A 22-year-old woman ate some seafood. 5 hours later her torso and distal parts of her limbs developed small itchy papules which were partially fused together. One day later the rash disappeared spontaneously. Specify the hypersensitivity mechanism underlying these changes:

Answer options

1. Cellular cytotoxicity
2. Immune complex hypersensitivity
3. Atopy (local anaphylaxis)
4. Antibody-dependent cell-mediated cytolysis
5. Systemic anaphylaxis

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.