Path - Anatomy, Inflam and Immu - Exam 2 Flashcards
Describe possible outcomes for a cell subjected to stress - there are 3
- Adaption and improved funtion
- Reduced health followed by recovery to the same level
- With persistent stress, cell injury and/or death
Give an example of a physical, environmental, genetic and immune function stimuli that may cause cellular injury
Physical - mechanical/heat
Env. - bacterial
Genetic - inherited
Immune function - auto-immune
What is the connection between pathogenesis and morphology?
Pathogenesis causes changes in morphology
Describe features commonly found in injured cells - reversible
Swelling, cytoplasmic inclusions, accumulations and pigments, steatosis
Describe features commonly found in injured cells - irreversible
Abnormal mitochondria, irregular cell contours, eosinophilia and nuclear deformities
How can swelling of the cell occur, and what does it look like?
Can occur through failure of a membrane pump, or could be adaptive - this is called membrane blebbing and can occur in hypoxia to increase surface area, facilitating uptake of oxygen.
Swelling in toxic injury: cell looses organised structure, ribosomes detach and lipid accumulates.
Hydropic swelling makes a cell look pale and washed out
Excess liquid in cell dilates the cell substructure. ER is completely disrupted
What are inclusions?
Something that’s not usually present, and is described according to staining properties e.g. a Hyaline inclusion would be glassy and pink in appearance.
An example of an inclusion is a Mallory body, often found in alcoholic livers.
However, they can also be viral
- eosinophilic, basophilic or amphiphilic
What are accumulations?
A build up of a product of the body, which should not be there.
These can be intracellular or extracellular.
Intracellular: glycogen accumulates in the lysosome in alpha-gluconidase deficiency
Extracellular: amyloid can get deposited in the myocardium, which will eventually interfere with vascular supply
What are pigments?
Coloured substances, which can be endogenous or exogenous
Endogenous - normally present, abnormally accumulated
Exogenous: not normally present
endogenous = normally present but abnormally accumulated. Haemachromatosis - too much haemosiderin (stored iron) in liver cells
Exogenous”
- ferruginous bodies (asbestos fibbers coated in iron)
Describe Steatosis, and where it is particularly relevant
Steatosis - steahepatitis - cirrhosis - liver failure
Steatosis is the abnormal accumulation of lipid.
Organs may appear enlarged and yellow in appearance, with abnormally large lipid droplets displaying mitochondria clustered around them.
Benign in isolation, but it does sensitize cells to inflammation, which can lead to hepatitis, then cirrhosis, then fatal liver failure
Why might mitochondria appearance change, and what could this change look like?
Mitochondria can change in response to Anoxia - absence of oxygen
They become greatly swollen and lose their parallel arrays of cistaes
Why would Eosinophilia be seen in irreversible cell injury?
Denatured proteins in the cytoplasm of cells bind eosin, and less RNA production leads to loss of basophilia
What is a nuclear abnormality we might see in irreversible cell injury?
Multinucleation - nuclei divide without cell pulling them apart
What could happen to cell membranes and cell staining in irreversible cell injury?
- Irregular contours
- Eosinophillia as a result of released protein into the cell
Define necrosis
The spectrum of morphological changes following cell death or tissue death. Always a pathological process
When do you see microscopic changes in cells undergoing necrosis, and what is the sequence of nuclear changes you will see?
-4-12 hours
- Nucleus will go from normal, to Pyknosis as a result of shrinkage, darkening and condensation (black dot). From there, to Karyorrhexis, which is breakdown of the nucleus. This is followed by Karyolysis, where the nucleus is gone
- Throughout this process, the cell will become more and more eosinophilic
What are some other microscopic changes you will see in necrotic tissue?
Cytoplasmic vacuolation
Eosinophilia
Cell membrane blebbing/rupture
Describe coagulative necrosis
- Most common type
- Usually follows ischaemia, which causes an infarct (localised necrotic area). Tissue is softer than normal, and either more pale (pale infarct) or haemorrhagic (red). Over time, a haemorrhagic border will develop around a pale infarct.
