Cell-mediated and humoral immune responses in mice. I. Necessary conditions for the detection of delayed-type hypersensitivity.

Footpad assay of delayed-type hypersensitivity to bovine serum albumin (BSA) was studied. Injection of saline solution of BSA (S-BSA) into footpads of sensitized mice resulted in the development of only the local Arthus-type reaction. Injection of alumprecipitated BSA (AP-BSA), however, was effective in generating both Arthus- and delayed-type reactions. The difference between S-BSA and AP-BSA in the ability of elicitation of delayed-type reaction may be attributable to the difference in the retention of these two forms of antigen in the footpad, since S-BSA was found to be eliminated much more rapidly from footpads than AP-BSA.