Abstract
Swine interleukin 2 (IL-2) activity was assayed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) colorimetric assay using murine IL-2 dependent cell line (CTLL-2). The culture supernatant of mesenteric lymph node (MLN) cells stimulated with phytohemagglutinin-P (PHA) induced a generation of MTT formazan in a dose-dependent manner, suggesting dose-dependent proliferation of CTLL-2. The maximal swine IL-2 activity was observed in the culture of MLN cells at 1 to 2×107 cells/ml when stimulated with 20 to 40 μg/ml PHA for 48 hr. Based on these findings, a large culture of MLN cells to prepare swine IL-2 were performed under the following condition; cell concentration of 1×107 cells/ml, PHA concentration of 20 μg/ml, a culture scale of 200. to 400 ml, and a stirring speed of 30 rpm. Swine IL-2 activity was detected from 4 hr after PHA stimulation, and rapidly increased until 16 hr. Almost maximal IL-2 activity in stirring culture was observed at the incubation of 20 hr. Swine IL-2 was partially purified by Sephacryl S-200 gel filtration and the estimated molecular weight was about 32 kD based on the peak of IL-2 activity. The pI value of swine IL-2 was estimated to be approximately pH 5.3. Swine IL-2 was sensitive to acid (pH 3.2) or alkaline (pH 10.5), 4 or 8 M urea, trypsin, and the heating at 70°C. These physico-chemical properties of swine IL-2 was similar to those of human, murine or feline IL-2.
