Final answer:
Poison ivy affects the immune system causing a type IV hypersensitivity reaction known as contact dermatitis, involving memory helper T cells and an inflammatory response.
Step-by-step explanation:
Poison ivy has an effect on gardeners and agricultural workers through the immune system. When a person comes into contact with poison ivy, the plant's sap contains urushiol, which is a hapten that can cause an allergic reaction known as contact dermatitis, a type IV hypersensitivity reaction. Initial exposure to poison ivy doesn't typically cause a reaction, but it leads to sensitization. Sensitized individuals have memory helper T cells that can respond to future exposures with an inflammatory reaction. Secondary exposure causes these memory helper T cells to reactivate, releasing inflammatory cytokines that recruit macrophages and cytotoxic T cells, leading to tissue damage at the site of contact.