The macrophage disappearance reaction (MDR), as an in vivo analogue of in vitro tests for delayed hypersensitivity, was utilized in mice immunized with M. tuberculosis or mouse thyroid extract (MTE). The optimal schedule for the induction of macrophages in peritoneal exudates and the optimal concentration of antigen for the MDR were determined. Macrophage disappearance occurred 4 hr after immunized mice received an intraperitoneal injection of 200 μg of soluble antigen. The MDR was found to be antigen specific. Intraperitoneal injection of an unrelated antigen or tissue culture medium alone did not cause macrophage disappearance; however, the re-injection of the antigen used for immunization caused a 70-80% reduction of macrophages. Macrophage disappearance was greater in mice immunized with M. tuberculosis than in mice immunized with MTE. Comparison of the MDR with the footpad test in these 2 groups showed that mice immunized with M. tuberculosis developed a higher degree of delayed hypersensitivity than the group immunized with MTE. These results demonstrate that the MDR represents a specific and quantitative method for detecting the delayed type of cellular immune response in mice.
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