Unit 4 Lec 4 Flashcards
(35 cards)
What type of hypersensitivity reaction is T cell mediated?
Type IV
What type of hypersensitivity reactions are antibody mediated?
I, II, III
What type of immune response causes tissue injury and disease?
Hypersensitivity reactions
What are three mechanisms in which the immune response can cause tissue injury?
Reactions against microbes
Reactions against environmental antigens
Autoimmunity (reactions against self-antigens)
In what way can immune reactions against microbes cause hypersensitivity?
Immune response is excessive (usually if microbe is persistanct
- TB persistance– Ongoing T cell response– Granuloma formation
Antibodies produce antibodies that bind to antigen and form IMMUNE COMPLEXES that deposit in tissues lead to INFLAMMATION
- Post streptococcal glomerulonephritis
Antibodies or T cells against a mircrobe can cross react with normal tissue cells
- Rheumatic heart disease
How much of the population has an immune reaction against environmental antigens?
20 percent have abnormal responses to one or more of these substances
- Allergies to pollen, animal dander, and dust mites
What consitutes autoimmunity?
Failure of normal mechanism of self tolerance– immune reactions against self antigens
- 5 percent general population, common in age groups 20-40
- Varied in severity
What are the mechanisms of tissue injury in the mechanisms and classifications of hypersensitivity reactions?
Tissue injury is caused by the same mechanisms that are used to eliminate infections
- Reponse is triggered but maintained inappropriately
What is the mechanisms of Type I hypersensitivity?
Pathologic mech IgE
Tissue injury mech: Mast Cells and Mediators (vasoactive amines, lipid mediators, cytokines)
What is type Ii hypersensitivity?
Antibody mediated (IgM, IgG against cell surface or extracellular matrix antigens)
- Opsonizaiton and phagocytosis of cells is mechanism for tissue injury
- Complememtn and Fc receptor mediated recruitment and activation of leukocytes
What is type IV hypersensitivity?
Type IV T cell mediated
CD4 (cytokine mediated)
CD8 CTL (T cell mediated cytolysis)
- Recruitment and activation of leukocytes
Direct targeting cell killing cytokine mediated inflammation
What is seen in goodpastures syndrome?
Glomerulonephritis induced by antibody against the glomerular basement membrane
- Glomerular inflammation and severe damage
SMOOTH LINEAR DEPOSITS OF ANTIBODY ALONG THE BM
What is systemic lupus erythematosus?
Type III hypersensitivy where immune complexes deposit on glomerular basement membrane showing neutrophilic inflammation
- COARSE GRANULAR DEPOSITS OF ANTIGEN ANTIBODY COMPLEXES
What is seen in autoimmune hemolytic anemia?
IgG against protein antigens on surface of RBCs
- Idiopathic (associated with lymphoma or leukemia)
Treatment
- Immunosuppression (glucocorticoids)
- Others including anti-CD20 (B cell) rituximab
- May need splenectomy
What are the effector mechanisms of type II?
Opsonization
Antibody deposition in tissues
Antibody binding to cellular receptors or proteins
- Usually affect the cells tissues where the antigen is present rather than systemic
How does opsonizaiton work in hypersensitivy reactions?
Directly or indirectly through complement activation (phagocytosis (receptors for Fc portion of IgG and complement proteins)
- Autoimmune hemolytic anemai
- Autoimmune thrombocytopenic purpura
- Hemolysis in transfusion reaction
What happens in Antibody deposition of tissues in hypersensitivity reactions?
Recruitment of neutrophils/macrophages— mediator release (lysozyme, reactive oxidative species)
- Inflammation and tissue injury (Glomerulonephritis, Goodpastures syndrome, Acute rhemuatic fever)
- Complememtn by products C3a C5a activate neutrophil
What happens in abnormal physiologic responses without cell tissue injury?
Antibody stimulates receptor without ligand or antibody inhibits binding of ligand to receptor
- Myasthenia gravis and Graves’ disease are examples
What is the most common cause of acquired valvular heart disease?
Rheumatic heart disease
Occurs as antibodies againsT GAS antigens cross react with host antigens (molecular mimicry)
- Strep M protein and Myosin share similar epitopes
What is the most common cause of poststreptococcal glomerulonephritis?
Most common cause of acute nephritis worldwide
- Patients have low serum c3
- Occurs after skin or throat infection with certain strains of group a streptococc
- CLinical presentation ranges from asymptomatic microscopic hematuria
What are particulary susceptible locations for Type III hypersensitivity?
Vasculitis, nephritis, vasculitis
- Due to that plasma is ultrafiltrate in glomeruli and synovia of joints
What is the arthus reaction?
Localized form of immune complex mediated vasculitis
- Antigen injected subcutaneously into previoulsy immunized animal
- Immune complexes deposit in the walls of small arteries at the injection site
- Local cutaneous vasculitis with tissue necrosis
What happens in serum sickness?
Systmeic immune-complex mediated reaction
Named after reactions to administration of horse anti-serum to treat pneumococcal infections
- Starts 7-10 days after exposure (time needed for IgG response)
- Symptoms are fevers chills rash arthritis glumerulonephritis
What is serum sickness an example of?
Transient immune complex mediated syndrome
