[Isolation of immunoglobulin G-binding factor from blood lymphocytes of cows with lymphocytic leukemia].

Incubation of bovine blood lymphocytes in the medium without serum at 37 degrees C caused the spontaneous release of immunoglobulin G-binding factor (IBF-IgG), which was isolated from the medium by the affinity chromatography on IgG, immobilized on sepharose 4B. The electrophoretic analysis showed one polypeptide chain with a molecular weight of 72000 Dalton. The biological activity of IBF-IgG was tested using the EA-rosette inhibition technique. The antibodies, obtained against IBF-IgG, inhibited both the binding of fluoresceinizotiocianate-labeled IgG to lymphocytes and the EA-rosette formation.