Immunopathology Flashcards
What is a type I hypersensitivity?
Immediate injury caused by Th2 cells, IgE antibodies, and mast cells
What is a type II hypersensitivity?
Antibody mediated disorder, secreted IgG and IgM antibodies attack self cells
What is a type III hypersensitivity?
Immune complex (IgG and IgM) mediated disorder
What is a type IV hypersensitivity?
Sensitized T lymphocytes Th1 and Th17 cells (CTLs) cause injury
Myasthenia gravis is what type of hypersensitivity?
Type II
Graves disease is what type of hypersensitivity?
Type II
SLE is what type of hypersensitivity?
Type III
Poststreptococcal glomerulonephritis is what type of hypersensitivity?
type III
Th1 cells secrete what cytokines to induce T cell differentiation?
IFN-gamma
Why is the time important in organ transplant?
Reperfusion injury
What is an isograft?
identical twin graft
What is an allograft?
Same species graft
What is a xenograft?
Different species graft
What is the direct mechanism of transplant rejection?
Antigen-presenting cells in the graft activated class II MHC
What is the indirect mechanism of graft rejection?
Recipient’s APCs stimulate T cells
What are the two types of cells that are mainly affected in graft rejection?
Vascular and epithelial cells
What are the two humoral mechanisms of hypersensitivity?
Ab bind to HLA molecules in graft endothelium
Ag-Ab complexes form in circulation (type iII)
What are the three patterns of rejection? What is the timeframe for each?
Hyperacute (minutes)
Acute (weeks to months)
Chronic (years)
What can sensitize a patient to a hyperacute rxn?
Prior transplant
Prego
What causes the increased sensitivity in hyperacute rejection?
Preformed Abs against Ag in allografts
What are the pathological changes seen in hyperacute rxns?
Fibrinoid necrosis and thrombosis
Acute rejection is mediated by what?
Cellular, humoral, or combined mechanisms
What are the histologic characteristics of acute rejection?
Lymphocytic infiltration
Tubular necrosis
What do CD8 cells do in acute cellular rejection?
Lymphocytes infiltrate tubular and vascular BM causing tubular damage and endothelitis
What do CD4 cells do in acute cellular rejection?
help cells produce cytokines, causing interstitial inflammation
What are the two morphological patterns if acute humoral rejection?
Necrotizing vasculitis
Initimal thickening d/t accumulation of fibroblasts, foamy macrophages
What are the two possible mechanisms behind chronic rejections?
Humoral injury = proliferative vascular lesions
Cellular injury = cytokine induces proliferation of vascular smooth muscle
Is there lesser or higher requirement for immunosuppression for livers?
Lesser
What is the triad of features of acute liver rejection?
- Portal tract inflammation
- Bile duct epithelial damage
- Endotheliitis of portal vein and hepatic artery branches
What cells are involved in acute liver rejection?
Mixed inflammatory cells infiltration with eosinophils
What happens histologically in chronic liver rejection?
Progressive disappearance of bile ducts d/t direct immunologic destruction or loss of blood supply
What causes the ischemic changes seen in chronic liver rejection?
Obliterative arterities from proliferation of intimal layer
What is the end result of chronic liver rejection? (2)
Portal and hepatic fibrosis
What is the major complication with heart transplantation?
Diffuse intimal proliferation –> CAD
What happens with heart transplant rejection?
Cellular rejection with interstitial and perivascular T cell infiltrates
What does heart transplant rejection resemble histologically?
Myocarditis
What are the histological characteristics of acute cardiac rejection?
Tons of lymphocytes, with destroyed myocytes
What is graft arteriopathy?
Vascular proliferation by immune cell lead constriction of a vessel via hypertrophy
What are the infections that cause malignancies in Cardiac transplants? What causes this?
EPV B cells lymphoma from the immunosuppression
What does transplantation of hematopoietic cells treat? (3)
- Hematological disorders
- Non-hematologic malignancies
- Immunodeficiency
What is GVHD?
Donor T cells recognize the host HLA antigens as foreign, and mount a type IV reaction against graft elements and tissues
What are the usual targets of GVHD?
Epithelial skin
GIT
Liver
Asthma is what type of hypersensitivity rxn?
Type I
Bronchial asthma is what type of hypersensitivity rxn?
Type I
Allergic rhinitis is what type of hypersensitivity rxn?
Type I
Food allergies are what type of hypersensitivity rxn?
Type I
What portion of immunoglobulins bind to phagocytes?
Fc bit
What are the three ways in which antibodies in type II hypersensitivity reactions cause cell damage?
Phagocytosis
Complement activation
ROS production
What are the antigen involved in SLE?
Nuclear antigens
What are the major clinical manifestations of SLE?
Nephritis, skin lesions, arthritis
What is the MOA of type IV hypersensitivity?
APCs present tissue antigen to CD8 (or CD4) cells, causing activation of T cells
What is the specificity of T cells in RA?
Collagen/circulating self proteins
What is the principal MOA of RA?
Inflammation mediated by Th17 cytokine releasing
What are the clinical manifestations of RA?
Chronic arthritis with inflammation, destruction of articular cartilage
What is the cell mediated cytotoxicity in type IV hypersensitivity rxns?
host cytotoxic lymphocytes destroy graft parenchymal cells,
What is the MOA of delayed type hypersensitivity?
Helper lymphocytes secrete cytokines, causing recruitment of PMNs
What do CD8 cells stimulate? CD4?
CD8 = CTLs CD4 = Activated macrophages, B cells
What do CD4 cells secrete to stimulate macrophage action/activation?
IFN-gamma
What are the two main types of hypersensitivity reactions involved in graft rejection?
Type II
Type III
How do you avoid hyperacute rejection?
Cross-matching recipient MHC with donor lymphocytes
What are the gross characteristics of graft rejection in a kidney?
Areas of infarct/hyperemia
What are the histological changes seen in acute rejection?
Fibrinoid necrosis and thrombosis
What type of hypersensitivity are involved in acute rejection?
II, III, and IV
What are the gross characteristics of acute rejection?
Hyperemia
What is the MOA of acute cellular rejection?
CD8 lymphocytes infiltrate BMs
CD4 cells produce cytokintes
What are the cells types involved in acute cellular rejection? (4)
T cells
B cells
Macrophages
lymphocytes
What are the two morphological patterns seen in acute humoral rejection?
- Necrotizing vasculitis
2. Intimal thickening d/t accumulation of cells
What are the two possible mechanisms of chronic rejection?
Humoral injury
Cellular injury
What is the morphology seen in chronic rejection?
Vascular changes
Interstitial fibrosis
Chronic inflammation
Which types of hypersensitivity rxns occur with heart transplants?
Type II, III, IV
What is the MOA of cyclosporin? (what does it block, and what is this needed for)?
Blocks nuclear factor of activated T cells (NFAT), which is ncessary for IL-2
What is the MOA of steroids in immunosuppressive therapy?
Suppress macrophage activity
What is the triad of symptoms seen in acute GVHD?
Dermatitis
Enteritis
Hepatitis
What are the symptoms of chronic GVHD? (3)
FIbrosis of the dermis
Esophageal stricture
Liver/bile damage
What is the MOA of primary graft failure?
Host natural killer cells or T cells survive irradiation