Using gel filtration and preparative isotachophoresis, the migration inhibitory factor (MIF) was highly purified from human lymphocytes activated with concanavalin A. MIF is an acidic protein with a mol wt of approximately equal to 25,000 daltons as determined by gel filtration and analytical polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The protein inhibits migration of macrophages in the capillary test and in addition, has a slowing effect on the electrophoretic mobility of guinea pig peritoneal macrophages. Rabbit antibodies specific for this protein, as determined by immunochemical techniques, neutralized the biological effect of MIF on migration and on the electrophoretic mobility of macrophages.

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