- The cellular architecture is preserved, and cell outline remains for days/weeks. –There is a delayed breakdown of cells, and an inflammatory response.
- Histologically you might see pink cytoplasms still in the shape of cells, missing nuclei.
Describe colliquative necrosis
- The necrotic cell releases powerful hydrolytic enzymes, as well as inflammatory exudate - particularly neutrophils. This leads to liquefaction of the entire cells. Later on, there is an inflammatory reaction and liquid material is removed by macrophages, leaving a cystic space, often with a fibrous peripheral border.
- Cellular architecture almost completely disintegrates
- Occurs in two main settings: the brain, or an abscess cavity in the lung
Describe Caseous necrosis
-Almost exclusively in TB patients
-Has a white, cheesy appearance
Microscopically is an amorphous, granular debris, lacking in cell detail and outline. H&E sections will show eosinophilia.
-Usually have granulomatous adjacent inflammatory reactions i.e. giant cells and macrophages everywhere
-Histological sections will show the absence of cell outlines and tissue destruction
What is the difference between wet, gas and dry gangrene?
- Wet gangrene is necrosis with superadded putrefaction, usually due to gram negative bacteria
- Gas gangrene is usually due to gram-positive bacteria found in soil, like Clostridium species. It causes crepitant swelling
- Dry gangrene is essentially mummification - tissue is dry and black. Often a result of coagulative necrosis
What does fat necrosis look like from a macroscopic perspective?
Chalky deposits, as a result of released fatty acids reacting with calcium
What are the outcomes of necrosis dependent on?
The tissue involved: susceptibility to injurious stimuli and ability to regenerate, extent of necrosis, and time elapsed.
Subsequent fibrosis is often seen
What is autolysis?
Self-digestion of tissue AFTER DEATH, not technically necrosis
What is the difference between innate and adaptive immunity?
Innate immunity is immediate in response to infection, using relatively non-specific defence mechanisms. It activates and orientates the adaptive immune response.
Adaptive immunity ‘tailors treatment’
What is the innate immune response made up by?
- Physical barriers including skin and saliva
- Soluble proteins in the tissues and circulation e.g. complement and acute phase proteins
- Cellular components including neutrophils and macrophages
- Cytokines released by cells - IFN-gamma and TNf-alpha
How does the innate system recognise non-self?
Through pattern recognition receptors, which recognise altered cells, oxidised cells, oxidised membrane structures etc
In infections, patterns recognised are those conserved in non-human cells e.g. Pathogen associated molecular patterns (PAMPs)
What to Toll-like receptors (TLRs) do?
These are located on the cell surface and in walls of intracellular vesicles, particularly in macrophages and dendritic cells. They recognise a range of pathogen-associated molecules from bacteria and viruses
They activate other molecule to induce the production of PRO-inflammatory cytokines and chemotactic factors
- recognise PAMPs
- activate TF to induce pro-inflam cytokines and chemokines and IFN
What do NOD-like receptors do?
Act as intracellular sensors of bacterial infection. They’re located in the cytoplasm of cells routinely exposed to bacteria e.g. epithelial cells of the gut, dendritic cells and macrophages
Crohns = loss of function of NOD2
NALP3 - senses cellular damage (DAMPs)
What are some of the consequences of production of Pro-inflammatory cytokines (e.g. IL-1B/IL-6/TNF-a)?
Activation of complement opsonization, phagocytosis, decreased bacterial and viral replication and initiation of adaptive immune response
What do levels of C-reactive protein tell you?
This is a pro-inflammatory acute phase protein, and an important opsonin, so levels of it rise with an infection
High levels of CRP therefore tell you the body is fighting inflammation
- best marker
- produced by liver under influence of IL 6
EXCEPTIONS:
- SLE
- sjorgens
- UC
What happens to Neutrophils during inflammation/infection?
Neutrophils normally roll along a vessel’s endothelium. During inflammation, stronger adhesion molecules are expressed on endothelium, anchoring neutrophils to vessel wall. They then extravasate, squeezing between endothelial cells and traverse the basement membrane. They then ride a chemokine gradient to the site of inflammation
- P and E selectin - Sialyl Lewis - weak adhesion
- ICAM 1 - LFA-1 - extravasation
What’s the process of phagocytosis?
