Delayed-type hypersensitivity measured as an increase of ear thickness in guinea pigs.

Determination of swelling at an intracutaneous test site in the pinna of the ear of guinea pigs immunized with protein antigens in complete Freund's adjuvant was found to be a more sensitive assay of delayed-type hypersensitivity than the measurement of flank skin erythema and induration. In fact, 100 times less specific antigen was needed to detect 24-hour reactivity in the pinna of the ear. Reactivity early after sensitization (cutaneous basophil hypersensitivity), however, was best revealed as an erythematous lesion of the flank skin 24 h after testing.