Mitogenic factor as an in vitro correlate of delayed hypersensitivity in the guinea pig.

The relationship of mitogenic factor (MF) to delayed hypersensitivity was examined in the guinea pig. MF was readily produced in vitro by blood leucocytes from animals sensitized with Keyhole limpet haemocyanin in Freund's complete adjuvant. Such animals exhibited delayed skin reactions and macrophage migration inhibition. Treatment with cyclophosphamide markedly reduced serum antibody but caused no diminution of MF or delayed skin reactions. A migration inhibition response was observed 10, but not 20, days after sensitization by means of incomplete adjuvant.