- Phagocyte receptors bind to microbial surface components
- Bound pathogen is internalised into a phagosome
- Pathogen is killed either by phagosome acidification or through fusion with lysosome
- Soluble debris undergoes exocytosis
What are the three major classes of innate phagocytes?
- Granulocytes: neutrophils, basophils and eosinophils. Neutrophils are recruited early and die early
- Macrophages
- Immature dendritic cells
What are the main cells involved in adaptive immunity?
T cells
B cells
Plasma cells
When does adaptive immunity kick in?
After about 12 hours, at which stage it is properly primed.
It proliferates within 1-3 days, and the makes antibodies which recognise the extracellular pathogen.
How are T-helper subsets divided?
Based on the transcription factor they carry, which dictates their function
What are the different subsets of THs?
- TH1
- caused by IL-12
- intracellular pathogens: parasites and bacteria
- autoimmunity
- delayed type hypersensitivity - TH2:
- caused by IL-4
- extracellular pathogens: viruses and bacteria
- allergy, asthma - TH17
- caused by TGF-B
- extracellular pathogens: fungi and bacteria
- autommunity - TFH - follicular
- Treg (FOXP3)
- caused by TGF-B
- immunosupression
- developed in thymus due to self tolerance
PAMP examples:
Flagellin
dsRNA
What does co-stimulation do to T-cells?
Acts as a mechanism to avoid auto-immunity
What does Tolerance do with T-cells?
Prevents auto-immunity
Central tolerance takes place in generative lymphoid organs - bone marrow and thymus.
Outcomes:
a) apoptosis
b) change in receptors
c) development of regulatory T cells = CD4+
Peripheral:
a) anergy
b) apoptosis
c) supression
What are the lymphoid organs?
Primary and secondary
- Primary - development and maturation.
Thymus and BM - Secondary - trap antigens
Lymph, spleen, tonsils, gut etc
What does the thymus do in central tolerance?
Displays peripheral tissue antigens in thymic medullary epithelial cells
AIRE = transcriptional regulation
What is the connection between B cells and antibodies?
Antibodies are only produced by B cells that respond specifically to one antigen
What are some of the effector functions of antibodies?
- Neutralisation of microbes
- Opsonization and phagocytosis of microbes
- Complement cascade activation
what is innate immunity
always present (ready to attack); many pathogenic microbes have evolved to resist innate immunity
what is adaptive immunity
stimulated by exposure to microbe, more potent
what are lymphocytes
cells of the adaptive immunity, recognise antigens and develop into cells that perform defence functions
what re antigen presenting cells
cells that capture antigens and display them to lymphocytes, interphase between innate and adaptive immunity
what are effector cells
leukocytes (white blood cells) that eliminate microbes, may be lymphocytes but are often leuockotes (e.g. phagocytes, innate immune cells)
how are lymphoid organs classified
2 groups, primary and secondary
what is the primary lymphoid organs roles
provides an appropriate microenvironment for the development and maturation of lymphocytes, bone marrow and thymus
what is the secondary lymphoid rogans role
traps antigens, generally from nearby tissues/fluid and are sites where lymphocytes can effectively interact with antigens (lymph node, spleen etc.)
helper T lymphocytes can produce ______ to have what effects
cytokines to activation macrophages, inflammation edna citation of T and B lymphocytes
what is the role of the B lymphocytes
secretion of antibodies and this causes neutralisation of microbes, complement activation and pahgocytosis
what is the role of the cytotoxic T lymphocyte and the natural killer cell
killing of the infected cell
What are needed to initiate immune responses and how
APC, co-localize with T cells and display HLA molecules that interact with T cell receptors (class 1 and class 2)
conseuqnce of mutations in AIRE
human disease, autoimmune polyendocrinopathy with candidiasis and ectodermal dysplasia, also called autoimmune polyendocrine syndrome.