Purification and analysis of an antigen-specific suppressor factor from a T cell hybridoma specific for phenyltrimethylamino hapten

The synthetic monovalent antigen L-tyrosine-p-azophenyltri-methylammonium (tyr (TMA)) induces in A/J mice, a cascade of regulatory T cells in the absence of any detectable effector function (e.g., CTL, delayed-type hypersensitivity, etc.). An important component of the activated T cells is a first order suppressor T cell or Ts1 that is Ly-1+2-, functions only at the afferent limb of the anti-TMA response, binds the TMA ligand and bears cross-reactive idiotypes associated with anti-TMA antibodies. This Ts1 produces a suppressor factor (TsF1) that binds the TMA ligand, bears the cross-reactive idiotypes and I-J determinants and functions to induce an idiotype-specific Ts2 population. To study the biochemistry of this TsF, use was made of T cell hybridomas that constitutively produce TMA-TsF1 (8A.1 and 8A.3). The TsF1 was purified from culture supernatant or cell extracts by (NH4)2SO4 precipitation, reverse phase HPLC and either affinity chromatography or by preparative IEF. The TsF1 has an isoelectric point of 6.5 and a m.w. of 26,000 or 62,000 as analyzed by SDS-PAGE or high performance molecular sieve chromatography. Its precipitation in 30 to 40% (NH4)2SO4; elution pattern from reverse phase high performance columns; its capacity to bind to a mAb specific for L-glutamic acid 60L-alanine30-L-tyrosine10 (GAT)-TsF1 strongly suggest that this protein belongs to the same family of proteins as do the GAT-TsF1 described previously. Most noteworthy is that although these TsF1 proteins show remarkable similarities, they are absolutely specific in their biologic activity; TMA-TsF1 will not suppress the response to GAT-BA-TNP and GAT-TsF1 will not suppress the response to TMA-BA-TNP. Thus the TMA-TsF1 represents a second example of a unique group of Ag-specific proteins whose function is to induce or activate other suppressor T cells in the primary immune response to Ag.