Interaction of sensitized T-lymphocytes with antigen.

The binding of antibodies and antigens in the circulating blood, accompanied by the formation of immune complexes, which, with the participation of complement and phagocytes, damage the cells of the body

Binding of circulating antibodies to antigen fixed on the surface of target cells.

Binding of antibodies (IgE and IgG4) fixed on target cells to the antigen.