Allergies Flashcards
What is a type 1 hypersensitivity? eg.?
IgE mediated immediate hypersensitivity
eg. skin allergy like sweet itch - Midge bite hypersensitivity
What is the difference between an immune response and an allergic response? Give examples of both.
Both very similar, both involve IgE
Sarcoptic mange evokes an immune response whereas cat fleas evoke an allergic response
Allergy is unregulated and an inappropriate immune response - mimics a parasite response but it is not limited to the stimulus
When is IgD produced?
Very beginning of the immune response.. stops shortly after starting
What is IgG good for?
Bacterial infection - Complement, opsonisation
How are T cells involved in the humoral response?
Help B cells switch antibody class
eg. TH2, releasing IL4, IL5, IL13 -> IgE, IgG and IgA stimulated
- Whereas TH1, releasing IFNy and TH17, releasing IL17 -> IgG only
What causes T helper cells to differentiate?
Antigen presenting cells providing signals eg. IL12 -> TH1 IL4 -> TH2 IL6+TGFb -> TH17 Vit A (Retinoic acid) + TGFb -> T-reg
Which cells down regulate the IgE/IgG/IgA response?
T-reg, IL10, TGFb, IFNy
What does TGFb stand for?
Transforming Growth Factor B
What tells APCs which cytokines to produce?
PAMPs, DAMPs, NLRs, TLRs, non infectious mediators of inflammation
Give 4 factors that influence allergy
Metabolic effects eg. very active people -> ^risk of ME
Hormonal effects eg. can grow out of an allergy, pregnancy can v allergies
Hypoxia eg. localised ischeamia (stroke/cardiac infarction)
NTs - ^ risk of depression -> ^ risk of ME
What is ME?
Myalgic Encephalomyelitis
- chronic fatigue syndrome
Are IgE levels in the blood normally high or low? Where is IgE found?
LOW in blood
Binds to FcE receptors on basophils (=mast cells) and primes them for detection of pathogens
Also found on monocytes and DCs
What is the usual half life of Igs?
Weeks/Months
What may be found histologically in allergic skin disease?
Accumulation of IgE
Where are mast cells found?
Mucosal surfaces and connective tissue
Where may IgE be found other than mast cells?
Monocytes and dendritic cells
What occurs when a mast cell encounters a parasite?
IgE crosslinked -> Mast cell degranulation - Pro-inflammaotry substances eg. > Histamine > LTs > IL4, IL5, TNFa > Eosinophil chemotactic factor > Proteases
Which cells do mast cells attract and activate?
Eosinophils
- Once activated these too will express IgE receptors and degranulate
> IL3, IL5, IL8, LTs, PAF
> Peroxidase (toxic to cells, parasites, -> histamine release from mast cells)
> Collagenase (Remodells connective tissue matrix)
> Major Basic Protein and Eosinophil Cationic Protein (Toxic to tissue cells, nerves, parasites, also -> histamine release from mast cells)
Outline the lifecycle of A. Perfoliata
Immature A. Perfoliata taken into Oribatid mite in AUTUMN, overwinters in this IH.
Horse consumes mite.
Immature A. Perfoliata attaches at Ileoceacal Junction
Matures - Gravid proglottids release eggs.
Eggs released in faeces.
What is the full name of A. Perfoliata? What is the name of the Intermediate Host?
Anoplacephala Perfoliata (cestode) - Oribatid Mite
When are young A. Perfoliata numbers in pasture high? When are they low?
Autumn
Low numbers at end of summer
What type of feeder is A. Perfoliata?
Unarmed - plug feeder
What pathological changes are seen at the site of attachment?
Gross thickening and fibrosis Erosion of epithelium Acute inflammatory response (IL1, IL6) Inflitration of leucocytes, mast cells, eosinophils Sub-mucosal oedema fibrosis (?) ^ Mucous secretion
Are A. Perfoliata eggs easy to detect?
NO
What pathological changes are seen in chronic infection?
Tissue adjacent to site of attachment - Hyperplasia of epithelium - ^ goblet cells - ^ easinophils - Hyperplasia of muscle - Modest oedema of sub-mucosa - Gut motility affected -> COLIC (blockage or ileoceacal prolapse)
How may A. Perfoliata cause colic?
Blockage or ileoceacal prolapse
Which ILs are anti parasitic?
IL13, IL4 (TH2 cytokines)
Which cytokines down regulate the immune response?
IL10, TGFb
How may parasites modulate the immune system?
Upregulate Tregs which in turn down regulates TH2s, meaning they are safe!
What does complex regulation of immune responses prevent?
Risk of autoimmunity, hypersensitivity and excessive tissue damage
