It is an exaggerated response to a harmless antigen that results in injury to the tissue, disease, or even death.

Cell-bound antibody reacts with antigen to release physiologically active substances.

Antigen-specific IgE is bound to mast cells.

Antigen bridges adjacent antibody molecules, causing disruption of the cell membrane with release of mediators.

Those in which free antibody reacts with antigen associated with cell surfaces.

Antibody is directed against cellular antigens.

Complement is activated, and target cells are destroyed.

Antibody reacts with soluble antigen to form complexes that precipitate in the tissues.

Soluble antigens combine with antibody to form immune complexes.

This sensitized T cells rather than antibody are responsible for the symptoms that develop.