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

Area of Science:

• Immunology
• Microbiology

Background:

• Evans blue dye is an adjuvant that typically enhances cell-mediated immunological responses.
• Its role in inducing tuberculoimmunity has yielded paradoxical results, decreasing rather than increasing resistance to tuberculosis.

Purpose of the Study:

• To investigate the paradoxical effect of Evans blue dye on cell-mediated tuberculoimmunity in mice.
• To elucidate the mechanisms behind the dye's conflicting influence on immune responses.

Main Methods:

• Mice were injected with Evans blue dye and killed tubercle bacilli to assess delayed hypersensitivity.
• Peritoneal macrophages were analyzed for response to migration inhibition factor and in vitro tuberculoimmunity assays.
• Macrophage activation and lymphokine function were evaluated.

Main Results:

• Evans blue dye promoted delayed hypersensitivity and moderate macrophage activation.
• Macrophages from dye-injected mice did not express tuberculoimmunity in vitro, despite normal response to migration inhibition factor.
• Lymphocytes showed induced cell-mediated immunological responses and tuberculoimmunity.

Conclusions:

• Evans blue dye can induce cell-mediated immunological responses and tuberculoimmunity in lymphocytes.
• However, the dye also inhibits the expression of tuberculoimmunity by macrophages under specific experimental conditions.
• This dual effect explains the observed paradox in mouse resistance to tuberculosis.