The effect of tunicamycin on the molecular heterogeneity of guinea pig migration inhibitory factor

Abstract

Migration inhibitory factor (MIF) was produced by guinea pig lymph node cells stimulated with concanavalin A in the absence and presence of the glycosylation inhibitor tunicamycin. The active supernatants were purified on Sephadex G-100 and fractionated into pH 3-MIF and pH 5-MIF using isoelectrofocusing. When produced in the absence of tunicamycin pH 3-MIF shows extensive charge heterogeneity with activity focusing from pH 3.0 to 4.5; it elutes from Sephadex G-75 with molecules of an apparent MW of 70,000. In contrast, pH 3-MIF produced in the presence of tunicamycin (TM-pH 3-MIF) focuses as a sharp homogeneous peak with a p I of 3.6 to 4.0 and elutes from Sephadex G-75 with molecules of an apparent MW of 25,000–35,000. TM-pH 3-MIF is trypsin sensitive and displays a buoyant density similar to that of proteins which contain little or no carbohydrate ( ϱ 25 1.26−1.34). Tunicamycin caused no detectable change in the characteristics of pH 5-MIF. This study indicates that lymphocytes stimulated in the presence of tunicamycin produce a novel species of pH 3-MIF with characteristics distinct from classical pH 3-MIF.