03-22-2008, 10:05 PM
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Newbie
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Join Date: Nov 2007
Posts: 6
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Thanks!!
I tnink I can manage that ! 
thank u ...but its kind difficult to remember graves and myasthenia in Type II.
I found some q? that may help too...
A 26-year-old systems analyst presents for evaluation of a bee sting allergy. He describes an episode in which he
was stung on the forearm by a bee and, within 5 minutes, experienced pruritus, urticaria, and mild wheezing. The
effector cell in this type of hypersensitivity is a(n)
A. eosinophil
B. mast cell
C. megakaryocyte
D. neutrophil E. TH1 CD4+ lymphocyte
Explanation:
The correct answer is B. This patient is experiencing the early phase of type I hypersensitivity, characterized by
pruritus and watery discharge from the nose, bronchospasm, mucus secretion in the airways, and a
wheal-and-flare response with pruritus in the skin. The mechanism of hypersensitivity involves prior sensitization
of a population of TH2 cells that produced cytokines, including interleukin-4. The interleukin-4 causes B cells to
switch their heavy chain class from IgM to IgE. The IgE molecules then attach to mast cells or basophils. With
subsequent antigen (allergen) challenge, the mast cells degranulate and release mediators, including
histamine, which produces the anaphylactic response.
Eosinophils (choice A) are involved in type I hypersensitivity reactions as well as type II antibody-dependent cell
cytotoxicity reactions directed against parasites. Eosinophils enter the area of the reaction due to the release of
eosinophil chemotactic factor (eotaxin) and the beta-chemokine RANTES released from TH2 CD4+ cells and
mast cells. Eosinophils are recruited into the tissues as part of the late-phase reaction of type I hypersensitivity.
Their survival in tissue is dependent upon IL-3, IL-5, and granulocyte-monocyte colony stimulating factor
(GM-CSF) released from TH2 cells.
Megakaryocytes (choice C) are bone marrow cells that produces platelets. They are not involved in type I
hypersensitivity.
Neutrophils (choice D) are not a cell type that is key to the development of type I hypersensitivity.
TH1 CD 4+ lymphocytes (choice E) are associated with delayed type hypersensitivity reactions such as contact dermatitis involving exposure to poison ivy or poison oak.
A Mexican immigrant presents with a 3-month history of weight loss, night sweats, a productive cough with
blood-tinged sputum, anorexia, general malaise, and a low grade fever. A PPD skin test shows > 10 mm of
induration. If the area of induration were biopsied, which of the following type of reactive cells would be found?
A. B lymphocyte
B. Eosinophil
C. Mast cell
D. Neutrophil
E. T lymphocyte
Explanation:
The correct answer is E. The CD4+ population of T lymphocytes, specifically TH1 cells, are responsible for the
delayed hypersensitivity reaction seen with a skin test in a previously sensitized patient. The clinical pattern in
the test question is classic for reactivation or adult-type tuberculosis. One of the risk factors to consider in
evaluating a patient for tuberculosis is a foreign-born patient who has recently immigrated to the U.S. A 10 mm
reaction on a skin test is considered positive if the person is in a high-incidence group (foreign born, medically
underserved, low-income population, or resident of a long-term care facility).
B lymphocytes (choice A) are involved in humoral immune reactions. Antibody production is not a feature of
tuberculosis hypersensitivity.
Eosinophils (choice B) are important in type I hypersensitivity reactions and in immune mediated responses to
parasitic infections (ADCC). They are not associated with tuberculosis hypersensitivity.
Mast cells (choice C) are tissue cells which are involved in type I hypersensitivity reactions. They have surface
receptors for the Fc fragment of the IgE molecule.
Neutrophils(choice D) are associated with acute inflammatory reactions. They are considered a "non-specific"
cell in that they do not interact with an antigen. The neutrophil is not a classic cell type seen in tuberculosis hypersensitivity.
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