ROLE OF IL-4 IN DELAYED-TYPE HYPERSENSITIVITY

IL-4 plays a key role in the contact sensitivity skin reaction. This h as several implications. First, the view that contact sensitivity (CS) is only mediated by cells with a Th1 profile of cytokine secretion ne eds modification, in the light of the essential role of IL-4 at the ef fector stage. Second, the concept of a single cell involved in the sys temic transfer of CS is no longer tenable, as it is known that both al pha:beta and gamma delta cells are required. Studies with the cell lin es (which contain both alpha beta and a few gamma delta cells) suggest that this double requirement may involve the action of IL-4 on gamma delta cells, which bear receptors for IL-4. Finally, the view that T c ell lines only transfer CS when injected locally, but not when injecte d intravenously (systemic transfer), is correct but incomplete, as T c ell lines actually give systemic transfer of CS, providing the cell li ne or the recipient is treated with IL-4.