Migration inhibitory effect of cell-free supernatants from PHA-activated cultures of human mononuclear leukocytes.

A two-step test for the demonstration of phytohaemagglutinin (PHA)-induced production of migration inhibitory factor (MIF) was investigated. In the first step, human purified mononuclear leukocytes were activated by incubation with PHA for 1 h. Then the cells were washed thoroughly and cultured for 1 to 4 days in TC medium without PHA. In the second step, the MIF-activity of the cell-free culture supernatants was tested on non-separated human leukocytes. The migration inhibition reaction was demonstrated by the agarose migration technique. The supernatants might have been contaminated by PHA, but it was shown that such contamination would be unable to cause any appreciable migration inhibition of the indicator leukocytes.