Characterization of IgG-containing DEAE fractions of canine serum

A high-titered canine antilymphocyte serum was chromatographed on DE-52 cellulose and the fractions were assayed for cytotoxic activity. Although cytotoxicity was associated with the first 63% of the column effluent corresponding to fractions 1 through 7, significant activity (256) was demonstrable only in fractions 2, 3, 4, and 5. An immunoelectrophoretic study of fractions 1 through 5 showed only IgGa in fraction 1, IgGa and IgGb as electrophoretically separate arcs in fraction 2, and as electrophoretically inseparable arcs in fractions 3 through 5. Cytotoxicity is postulated to be associated with the IgGb subclass, since titers correspond with the distribution of IgGb in column fractions.