Response of hypersensitive mice to the footpad injection of living homologous or heterologous mycobacteria: preliminary report.

Mice sensitized by the injection of viable mycobacteria into one of the hind footpads responded to a second injection of mycobacteria (3 to 4 weeks later), introduced into the contralateral foot, with a degree of footpad swelling that was both accelerated and exaggerated beyond that observed after the first inoculation. The degree of specificity of this reaction (i.e., response to homologous versus heterologous mycobacteria) was comparable to that previously reported for dermal reactions of hypersensitive guinea pigs to tuberculin or tuberculin-like antigens from mycobacteria. In preliminary studies it was impossible to achieve this state of specific sensitization by vaccinating mice subcutaneously with water-in-oil emulsions of heat-killed mycobacteria; reasons for the failure are discussed. It is suggested that this tool could prove useful in both taxonomic and immunological investigations. Advantages and disadvantages of the mouse footpad test in relation to the dermal skin test in guinea pigs are discussed.