Dissociation of MIF activity and in vitro lymphocyte transformation in the development of experimental allergic thyroiditis in guinea pigs.

Macrophage migration inhibitory factor (MIF) activity and in vitro lymphocyte transformation to homologous thyroid antigen were compared in cultures of lymph node cells obtained from 123 guinea pigs at weekly intervals after a single injection of homologous thyroid extracts in complete Freund's adjuvant (CFA). MIF activity was not detectable at the early stage of immunization but became manifest 2 and 3 weeks after sensitization and a high level was maintained during 4-7 weeks. On the other hand, lymphocyte transformation preceded the appearance of MIF activity and attained its maximum 2 weeks after sensitization before the establishment of thyroiditis. It is indicated that MIF activity and lymphocyte transformation predominate separately in the course of immunization. There was a considerable correlation between intensity of MIF activity and severity of thyroiditis in individual animals during the advanced stage (4-6 weeks after sensitization) of the disease. Also, a lower but significant correlation was seen between lymphocyte transformation and severity of thyroiditis. However, about half of animals in the advanced stage of thyroiditis failed to exhibit antigen-stimulated lymphocyte transformation, despite a positive MIF activity.