Answer:
Contact dermatitis due to poison ivy is mediated by an immune response called allergic contact hypersensitivity (ACH). When a person comes into contact with the oily resin called urushiol found in poison ivy, poison oak, or poison sumac, it can trigger an immune reaction in the skin
Step-by-step explanation:
Here is a step-by-step explanation of how ACH is mediated:
1. Contact with urushiol: When a person touches poison ivy, urushiol from the plant's leaves, stems, or roots can get onto their skin. Urushiol is a potent allergen that causes an allergic reaction in most people.
2. Penetration and binding: Urushiol easily penetrates the outer layer of the skin and binds to proteins in the skin cells. This forms a hapten-protein complex, which acts as an antigen, triggering the immune response.
3. Antigen presentation: The hapten-protein complex is recognized by specialized immune cells called antigen-presenting cells (APCs), such as dendritic cells. These cells engulf the complex and process it into smaller peptides.
4. Activation of T cells: The processed peptides are presented on the surface of the APCs, where they can be recognized by specific T cells called helper T cells (Th cells). Th cells play a crucial role in coordinating the immune response.
5. Release of cytokines: Upon recognition of the antigen, Th cells release signaling molecules called cytokines. These cytokines recruit other immune cells, such as inflammatory cells, to the site of contact with the poison ivy.
6. Inflammation and immune response: The recruited immune cells release additional cytokines, triggering an inflammatory response. This leads to the characteristic symptoms of contact dermatitis, including redness, itching, swelling, and the formation of blisters.
7. Memory response: The immune response generates memory T cells, which provide long-term immunity. If the person is re-exposed to urushiol in the future, the memory T cells recognize it more quickly, leading to a faster and more robust immune response.
In summary, contact dermatitis due to poison ivy is mediated by an immune response called allergic contact hypersensitivity. This involves the binding of urushiol to skin proteins, antigen presentation, activation of T cells, release of cytokines, inflammation, and the generation of memory T cells for future protection.