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We isolated a unique TCR alpha-chain derived from the OVA-specific Ts hybridoma, 231F1. The TR alpha-chain consists of V alpha 11.3, a unique J alpha and a complete sequence of C alpha region. Transfection of the TCR-alpha cDNA into a TCR-alpha-, TCR-beta+ T cell line, 175.2, resulted in the expression of TCR-alpha beta, and the transfectant contained a 35-kDa peptide having the TCR- alpha-specific antigenic determinant. However, the stable transfectant failed to release a peptide with the TCR-alpha determinant upon stimulation with anti-CD3. In contrast, overexpression of the cDNA in the 231 F1 cells markedly increased the formation of the 55-kDa peptide, which reacted with both anti-glycosylation-inhibiting factor (GIF) and the mAb H28-710. Definitive evidence for the relationship between the 55-kDa peptide and the TCR alpha-chain was obtained by transfection of the cDNA of the TCR alpha-chain with histidine tag into the 231F1 cells. The 55 kDa GIF peptide formed by stable transfectants of the TCR-alpha-tag cDNA bound to Ni+-nitrilotriacetic acid-agarose. Upon stimulation with anti-CD3, a stable transfectant of the TCR-alpha cDNA formed OVA-specific GIF which contained the 55-kDa GIF peptide, and bound not only to anti-TCR-alpha column but also to anti-TCR-beta column. The results indicate that the OVA-specific GIF consists of the TCR-alpha+ 55-kDa GIF and another peptide with TCR-beta determinant. It was found that the association of the TCR-beta+ peptide with the 55-kDa GIF is required for binding of the factor to OVA, but not essential for the formation and release of the latter peptide.

Stimulation of OVA-specific suppressor T cell (Ts) hybridoma and bee venom phospholipase A2 (PLA2)-specific Ts hybridoma with Ag-pulsed APC or by cross-linking of CD3 resulted in the formation of Ag-specific glycosylation-inhibiting factor (GIF). Affinity-purified Ag-specific GIF preparations, obtained by using Ag-coupled Sepharose or anti-TCR alpha-chain-coupled Affi-Gel, contained a 55-kDa peptide, which bound both polyclonal anti-GIF Abs and anti-TCR-alpha mAb in immunoblotting. The same hybridomas constitutively secrete 13-kDa bioactive GIF peptide that has no affinity for homologous Ag, but neither the Ag-specific GIF activity nor 55-kDa GIF peptide was detectable in culture supernatants of unstimulated cells. Northern blot analysis of mRNA from the anti-CD3-stimulated hybridoma with 32P-labeled GIF cDNA revealed only 0.6 kb mRNA, which encodes the 13-kDa nonspecific GIF. No mRNA of the 55-kDa GIF was detectable. A representative OVA-specific Th hybridoma, DO 11.10 cells contain the 0.6 kb GIF mRNA and constitutively secrete inactive GIF peptide. However, the Th hybridoma failed to secrete the 55-kDa peptide or any peptide with the TCR-alpha determinant upon stimulation with anti-CD3. It appears that the formation of the 55-kDa peptide with the TCR-alpha determinant is unique for a subset of T cells including Ts cells that form bioactive GIF.

Ovalbumin-specific, H-2Kd restricted, CD8+ Ts cells of clone 17.2 were shown to produce an OVA-specific Ts cell factor (TsF17.2) possessing the same Ag specificity and MHC restriction as those of the intact Ts cells. The Ts cell clone was generated from a single cell of the spleen of a mouse which had been immunosuppressed by injection of tolerogenic OVA(mPEG)12 conjugate. For the elucidation of the nature of TsF17.2, it was characterized by serologic, physicochemical, and Western blot analyses. It was found that 1) the OVA-specific suppression of in vitro antibody production by TsF17.2 could be blocked by mAb H28-710 which binds to an epitope of the constant region of the alpha-chain of TCR; 2) the TsF17.2 could be sequestered by, and eluted from, immunosorbents prepared by coupling to Affi-Gel Hz the H28-710 mAb or the mAb H57-597 and F23.1 which are specific, respectively, for an epitope of the constant region of the beta-chain and an epitope of the V beta 8 region of the TCR; and 3) the TsF17.2 had a pl of 7.0, m.w. of 84,000, and consisted of two disulfide-linked subunits of 42,000 each. After electroelution from the SDS-PAGE gel, the m.w. 84,000 molecule retained its capacity to suppress in vitro antibody production in an OVA-specific manner. From all these results it was concluded that this Ts cell factor may represent a soluble form of the alpha beta heterodimer of TCR of cloned Ts cells.

We report a new suppressor function of CD8+ CD57+ lymphocytes from HIV-seropositive patients recipients, on the cytolytic activity of allospecific CTL, NK and LAK cells. This inhibitory effect is mediated by a non-antigen specific soluble factor distinct from PGE2, TGF beta and TNF alpha and beta. Biochemical characterization indicates that the CD8+ CD57+ inhibitory activity: 1) is heat and trypsin resistant but remains sensitive to pronase E hydrolyse, 2) specifically bind to concanavalin A-sepharose column, 3) is mediated by a 20-30 kdaltons glycoprotein.