What is a clinical example of type IV hypersensitivity?

What is a clinical example of type IV hypersensitivity?

• A. Serum sickness
• B. Allergic rhinitis
• C. Chronic graft rejection
• D. Bee sting

Answer: (C)

Type IV hypersensitivity, also known as delayed-type hypersensitivity, involves a T-cell mediated immune response, rather than the antibody-mediated responses seen in other types of hypersensitivity reactions. In this type of reaction, the body's immune system reacts to a previously encountered antigen after a longer period, typically 24 to 48 hours, because it relies on T cells and macrophages rather than antibodies. Chronic graft rejection is a prime example of type IV hypersensitivity. In this situation, the immune system recognizes foreign tissues in a transplanted organ as non-self. It mounts a response, primarily through T cells, which slowly damages the transplanted tissue over time. The infiltration of T cells and macrophages leads to chronic inflammation in the graft, resulting in tissue damage and loss of function. In contrast, other options represent different hypersensitivity mechanisms: serum sickness involves antibody-mediated responses (type III), allergic rhinitis is a result of IgE-mediated responses (type I), and a bee sting reaction may trigger an immediate IgE response as well (type I). Understanding these classifications helps in recognizing how the immune system uniquely responds to various antigens and triggers differing clinical manifestations.

Type IV hypersensitivity, also known as delayed-type hypersensitivity, involves a T-cell mediated immune response, rather than the antibody-mediated responses seen in other types of hypersensitivity reactions. In this type of reaction, the body's immune system reacts to a previously encountered antigen after a longer period, typically 24 to 48 hours, because it relies on T cells and macrophages rather than antibodies.

Chronic graft rejection is a prime example of type IV hypersensitivity. In this situation, the immune system recognizes foreign tissues in a transplanted organ as non-self. It mounts a response, primarily through T cells, which slowly damages the transplanted tissue over time. The infiltration of T cells and macrophages leads to chronic inflammation in the graft, resulting in tissue damage and loss of function.

In contrast, other options represent different hypersensitivity mechanisms: serum sickness involves antibody-mediated responses (type III), allergic rhinitis is a result of IgE-mediated responses (type I), and a bee sting reaction may trigger an immediate IgE response as well (type I). Understanding these classifications helps in recognizing how the immune system uniquely responds to various antigens and triggers differing clinical manifestations.