Biochemical characterization and separation of low molecular weight urinary thymocyte and fibroblast proliferative activities.

Normal human urine was found to contain two low molecular weight (ca. 4000 and 2000 molecular weight [mw]) fractions that exhibit IL-1-like properties. In vitro, both the 2K and 4K fractions demonstrated mouse thymocyte proliferative activity in the presence of phytohemagglutinin (PHA) (i.e., LAF-like), whereas only the 2K fraction also induced proliferation of human dermal fibroblasts. A third fraction (ca. 75,000 mw), which demonstrated both biologic activities, was shown to convert exclusively to the 2K and 4K activities after treatment with the nonionic detergent CHAPS (3-[3-cholamidopropyl)-dimethylammino]-1-propane sulfonate). Liquid isoelectric focusing of the 4K urinary LAF fraction revealed that the thymocyte costimulatory activity focused at pH 5.3 and 6.7. The thymocyte proliferative activity in the 2K pool focused at pH 7.5 and 8.7, as well as at pH 5.3 and 6.7. The 2K fibroblast activity, however, focused only at pH 7.5. Anion exchange chromatography also separated the fibroblast and thymocyte comitogenic proliferative activities. The fibroblast activity eluted as two sharp peaks between 0.5 and 0.7 M NaCl, whereas the 2K and 4K thymocyte activities eluted as a broader peak with 1 M NaCl. The origin of the 2K fibroblast proliferation factor remains to be established. However, since the urinary gel filtration fractions with low mw thymocyte costimulatory activity did not support the growth of IL-2-dependent cell lines, they are presumably fragments of IL-1 rather than related to IL-2. Results of this study further suggest that the lymphoproliferative activity and fibroblast proliferative activity of interleukin-1 are not necessarily coupled.