Migration inhibition of human leukocytes mixed with phytohemagglutinin-preincubated mononuclear leukocytes.

An in vitro test able to demonstrate phytohemagglutinin (PHA)-induced migration inhibition of human peripheral blood leukocytes was investigated. The migration inhibition was demonstrated by the agarose migration technique. Purified mononuclear leukocytes which had been incubated for 30 min with PHA, then washed and added to non-separated leukocytes induced migration inhibition of the mixed cell population. Since no PHA was added to the non-separated leukocytes, a direct PHA effect on polymorph migration was avoided. If the PHA-preincubated mononuclear leukocytes were heated at 56 degrees C for 30 min, their ability to cause migration inhibition was abolished. This suggests that the inhibition was caused by migration inhibitory factor (MIF) produced by the PHA-stimulated lymphocytes.