Which of the following is NOT a type of hypersensitivity?

Phagocytosis-mediated is not classified as a type of hypersensitivity reaction. In hypersensitivity reactions, the immune system responds excessively to a harmless antigen, leading to tissue damage. There are four recognized types of hypersensitivity:

• IgE-mediated hypersensitivity, which involves the production of IgE antibodies in response to allergens and typically results in allergic reactions.

• Cytotoxic antibody-mediated hypersensitivity, characterized by the action of antibodies against cells, often resulting in their destruction.

• Immune complex-mediated hypersensitivity, which occurs when antigen-antibody complexes deposit in tissues and provoke an inflammatory response.

• Cell-mediated (delayed-type) hypersensitivity, which involves T cell responses rather than antibodies.

Phagocytosis is a fundamental immune response used by macrophages and other immune cells to engulf and digest pathogens, but it is not classified as a hypersensitivity mechanism. It functions as a primary defense mechanism rather than an inappropriate response to an antigen.