Early and late reactions in contact sensitivity in the mouse

Several phases of plasma extravasation have been identified during the course of a contact sensitivity challenge reaction in mice. An early reaction at 1 h is seen which may be mast cell mediated. This is followed by the main phase of extravasation at 3-4 h. This phase is not seen in mice sensitized for less than 5 days and is transferable passively by serum. Between 8 and 15 h there is a prolonged period of moderately intense extravasation which represents the delayed hypersensitivity component of the reaction. Beyond 15 h there is virtually no further extravasation.