Migration inhibitory factor and type II interferon in the circulation of mice sensitized with mycobacterial components.

Migration inhibitory factor (MIF) and type II interferon were released into the circulation after mice had been sensitized i.v. with a bacillus of Calmette and Guerin (BCG) cell-wall-in-oil vaccine and then challenged four weeks later with 50 mg old tuberculin. At least two components of BCG, protein (PPD) and lipid (P-3), have been identified which are essential for the type of sensitization in which mediators are released after appropriate challenge. The route of sensitization had a marked effect on the development of delayed footpad reactions, release of lymphokines, and resistance to infection with virulent tubercle bacilli. Sensitization by the subcutaneous route tended to induce more pronounced delayed footpad reactions, whereas the i.v. route of sensitization was associated with maximum release of mediators. A close correlation existed between the conditions of sensitization that resulted in maximum production of lymphokines (MIF and Type II interferon) and those that caused protection against aerosol challenge with a virulent strain of Mycobacterium tuberculosis.