Immunopathology Type 2, Autoimmunity Flashcards
Describe the molecular and cellular details of the immunologic mechanisms by which tissue damage occurs in a Type II (“cytotoxic antibody”) reaction.
Immunopathology is due to the actions of abs (IgG, IgA, or IgM) directed against a specific target tissue or cell.
Mechanisms:
Complement-mediated damage: Tissues against which abs are made can be damaged by lysis, phagocytosis, or by release of the phagocytes lysosomal enzymes and reactive oxygen species.
Stimulatory hypersensitivity: Ab may behave as an agonist at the receptor on a tissue, but won’t be subject to the normal feedback controls that an endogenous ligand would be.
Give an example of a Type II mechanism disease of muscle, kidney, heart, red cells, platelets, lung, thyroid, pancreatic islets.
Muscle: Myasthenia Gravis
Kidney: Goodpasture Syndrome
Heart: Dressler Syndrome, Rheumatic Heart Disease
Red Cells: Autoimmune Hemolytic Anemia
Platelets: Autoimmune Thrombocytopenic Purpura
Lung: Goodpasture Syndrome
Thyroid: Grave’s disease, Hashimoto’s thyroiditis
Pancreatic islets: Abs provide prognositic info about type I diabetes, but are not thought to be pathogenic.
Describe the fluorescent antibody tests which would allow you to make the diagnosis of Goodpasture’s Syndrome, given: patient’s kidney biopsy, normal kidney biopsy, patient’s serum, and fluoresceinated goat antisera to human IgG and complement.
In Goodpasture syndrome, antibody directed along the basement membrane, not trapped in clumps, so the staining by immunofluorescence is sharp and linear.
Distinguish between the “lumpy-bumpy” and “linear” immunofluorescent patterns in terms of the most probable immunopathologies they represent.
Lumpy-bumpy: Type III
Linear: Type II
Describe how antibody-mediated tissue damage could result from:
The innocent bystander phenomenon
Cross-reaction of a foreign antigen with self
Coupling self antigen with a foreign antigenic “carrier”
Exposure of a sequestered antigen
Inadequacy of regulatory T cells
“innocent bystander”: Damage to normal tissue, which happens to be associated with or infected by the antigen (which is truly foreign).
Cross-reaction of a foreign antigen with self antigen:
