Interferon induced in human leukocytes by mitogens: production, partial purification and characterization

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Abstract
Interferon was induced in leukocyte suspensions from human buffy coats by exposure to phytohemagglutinin P, concanavalin A (Con A) and staphylococcal enterotoxin A, under a variety of cell culture conditions. Con A was found to rapidly (within 12 h) induce high yields of antiviral activity (1.5 units/1000 cells). Lesser yields were obtained with the other two mitogens studied. The interferon was partially purified to a spec. act. around 105.3 units/mg protein, by batch adsorption on controlled-pore glass (CPG) beads and desorption by ethylene glycol. This material was characterized as containing mainly γ-type interferon. Specifically on gel filtration, a fraction of 45 000 daltons was obtained which could account for virtually all antiviral activity present in the starting material. Furthermore, the ethylene glycol-eluted antiviral activity was acid-labile, serologically distinct from a and β-type interferon and strictly species-specific (no activity detectable on any of the available cell species sensitive to α and β-type interferon). The crude culture supernatant also contained some antiviral activity which resembled β-type interferon in that it adsorbed to CPG, could be desorbed by pH 2 buffer, was acid-resistant and could be neutralized by a specific anti-fibroblast interferon antiserum. The CPG/ethylene glycol-purified γ-type interferon preparation was found to inhibit the growth of certain lymphoblastoid cells (Daudi and Molt-4). It also potentiated natural killer activity of fresh donor lymphocytes. In both respects, the γ-type interferon preparation was not significantly more active than preparations of a and β-interferon of similar antiviral potency.