ipsilateral calcified hilar node.
Describe scrofula associated with tuberculosis
Lymphadenitis of the cervical lymph nodes
Give some associated complications of ulcerative colitis. (not involving the gut)
Ankylosing spondylitis Erythema nodosum Pyoderma gangrenosum Iritis Scleritis Hepatitis Cirrhosis Sclerosing cholangitis
