Exam 3 Flashcards
(199 cards)
Mast cells
Highly granulated tissue resident cells containing surface expressed FC-epsilon receptor I. Found in mucosa in connective tissue, responsible for maintaining integrity of tissue and altering the immune system of localized trauma.
• cross bound to IgE
Eosinophils
Tissue resident granulocytes that stain heavily with eosin, Principal cause: Id airway damage, chronic asthma 
Basophils
Least numerous of all granulocytes. Secrete Th2 polarizing cytokines, IL-4, IL-13 which stimulate IgE 
Type I hypersensitivity: immediate
• IgE, Th2 cells
• mast cells, eosinophils, basophils, and their mediators (lipid, cytokine, etc)
• wheal and flare response
• atopy: predisposition to IgE mediated sensitization
• Pollen, food, venom, drugs
Type II Hypersensitivity: antibody mediated
• IgM, IgG, against cell surface ECM antigens
• opsonization and phagocytosis
• Complement and FC receptor mediated recruitment and activation of leukocytes (neutrophils, macrophages)
• abnormal cell function (neuro blockade) 
Type III hypersensitivity: Immune complex mediated
• immune complex is circulating antigens
• IgM, IgG
• Complement and FC receptor mediated recruitment an activation of leukocytes
Type IV hypersensitivity: T-cell mediated
• CD4+ T cells (Th1, Th17)
• Cytokine mediated inflammation and macrophage activation
• CD8+ CTLs
• Direct target cell killing, cytokine-mediated inflammation
Immediate hypersensitivity
Allergen + B cell —> presents to Th2 cell —> makes memory cell + plasma cell —> sensitizes mast cell —> allergen re-presented —> granulocyte response
Contents of mast cell granules 
Enzyme: tryptase, chymase, cathepsin G, carboxypeptidase
Toxic mediator: heparin, histamine
Cytokine: TNF-alpha 
Prevention of hypersensitivity I
Desensitization: Serial application of allergens in gradually escalating doses
Anti-IgE antibodies: expensive, not worth 
Examples of type II hypersensitivities
• Goodpasture’s syndrome
• Graves’ disease
• Myasthenia gravis
• Erythroblastosis fetalis
Immune complexes (type III)
• formed between antibody and antigen, get deposited in tissues
• ICs Result from: persistent infection, inhalation, auto immune disease, cryo-globulins
Diseases that result from type III hypersensitivities
Auto immune diseases: SLE, rheumatoid arthritis, multiple sclerosis
Drug allergies: penicillin and sulfonamides, serum sickness
Infectious diseases: post streptococcal, glomerulonephritis, meningitis, hepatitis, mononucleosis
T cell mediated inflammatory response (CD4+, type IV)
• most destructive, requires antigen specific effector T cells to activate macrophages (Th1)
• Antigen presenting cells: macrophages, Langerhans cells
Contact hypersensitivity (Type IV)
• Eczematous skin reaction
• Nickel, rubber, dyes, fragrance, plants
• Haptens: Small sensitizing agents that penetrate skin (help bind self-peptide to MHC class II making it immunogenic)
Dinitrochlorobenzene (DNCB)
Hapten from plants that sensitizes nearly everyone (poison ivy/oak/sumac) 
Granulomatous hypersensitivity
• tuberculin — TB test is an example of type IV hypersensitivity
• also leprosy, Crohn’s, schistosomiasis, and Sarcoidosis 
• persistence of antigen within macrophages due to killing mechanisms being blocked or particles that the cells cannot destroy
Multi nucleated giant cells
Macrophage —> epithelium’s cells
• cells that lose many functions such as mitochondria and ER, but produce a lot of TNF-alpha to continue hypersensitivity response (chronic Th1 activation)
Contact dermatitis cytokine responses
— IL-2
— IL-8
— IFN- gamma
— GM- CSF
Haptens
• Highly soluble, highly reactive, bind covalently and non-specifically to skin proteins which activates Th1 cells, CD4+ T cells in the skin (type IV)
• your hands can spread these in linear patterns and to your eyes (wherever you touch)
Pentadecacatehol
A common hapten, found in poisonous plants
Treating contact dermatitis
Corticosteroids: block the transcription of pro-inflammatory genes, and up regulate the production of inhibitors of pro-inflammatory transcription factors (Immunosuppressive)
Antihistamines: help with itching, block histamine receptors on mast cells to reduce histamine release, does not improve rash
Poison ivy
• appearance of rash two days after exposure (must be 2nd exposure at least)
• Red, raised blistering lesions of contact dermatitis
• Infiltration of blood cells into the tissue at the site of contact with the Hapten
• Death of local tissue cells, destruction of ECM = blisters 
Contact dermatitis and Th1 T cells
1.) antigen is injected into subcutaneous tissue and processed by local antigen presenting cells
2.) A Th1 effector cell recognizes antigen and releases cytokines that act on vascular endothelium 
3.) recruitment of phagocytes and plasma to the site of antigen injection causes a visible lesion