Induction in the guinea pig of delayed hypersensitivity to compound 48/80

Intradermal injection of compound 48/80 into the nuchal area of the guinea pig in an adjuvant/water emulsion induced strong delayed hypersensitivity. Groups of 8 animals were injected weekly for 3 weeks with 100 microliter of 10%, 1%, 0.1% or 0% of compound 48/80 in the adjuvant/water emulsion. 6 of 8 animals in the highest concentration group died between 1 and 24 h after the first injection. The other concentrations produced no visible evidence of acute toxicity. 2 weeks after the last injection, the animals were challenged with an open topical application of 1%, 0.1%, 0.01%, and 0% of compound 48/80 in 3:7 propylene glycol/ethanol. The strongest reactions were found in the 0.1% induction group. Some degree of immunologic tolerance may have occurred in the 1% induction group resulting in somewhat weaker challenge responses.