Functional equivalence of cryptococcal and haptene-specific T suppressor factor (TsF). I. Picryl and oxazolone-specific TsF, which inhibit transfer of contact sensitivity, also inhibit phagocytosis by a subset of macrophages.

Monoclonal and conventional cryptococcal-specific T suppressor factors (TsF) (also called TsFmp) depress phagocytosis by a subset of macrophages, while picryl- and oxazolone-specific TsF depress the passive transfer of contact sensitivity. This paper shows that these haptene-specific TsF also inhibit phagocytosis by a subset of macrophages and, using this assay, that the anti-haptene TsF resemble the anti-cryptococcal TsF in five respects: (i) the need for reexposure to specific antigen to trigger the release of TsF; (ii) genetic restriction in action; (iii) possession of an antigen-binding site; (iv) expression of I-J determinants; and (v) inactivation by reduction and alkylation. Purification of the anti-picryl TsF by sequential affinity chromatography indicates that the inhibition of phagocytosis is due to the TsF itself and not to a TsF-antigen complex. The TsF inhibits phagocytosis by a direct action as macrophages treated with TsF and exposed to antigen do not release a second factor which inhibits phagocytosis. These results and those of the accompanying paper indicate that the anti-cryptococcal and anti-haptene TsF are functionally equivalent, antigen-specific suppressor factors.     

Nonspecific inhibitor of contact sensitivity made by T-acceptor cells: triggering of T cells armed with antigen-specific T-suppressor factor (TsF) requires both occupancy of the major histocompatibility complex recognition site by soluble I-J product and cross-linking of the antigen recognition sites of the TsF

The phenomenon of associative recognition, i.e., the recognition of antigen together with major histocompatibility complex products (MHC) was studied in a model system. T-acceptor cells armed with antigen-specific T-suppressor factor (TsF) released a nonspecific inhibitor of the transfer of contact sensitivity when exposed to antigen together with MHC. The MHC product occurred in a KCl extract of cells and behaved genetically and serologically as I-J. Cells armed with anti-picryl or anti-"oxazolone" TsF could be triggered by the corresponding "bis-picryl-L-lysine" and "bis-oxazolone-L-lysine" together with MHC. This suggested that cross-linking of antigen recognition sites on separate molecules of TsF might be required. To investigate this possibility the bifunctional "mixed" hapten "N alpha-picryl-N epsilon-oxazolone-L-lysine," which is univalent with respect to the picryl and oxazolone haptenic groups, was synthesized. This triggered cells armed with a mixture of anti-picryl and anti-oxazolone TsF but not cells armed with either TsF alone. It was concluded that both occupancy of the I-J recognition site and the cross-linking of separate molecules of TsF was required for triggering. Moreover the hapten and the KCl extract could be given sequentially and in either order. This finding suggested that the triggering of the release of nonspecific inhibitor was due to the separate recognition of I-J and antigen and not to new antigenic determinants produced by their interaction.     

Nonspecific T suppressor factor (nsTsF) cascade in contact sensitivity: nsTsF-1 causes an Ly-1+2- I-A+ immune T cell to produce a second, genetically restricted, nsTsF-2

We studied the mode of action of the nonspecific T suppressor factor (nsTsF-1) made in the picryl (TNP) system when T acceptor cells armed with antigen-specific TsF are triggered by antigen in the context of I-J. This suppressor factor does not inhibit the passive transfer of contact sensitivity directly, as shown by its failure to inhibit passive transfer by immune cells deprived of I-A+ cells. Its immediate target is an immune, antigen-specific, Ly-1+2-, I-A+ T cell. This cell, which may be regarded as a T suppressor effector cell (Ts-eff-2), produces nsTsF-2 when exposed sequentially to nsTsF-1 and antigen. This nsTsF subsequently inhibits the passive transfer of contact sensitivity. The action of nsTsF-2 is MHC genetically restricted. As the nsTsF-2 bears I-A determinant(s), this raises the possibility that it may act by combining with the recognition site for I-A on the T cell that mediates contact sensitivity.     

