PARTIAL-PURIFICATION AND CHARACTERIZATION OF CHICKEN INTERLEUKIN-2

Chicken interleukin 2 (IL-2) activity was partially purified from conditioned medium produced by culturing chicken splenic lymphocytes in the presence of concanavalin A. The purification procedure included sequential steps of gel filtration chromatography, reverse-phase high-pressure liquid chromatography, and phenyl-sepharose chromatography. Two peaks of IL-2 activity with apparent mol. wt. ranges of 36-39 kD and 17.5-25 kD were eluted from the Sephadex G100 gel filtration column. An increase in IL-2 spec. act. from 14 U mg-1 to between 2000 and 20 000 U mg-1 was obtained for the Sephadex G100 column peaks when subjected to the subsequent steps of the purification procedure. Alkylative reduction of the higher mol. wt. Sephadex G100 column peak (followed by re-chromatography with Sephadex G100), resulted in generation of the lower ( 17.5 kD) mol. wt. peak, indicating that chicken IL-2 is capable of either dimerizing or forming aggregates with other proteins. Elution of the lower mol. wt. IL-2 activity from a non-reducing sodium dodecyl sulfate-polyacrylamide gel demonstrated an apparent mol. wt. for chicken IL-2 of 20 kD, which confirmed the range of 17.5-25 kD seen with gel filtration.