please answer all the questions and include the references: Hypersensitivity Typ
ID: 217814 • Letter: P
Question
please answer all the questions and include the references:
Hypersensitivity Type IV
1. When was the disease first described?
2. How does this disease present in a clinical setting -- what would an MD observe upon examination, what tests would be run to aid with the diagnosis, and what would those tests reveal if the results are positive?
3. Who gets this disease -- what is the rate in the general population, are there differential incidence rates based on gender, geographic location, economic status, educational status, or other variables?
4. What is the prognosis upon diagnosis -- the expected duration, and a description of the disease course throughout the rest of the life of the patient. For example, will there be progressive decline, intermittent crisis, or sudden, unpredictable crisis? Is the disease likely to kill the patient, or will they more likely die of something else? Base the prognosis on statistical evidence if it is available.
Explanation / Answer
1. The reaction was observed in 1882 by Robert Koch, but it was proved in the 1940s by Landsteiner and Chase that the reaction was mediated by the cellular and not the humoral immune system. The first DTH reaction described used only the tuberculin antigen, but the description was extended to include cell-mediated reactions to other bacterial and viral antigens, acknowledgements to the pure protein with adjuvant or haptens, and host responses to the allograft.
2. Type IV hypersensitivity reaction is described as delayed-type hypersensitivity reaction since it takes 2 to 3 days for the reaction to occur after exposure to the particular substance.
Type IV hypersensitivity reaction can occur in many parts of the body. Depending on the distinctive type of diseases, some common investigations may be necessary. Basic routine investigations may include looking at the blood function, liver function, thyroid function and kidney function.
The tuberculin test is based on a delayed hypersensitivity reaction. The test is used to determine whether an individual has been infected with the agent of Mycobacterium tuberculosis. An earlier infected person would withhold reactive T cells in the blood. In this test, little amounts of protein obtained from the mycobacterium are inserted into the skin. If reactive T cells are present—the test is positive. redness and swelling will appear at the injection site.
when a tissue sample from the position of the positive reaction is considered, it will reveal infiltration by lymphocytes and monocytes. increased fluid between the fibrous structures of the skin, and some cell death.
If the reaction is more harsh and lengthy, some of the activated macrophages will have joined collectively to form large cells containing various nuclei. An accumulation of activated macrophages is termed a granuloma.
In contact hypersensitivity, inflammation appears when the sensitizing chemical gets in contact with the skin surface.
example: a plant that can produce a contact hypersensitivity reaction is poison ivy.
3. Depending on the indications of different type IV hypersensitivity diseases, there are several risk factors as well.
Some diseases are more prevalent in women like autoimmune diseases. Some are more frequent in men such as allergic contact dermatitis. Furthermore, ethnic and geographical differences have characters to play in different diseases.
4. Type IV hypersensitivity is described by a cell-mediated response and is not mediated by antibodies like other types of hypersensitivity reactions. Particularly, the T lymphocytes are associated with the rise of the sensitivity, therefore known as cell-mediated hypersensitivity. T lymphocytes are white blood cells in the body. the T-cells will be activated once exposed to antigens by a series of biochemical events. On releasing some chemicals, the T cells stimulate other white blood cells to produce an immune response. This cascade of reactions take 2-3 days to produce and is distinct from other types of hypersensitivity reactions. Type IV hypersensitivity diseases are normally long-standing and demand on-going treatment if there is flaring up of the diseases. Nonetheless, it does not generate life-threatening diseases such as anaphylaxis or angioedema as seen in type I hypersensitivity diseases.
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