Which disease is associated with Type IV allergic responses where T-lymphocytes are involved?

Type IV allergic responses, also known as delayed-type hypersensitivity, are primarily mediated by T-lymphocytes rather than antibodies. This type of immune response does not occur as quickly as other allergic reactions, such as those mediated by IgE antibodies, which are responsible for immediate hypersensitivity reactions like hay fever or asthma.

Contact dermatitis is a classic example of a Type IV hypersensitivity reaction. It occurs when the skin comes into contact with certain allergens (like poison ivy, nickel, or various chemicals) that trigger an immune response mediated by T-cells. Upon re-exposure to the allergen, sensitized T-lymphocytes generate an inflammatory response that causes symptoms such as redness, itching, and swelling.

In contrast, hay fever and food allergies involve immediate hypersensitivity reactions mediated by IgE antibodies, leading to quicker symptoms upon exposure. Asthma can also be related to IgE-mediated reactions, particularly in allergic asthma cases. Therefore, the association of T-lymphocytes and delayed hypersensitivity with contact dermatitis makes it the correct answer in this context.