What type of immune response can be seen in reactions like contact dermatitis?

The immune response observed in conditions such as contact dermatitis is characterized as cell-mediated immunity. This response primarily involves T lymphocytes (T cells) rather than antibodies, which are more associated with humoral immunity.

In contact dermatitis, upon initial exposure to an allergen, such as poison ivy, the skin sensitizes the immune system. Subsequent exposure induces an immune response that is mediated by T cells, particularly CD4+ helper T cells and CD8+ cytotoxic T cells. These cells recognize the allergen presented by antigen-presenting cells and initiate a localized inflammatory response, resulting in symptoms like redness, swelling, and itching.

Cell-mediated immunity plays a crucial role in the defense against intracellular pathogens, as well as in the response to allergens, and is distinct from humoral immunity, which focuses on antibody production. This specificity of T cell activation and the consequent inflammation are what define contact dermatitis and similar type IV hypersensitivity reactions.