Delayed‐Type Hypersensitivity in the Mouse

A simple reproducible footpad assay of delayed‐type hypersensitivity (DTH) in CBA, C3H, and Bagg mice to Salmonella adelaide flagellin and its derivatives is described. DTH reactions were of delayed onset (12‐24 hours), long duration (3‐4 days), and characterized histologically by extensive infiltration of the hypodermis and muscle with mononuclear cells. Immediate (0‐3 hours) and late (36‐48 hours) Arthus reactions were also observed in certain instances but did not preclude detection of the 24‐hour DTH reaction. Maximal DTH reactivity was induced by microgram doses of monomeric (MON) or polymerized (POL) flagellin in saline, 2‐8 days after primary challenge. POL elicited greater DTH reactions than MON, presumably because of its larger size.