Soluble factors in tolerance and contact sensitivity to DNFB in mice. X. IL-2 is the activation signal mediating release of synthesized suppressor factor

Two signals are required for the in vitro activation of Lyt2+ T suppressor cells (Ts) from mice tolerized with 2,4-dinitrobenzene sulfonate (DNBS) to produce soluble suppressor factors (SSF) which suppress the transfer of contact sensitivity to dinitrofluorobenzene (DNFB). Recognition of DNP/class I MHC (signal one) stimulates the Ts to synthesize SSF. Release of SSF requires a soluble mediator (signal two) produced by the interaction of L3T4+ T cells from tolerant mice with I-A on metabolically functional cells in the DNP-presenting cell population. The purpose of this study was to examine the nature of this second Ts activation signal. Coculture of tolerant spleen cells and glutaraldehyde-fixed (Glu-) DNP-labeled spleen cells (DNP-SC) resulted in the synthesis but not release of SSF. Addition of either IL-1 or IL-2 to these cultures induced SSF release. Treatment of such cultured cells with the anti-murine IL-2 receptor antibody PC 61.5.3 blocked the IL-2- and IL-1-stimulated release of SSF. Release of SSF was also blocked when tolerant cells were cultured with (unfixed) DNP-SC in the presence of a monoclonal anti-IL-2 antibody. IL-2 but not IL-1 was able to stimulate the Ts to release synthesized SSF in the absence of L3T4+ TH activity. First, addition of IL-2 to cocultures of tolerant cells and DNP-presenting I-A- cells induced release of the synthesized SSF, whereas addition of IL-1 did not. Second, IL-2 also stimulated SSF release in cocultures of L3T4+ T cell-depleted tolerant cells and Glu-DNP-SC, whereas IL-1 did not. Tolerant cells pretreated with IL-2 and then washed were able to synthesize and release SSF upon culture with Glu-DNP-SC. Pretreatment of tolerant cells with IL-1 did not stimulate SSF release upon subsequent culture with Glu-DNP-SC. These results indicate that the Lyt2+ Ts from DNBS-tolerant mice express IL-2 receptors and IL-2 is the lymphokine which induces the Ts to release synthesized SSF. Thus, IL-2 provides a differentiative signal during the functional activation of these regulatory T cells.     

Soluble factors in tolerance and contact sensitivity to 2,4-dinitro-fluorobenzene in mice. IX. A monoclonal T cell suppressor molecule is structurally and serologically related to the alpha/beta T cell receptor

Ts cells from mice tolerized with dinitrobenzene sulfonate produce a DNP-specific, MHC-restricted soluble suppressor factor (SSF) which regulates contact sensitivity to 2,4-dinitro-fluorobenzene. Previous studies have shown that the SSF-producing T cells and the soluble factor have the same hapten/MHC specificity suggesting that SSF may represent a secreted form of the Ts membrane receptor. The relationship between TCR proteins and SSF was investigated by examining the structural and serologic properties of a monoclonal DNP/H-2Kd-specific suppressor molecule produced by a Ts hybridoma. Reduction followed by alkylation abrogated the ability of the 3-10 molecule to inhibit transfer of contact sensitivity to 2,4-dinitro-fluorobenzene, indicating that intact disulfide bonds were a required structural property for suppression. Reduction of the 3-10 molecule followed by affinity chromatography on DNP-coupled Sepharose beads indicated that the 3-10 suppressor molecule is a dimer and that one of its chains binds to cell-free DNP. Serologic properties of the 3-10 molecule were examined by determining the ability of pan-reactive rabbit anti-TCR antibodies and anti-V beta 8 mAb KJ16.133 and F23.1 to adsorb suppressor activity from 3-10 culture supernatant and affinity purified 3-10 ascites material. All three reagents adsorbed the suppressor activity whereas control antibodies had no effect. When 3-10 material was passed through a F23.1-conjugated Sepharose affinity column, suppressor activity was recovered in the column eluate but not in the effluent fraction. When the 3-10 molecule was reduced and separated into its two chains (i.e., DNP-binding and non-DNP-binding chains), it was found that the anti-V beta 8 antibody F23.1-bound to the non-DNP-binding chain of the suppressor molecule. Collectively, these results indicate that the monoclonal 3-10 suppressor molecule is structurally similar to the alpha/beta TCR and suggest that the 3-10 molecule expresses a determinant encoded by the V beta 8 family of TCR genes. These results are consistent with our hypothesis that these suppressor molecules represent a secreted form of the TCR expressed on the surface of the DNP-specific Ts.