Hypersensitivity reactions II Flashcards
what is type II hypersensitivity also known as
cytotoxic hypersensitivty
what are antibodies directed against antigens on
SPECIFIC cells/tissues
what antibodies are involved in type II
IgM and IgG
2 consequences of antibody binding to cell surface antigen
Complement is activated
antibody-dependent cell-mediated cytotoxicity
3 things that happen here once complement is activated
cell lysis
deposition of complement components (opsonisation)
macrophage and neutrophil activation (lysosomal content released - damage)
examples of type II hypersensitivty reactions
blood transfusion
Haemolytic disease of the newborn
Hyperacute graft rejection
Reactions to tissue antigens
what is Haemolytic disease of the newborn
condition that occurs when a mother’s antibodies cross the placenta and attack the red blood cells of her baby. This happens when the mother has a different blood type from her baby, and her immune system produces antibodies against the baby’s red blood cells.
example of a Type II hypersensitivity reaction which is a reaction to tissue antigens
Goodpasture’s syndrome (antibodies target basement membrane collagen) - immune system attacks the lungs and kidneys
whats HDN due to
rhesus incompatibility
how much of population is Rh+ and Rh-
Rh+ = 85%
Rh- = 15%
what antibodies are not normally present in Rh- people
antibodies to Rh antigens
what type of antibodies are RH antibodies
IgG
what are the antibodies called that are produced by the immune system in response to exposure to Rh-positive red blood cells
anti-Rh antibodies
3 effects of anti-Rh antibodies
spontaneous abortion
baby born with mild jaundice
baby born with Haemolytic Disease of the Newborn
how to prevent affects of anti-Rh antibodies
treat mother with Anti-Rh antibodies (Rhogam) within 72 hours of birth of each Rh+ child
Anti-Rh antibody will bind RBC, before B cell activation (prevents b cell activation and memory cell formation)
Immune complex mediated (type III) hypersensitivity reactions
immune complexes form in the bloodstream and deposit in various tissues, leading to inflammation and tissue damage.
immune complexes can deposit in tissues like joints, skin or kidneys
when immune complexes are deposited in tissues in type III hypersnesitvity, what happens?
immune complexes can activate complement proteins and attract immune cells such as neutrophils and macrophages. These cells release enzymes and toxic substances that can damage surrounding tissues and lead to inflammation, swelling, and pain.
e.g. of type III hypersensitivity in persistent infection
ab’s form against microbial antigens (chronic hep B - liver infection by hep b virus)
e.g. of type III hypersensitivity in autoimmunity
Antibodies formed against self antigens
Immune complexes deposited in the kidney, joint, arteries, skin, lungs
localised type III reaction example
arthus reaction (typically seen in response to the injection of an antigen (such as a vaccine) into a previously sensitized individual. The reaction can manifest as a raised, red, and painful lesion at the site of injection, and may also involve swelling, fever, and tissue necrosis)
generalised localised type III reaction example
serum sickness - in response to the administration of a foreign protein, such as a medication or antiserum, that triggers the production of antibodies (fever, joint pain, rash, swelling)
when does the arthus reaction appear
4-8 hours after injection (intradermal, subcutaneous) of an antigen into an animal with high levels of specific circulating antibody
3 things arthus reaction leads to
Leads to complement activation (C3a, C5a) , mast cell degranulation, neutrophil chemotaxis
in arthus reaction what leads to release of lytic enzymes and resultant tissue damage
neutrophils unable to phagocytose immune complexes
Intrinsic allergic alveolitis (give 2 examples)
An occupational disease due to inhalation of immunogenic proteins or spores
Examples :
Farmer’s Lung
mushroom worker’s disease
coffee worker’s disease
cheese worker’s disease
what does farmers lung begin with in winter
mild cough
what causes farmers lung
sensitisation to spores of thermophilic actinomycetes which grow in damp hay.
what precipiate over time in lungs in farmers lung, which activate complement (inflammation) and cause fibrosis
Immune complexes (IgG/antigen)
treatment for farmers lung
early diagnosis and avoidance
corticosteroids
when does delayed type IV hypersensitivity reaction occur
when T cells in the immune system react to an antigen, resulting in inflammation and tissue damage
how long can delayed type IV hypersensitivity take to develop
Takes 12 hours to develop
But can develop within 72 hours or after
weeks of exposure
2 things delayed type IV hypersensitivity is mediated by
T lymphocytes and macrophages
whats the tuberculin test
a type of delayed-type hypersensitivity (DTH) test used to determine if a person has been exposed to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB)/exposed to BCG vaccine
what is contact hypersensitivity
Dermatitis caused by exposure to: biological stains, hair dyes, poison ivy, nickel salts, mercuric salts (tattoos)
what type of immune response is contact hypersensitivity
T-cell-mediated immune response that occurs when the immune system reacts to an allergen.
What do t cells release in contact hypersensitivity which recruit eosinophils and mast cells that cause inflammation, itching and redness
cytokines
Coeliac Disease
A chronic condition of the upper small intestine caused by a reaction to gluten (antigen is gliadin)
2 consequences of increased t lymphocytes and macrophages in coeliac disease
Villous atrophy in small bowel (damaged villi)
malabsorption of food
