Evans blue dye adjuvant enhances delayed hypersensitivity while blocking immunity to Mycobacterium tuberculosis in mice

Evans blue dye functions as an adjuvant with protein antigens in saline to induce cell-mediated immunological responses in mice. But when used to help induce cell-mediated tuberculoimmunity, it decreased mouse resistance to tuberculosis instead of helping induce immunity. This paradox was investigated. As could be expected from previous work with other antigens, the dye did promote induction of delayed hypersensitivity in mice to tuberculoprotein when injected in saline with killed tubercle bacilli. Peritoneal macrophages from mice injected with the dye responded normally to migration inhibition factor. Morphologically, these cells were moderately "activated" compared with similar cells taken from untreated mice. However, such cells incubated with tuberculosis growth inhibition lymphokine in an in vitro test for tuberculoimmunity did not express tuberculoimmunity, whereas macrophages from untreated mice did. Therefore, Evans blue dye did promote induction of cell-mediated immunological responses and tuberculoimmunity in lymphocytes, but under the conditions used in these experiments, it also blocked expression of tuberculoimmunity by macrophages.