Migration of monocytic-phagocytic cells from guinea pigs immunized with complete Freund's adjuvant is regularly and specifically inhibited in tissue culture by 5 to 10µg/ml of PPD. Migration of leukocytes and spindle cells from such animals is inhibited by PPD less consistently and to a lesser degree.
Cutaneous hypersensitivity to PPD in these animals develops 5 days after adjuvant immunization; at this time migration of mononuclear cells from explants of lung and regional node is inhibited by addition of 10 µg/ml of PPD. Splenic cells become sensitive 2 to 3 weeks after immunization and hepatic macrophages become sensitive only several weeks later.
Cellular hypersensitivity to antigen, as measured by this technique, develops in guinea pigs infected with Histoplasma or immunized with emulsions of complete Freund's adjuvant and T4 bacteriophage, bovine γ-globulin, human γ-globulin, or picrylated guinea pig skin. The sensitivity is specific for the immunizing antigen.
Serum from immunized guinea pigs increases the inhibitory effect of antigen on the migration of cells from sensitive tissue and confers antigenspecific sensitivity on normal cells. The serum factor affects primarily leukocytes.
The significance of in vitro hypersensitivity of several cell functions to antigen is discussed in regard to the cell types which have been available in culture.