After sensitization a test animal received subcutaneously a dose of antigen. At the site of injection a fibrinous inflammation developed with alteration of vessel walls, basal substance, and fibrous structures of connective tissue. The inflammation took form of mucoid and fibrinoid degeneration, fibrinoid necrosis. What immune response occurred in the test animal?

Answer options

1. Granulomatosis
2. Transplantation immune reaction
3. Immediate hypersensitivity
4. Normergic reaction
5. Delayed hypersensitivity

Explanation

In type 1 hypersensitivity, B-cells are stimulated (by CD4+TH2 cells) to produce IgE antibodies specific to an antigen. The immediate hypersensitivity reaction occurs minutes after exposure and includes the release of vasoactive amines(histamine) and lipid mediators. Histamine causes bronchoconstriction, mucus secretion, vasodilatation, vascular permeability.TYPEMECHANISMEXAMPLESType I - AnaphylacticAn antigen reacts with IgE bound to mast cells• Anaphylaxis • Atopy (e.g. asthma, eczema, and hay fever)Type II - Cell boundIgG or IgM binds to an antigen on the cell surface• Autoimmune hemolytic anemia • ITP • Goodpasture's syndrome • Pernicious anemia • Acute haemolytic transfusion reactions •