A simple rapid method for detection of IL-2 in a physiological medium.

The Con A-activated proliferation of C57BL/6 mice thymus cell suspension is completely blocked by a low concentration of hydrocortisone. This inhibition is reversed by the addition of a 24 h Con A-activated splenic cell supernatant to the thymic cell culture. The restoring activity is completely destroyed by heating. Restoration is not obtained by addition of IL-1-rich supernatant from an LPS-activated peritoneal adherent cell population. The supernatant of a 24 h splenic cell culture activated by Con A in the presence of indomethacin not only restores hydrocortisone-blocked thymocyte reactivity but also enhances thymic cell stimulation. Addition of PGE to the splenic cell culture inhibits the restoring potency of the supernatant. These results are in accord with the proposition that IL-2 is responsible for the restoring phenomenon. These properties have been used to develop a semi-quantitative method for detection of IL-2 in a physiological medium.