Question

Study Guide: Hypersensitivity Reactions

1.

1. What stimulates the release of molecules from mast cells during a Type I hypersensitivity reaction?a

2. Compare the role of mast cells in the immediate hypersensitivity Type I reaction to that of the role of mast cells in the late phase of the Type I hypersensitivity reaction.

1. Type IV reactions are also referred to as delayed type hypersensitivity. What immunological processes occur during the sensitization phase of a Type IV reaction compared to the effector phase?

2. Considering the relationship between these two phases, why are Type IV reactions called delayed type hypersensitivity?

Answer 1

Type 1 hypersensitivity is an immediate reaction due to IgE(immunoglobulin E mediated release of antibodies against the antigen. it causes mast cell degranulation and histamine and inflammatory mediators release.
a hypersensitivity reaction is an inappropriate response to an antigen or an allergen. type 1 reaction is an immediate reaction that involves the IgE-mediated release of histamine and other mediators from mast cells and basophils. late hypersensitivity reaction occurs within 4 to 6 hours and lasts for 2 to 3 days with less inflammation it causes direct action of sensitized T cells with stimulants and antigen. immediate-type 1 hypersensitivity is common for example hay fever, allergic conjunctivitis, and asthma.it starts within 5 to 30minutes and subsides in 60minutes.
late-phase reaction example food allergy that causes vomiting, itching, and hives.in type 1 hypersensitivity reaction IgE sensitized mast cells and produce an acute inflammatory reaction. in the late phase activated mast cells cause an inflammatory response, cells attracted to the site and activate the cells like eosinophils, neutrophils, lymphocytes, and macrophages.
it causes tissue damage.
Type IV hypersensitivity is cell-mediated immunoreaction that is due to a number of antigen-specific T cells, this reaction reaches up to 24 to 48 hours after exposure to antigen. when the cells hypersensitive to an antigen it remains the same, T cells restimulated by the antigen due to macrophages, T cells secrete cytokines that activate the lymphocytes and phagocytic cells that carry cell-mediated immune response. hypersensitivity inflammation occurs when the sensitizing products contact the skin, it reacts with proteins change as a foreign to the immune system. it changes the antigenic property of the protein, it stimulates the T cells to respond to new antigens. B and T-cells increase to some receptors as foreign. that time the immune system will not produce antibodies to react with antigens. The immune response phase is the effector phase because this reaction occurs by the direct
involvement of substance by the immune system that causes danger to the host. this reaction is immunologic specific that involves a sensitization phase and an effector phase. when the over sensitization occur for prolonged exposure to the antigen that develops the affector phase. type IV hypersensitivity reaction also called delayed-type hypersensitivity reaction, because it will show a reaction after 2 to 3 days after exposure to the substance. so that it is called delayed-type hypersensitivity.