Mechanism of action of a T suppressor factor (TsF) in contact sensitivity: the T cell target for TsF activity in adoptive transfer of immunity is not effector cell

The passive transfer of contact sensitivity (CS) by immune cells into normal animals requires the interaction of two distinct Ly-1+ T cells, one which is Vicia villosa lectin (VV)-nonadherent, the other which adheres to VV. Functional deletion of either cell type abrogates the adoptive transfer of CS into normal animals, whereas VV-nonadherent cells alone can transfer CS into animals pretreated with cyclophosphamide (Cy). An antigen-specific T suppressor factor, designated TNP-TsF, inhibits the transfer of CS into normal adoptive recipients. TNP-TsF mediates its suppressive activity by inducing an I-J+ subfactor (designated I-J2) from the assay population by the interaction of PC1-F (a TNP-binding subfactor of TNP-TsF) with antigen-primed Ly-2+ T cells. This I-J+ subfactor then complements TNBS-F (an antigen-nonbinding subfactor of TNP-TsF) to form an antigen-nonspecific effector molecule which suppresses DTH responses in an antigen-nonspecific fashion. We report here that TNP-TsF suppresses the adoptive transfer of CS into normal animals but not into animals pretreated with Cy. TNBS-F + I-J2, the effector complex of TNP-TsF, also suppresses the transfer of CS into normal but not Cy-treated animals. When the Ly-1 immune cells were separated into VV-adherent and -nonadherent populations, the TNBS-F + I-J2 suppressor complex suppressed the functional activity of the VV-adherent cell population, but not the VV-nonadherent cells. This suppressive activity correlates with the need for VV-adherent cells in the transfer of CS into normal but not Cy-treated recipients. When an I-J+ molecule (I-J1) from an SRBC-specific TsF was used in place of I-J2 to form a suppressor complex with TNBS-F, this TNBS-F + I-J1 TsF suppressed the transfer of CS into both normal and Cy-treated recipients. This difference in functional suppressive activity correlated with a difference in target cell specificity: TNBS-F + I-J1 suppressed the VV-nonadherent TDTH cell, whereas TNBS-F + I-J2 suppressed the VV-adherent T cell of CS. Immune cells which are transferred under conditions which do not require the VV-adherent cell for transfer are not suppressed by TNBS-F + I-J2 or TNP-TsF, but are suppressed by the TNBS-F + I-J1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of hapten-specific T suppressor factors: genetic restriction of TsF1 activity analyzed with synthetic hybrid suppressor molecules

We have analyzed the first-order suppressor factor secreted by an azobenzenearsonate (ABA)-specific T suppressor cell (Ts) hybridoma. Treatment of the factor with 5 mM dithiothreitol (DTT) yields two fragments with distinct phenotypes and functional capabilities. One fragment is bound by a monoclonal anti-I-J antibody, the other is not. Further, although neither molecular fragment by itself is sufficient to suppress an ABA response, a mixture of the two reconstitutes the suppressive activity. The I-J- portion of the first-order suppressor factor (TsF1) presumably guides the antigen specificity; activity of the ABA-specific Ts I-J- TsF1 factor can be reconstituted with an I-J+ subunit of a TsF molecule of either sheep red blood cell (SRBC) or ABA specificity. The genetic restriction for Igh-linked determinants of the ABA/SRBC hybrid TsF molecules is influenced by the I-J+ portion, regardless of the original antigen specificity of that molecule. The data support a two-subunit TsF model. Polyclonal ABA-specific TsF1 molecules appear to resemble the monoclonal factor in structure.     

A genetically restricted suppressor factor that requires interaction with two distinct targets

We have previously described a genetically restricted suppressor factor (TsF3) that suppresses the terminal phases of the contact sensitivity response. The activity of TsF3 is restricted by genes in the H-2 (I-J) and Igh complexes. This report analyzes the mechanisms responsible for these genetic restrictions. One cellular target of TsF3 is an I-J-bearing antigen-presenting cell population that is sensitive to low doses of cyclophosphamide. To elicit suppression I-J homology is required between this antigen-presenting cell population and the TsF3 donor. In contrast, the Igh-linked genetic restriction exists between TsF3 and an unprimed cell population present in the recipient. These findings suggest that under these experimental conditions TsF3 acts by bridging the APC with cells of the host. Finally, we demonstrated that nonspecific bystander or cognate suppression can be mediated by TsF3, provided specific antigen is present in the site of the ongoing T cell response.     

