Antigen-dependent MIF was produced in inbred mice. Lymph node cells from mice sensitized to tubercle bacilli were incubated with small quantities of antigen. The supernatant contained antigen-dependent MIF and its activity when tested on mouse and rabbit spleen was minimal unless PPD was added to the supernatant. The production of the antigen-dependent MIF was T cell-dependent, as shown by the use of anti-theta serum. Its molecular weight was in the range of 50--100,000 and it was concluded that the factor is different from conventional antibodies or antigen-antibody complexes
