The biochemical study of rat T-cell growth factor (interleukin 2)

T-cell growth factor (interleukin 2) was partially purified from the conditioned medium from Con A-stimulated rat splenocytes. It had the molecular weight of 23,000 according to gel filtration and in the range of 17,000-18,000 daltons according to PAGE in the presence of SDS. The molecular forms of IL 2 exhibited isoelectric points (pI) of 5.4-5.8 (major peak), 4.3-4.5 and 6.5-6.8 (minor peaks). T-cell growth-promoting activity was remarkably stable to temperature, pH, SDS and 2-ME treatments. Rat IL 2 did not bind to immobilized Con A, WGA, RC 1, and fucose-binding protein. The conditioned medium also contained the inhibitor of IL 2-dependent T-cell proliferation.