Soluble interleukin 2 receptors are released by long term-cultured insulin-specific T cells transiently after contact with antigen.

An enzyme-linked immunosorbent assay was used to quantitate soluble interleukin 2 receptors (IL 2R) released by antigen-dependent, insulin-specific murine T cells into the culture supernatant, as well as cell-associated IL 2R present in cell lysates. IL 2R were released solely after T cell activation by antigen. The release of IL 2R was transient, reaching optimal levels within 72 hr after antigen challenge and gradually declining to background levels thereafter, when the cells were subcultured in IL 2-enriched medium. The decrease in the amount of IL 2R released during culture in IL 2-containing medium paralleled the decrement in cellular IL 2R detected in cell lysates, in cell surface-expressed IL 2R as determined by cytofluorometry, as well as in high-affinity IL 2R. In contrast, IL 2R were constitutively released by an IL 2-dependent T cell clone. Soluble IL 2R might exert an immunoregulatory function by competing with cellular IL 2R for IL 2 binding.