Immediate hypersensitivity arises when an allergic individual is exposed to an antigen (in this case referred to as an allergen) from the environment, such as a food, pollen, or the venom of an insect. In response to the allergen, the individual makes large amounts of IgE. When this happens, mast cells in tissues and basophils in the blood bind the constant end of the IgE. If that individual is exposed to the same allergen again, binding of the allergen to the IgE causes the mast cells and basophils to rapidly release a large amount of histamine. This results in symptoms such as dilation of blood vessels, inflammation, and difficulty breathing. If not treated with antihistamines, a severe allergic reaction can lead to death. It is not known why some people produce excessive amounts of IgE in response to allergens. There is some evidence for genetic factors predisposing people to allergic responses. When a person is re-exposed to an allergen, in order for the immune response to proceed as described above the IgE must already be bound to a mast cell or basophil. bind at its proper end. happen to be free in the bloodstream near where the allergen enters. not produce too much histamine, as this can harm the body.
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Part 5: Match each hypersensitivity type (1-4) with the descriptions (s) (a-k) listed below that are true about that type of hypersensitivity reaction. Some of the descriptions may apply to more than one reaction type; others may not apply to any. Enter the question number (1-4) followed by the letter of the correct answer(s) (a-k) into the answer box separated by a comma. 2 points per correct answer, 1 point will be subtracted for each incorrect answer. Example answer format: 1: R, V, T 2: Z, W 3: V, Y 1. Type I 2. Type II 3. Type III 4. Type IV a. Immune mechanisms may have evolved as a defense against helminthic parasites b. Basis of Celiac disease symptoms c. Ab mediated hemolysis as occurs in blood transfusion reactions d. Mediated by the humoral branch of immunity e. Involves IgE as principal effector f. Symptoms delayed by 24-72 hours g. Reaction to poison oak is an example h. Characterized by Ab-Ag complex activation of complement i. Inflammatory response to ragweed pollen and peanuts j. Basis of TB test k. Symptoms may occur within minutes to ~8 hours after Ag exposure
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An allergic response sometimes leads to a person’s death. How can you explain this? a. The allergen may bind to the hemoglobin, decreasing the affinity of hemoglobin for oxygen, leading to death. b. If a person has a very strong and fast response to an allergen, the tissues in the throat can swell so much in a very short time that the person cannot breathe and blood pressure may increase very quickly. Oxygen will not be carried to the brain and the person may die. c. If a person has a very strong and fast response to an allergen, the tissues in the throat can swell so much in a very short time that the person cannot breathe and blood pressure may drop very quickly. Oxygen will reach the cells at a faster rate and the person may die. d. If a person has a very strong and fast response to an allergen, the tissues in the throat can swell so much in a very short time that the person cannot breathe and blood pressure may drop very quickly. Oxygen will not be carried to the brain and the person may die.
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