INDUCTION OF IL-2 RECEPTOR EXPRESSION AND PROLIFERATION OF T-CELL CLONES BY A NOVEL CYTOKINE(S)

We found a unique T cell IL-2 receptor (IL-2R)3 3 Abbreviations used: SN, supernatant; APC, antigen presenting cells; IL-2RIF, IL-2 receptor-inducing factor; Ab, antibody; OVA, ovalbumin; IL-2R, IL-2 receptor; rADF, recombinant ATL-derived factor; TCR, T cell receptor.-inducing activity in the supernatant (SN) of the TH1 clone stimulated with antigen on spleen cells as antigen-presenting cells (APC). We have tentatively named this activity the IL-2R-inducing factor (IL-2RIF) and have characterized the activity. The SN induced IL-2R and proliferation of TH1 clones stimulated with B cell APC, which could not induce IL-2R in the absence of the SN. Other known cytokines were examined for a IL-2RIF activity; however, none of cytokines examined exerted a similar activity. Moreover, the neutralizing antibodies against the known cytokines tested did not block the IL-2RIF activity in the SN. When TH1 clones were stimulated with immobilized anti-CD3 or with fixed B cell APC in the presence of partially purified IL-2RIF, these clones expressed IL-2R and showed IL-2-dependent proliferation, whereas they induced neither IL-2R expression nor proliferation in the absence of IL-2RIF activity. These observations suggest that IL-2RIF activity is mediated by a novel cytokine(s) and the cytokine plays an important role as a second signal in the activation of the TH1 clone. © 1992.