Murine interstitial nephritis. VII. Suppression of renal injury after treatment with soluble suppressor factor TsF1

We prepared soluble suppressor T cell factor (TsF1) from donor spleens harvested from mice primed with tubular antigen-derivatized lymphocytes to analyze both its functional interactions with a larger suppressor T cell network and its influence on the nephritogenic effector T cell response producing interstitial nephritis to a parenchymal antigen. Our findings indicate that TsF1 is antigen-specific, genetically restricted by I-J in its direct mediation of suppression, and capable of inhibiting the development of interstitial lesions. TsF1 also provides an inducing signal for the activation of effector Ts-2 suppressors following presentation by accessory cells. The induction of a Ts-2 effect, however, requires that the factor-presenting cell and the recipient of such cells share homology at I-J, and that the TsF1, the precursor Ts-2 cells, and the recipient of the Ts-2 effect share the same Igh-V allotype. Finally, the results of this current report clearly demonstrate a possible therapeutic role for soluble suppressor factors in the management of interstitial renal disease.     

TMA-specific first-order T-suppressor hybridoma. I. Characterization of the hybridoma-derived single-chain inducer suppressor factor, TsF1

Experiments described in this report will characterize a monoclonal phenyltrimethylammonium (TMA) specific, first-order T-suppressor factor (TsF1) produced by a T-cell hybridoma, 8A.3. The hybridoma expressed the Thy-1, Lyt-1, Lyt-2 antigens as well as cross-reactive idiotypic (CRI) determinants but did not express I-J encoded epitopes. It was also found to bear determinants recognized by a monoclonal antibody raised against single-chain GAT-specific TsF1. The hybridoma-derived factor was capable of suppressing primary in vitro trinitrophenol (TNP)-specific responses induced with the Brucella abortus antigen, conjugated with TMA and TNP haptens (TMA-BA-TNP). In addition, in vivo administration of 8A.3 culture supernatant resulted in the specific suppression of TMA-specific delayed-type hypersensitivity (DTH) responses. Analysis of this factor revealed it to be an induction-phase, antigen-binding, CRI+, and I-J+ single chain polypeptide. Our results represent only the second such described single chain, antigen binding, I-J+ suppressor factor derived from a monoclonal T-cell hybridoma.     

A primary in vitro antibody assay for antigen-specific T-suppressor factor: cross-suppression of TNP-specific antibody responses by TMA-specific TsF1

We have previously shown that phenyltrimethylammonium (TMA)-specific, first-order suppressor T cells (Ts1) and soluble factors extracted from these cells (TsF1) can suppress delayed-type hypersensitivity (DTH) responses. The TsF1, as monitored in the DTH system, was characterized and found to be a single-chain, antigen-binding, I-J+, and Id+ molecule. To monitor TsF1 in an efficient manner, an in vitro antibody system was developed. The studies show that in vitro stimulation of naive A/J spleen cells with the thymic-independent antigen, Brucella abortus, to which TMA and trinitrophenol (TNP) or fluorescein (FL) are coupled (TMA-BA-TNP or TMA-BA-FL), induces significant numbers of anti-TNP or anti-FL plaque-forming cell (PFC) responses. The addition of TMA-specific TsF1 results in the cross-suppression of 30-50% of the total anti-TNP and FL PFC responses. This activity is antigen (TMA) dependent since suppression occurs only when the TMA ligand is present in the culture media. Analysis of the TNP-specific PFC responses in nonsuppressed cultures revealed that 20-35% of the PFC bear the cross-reactive idiotype(s) (CRI) normally associated with anti-TMA antibodies. In cultures containing TMA-TsF1, CRI+PFC are suppressed by 90-100% while the CRI-PFC are suppressed only by 10-30%. Our studies further show that an induction-phase, antigen-binding, CRI+, and I-J+ single-chain factor is responsible for the observed in vitro suppression. The possibility of utilizing this assay to monitor a variety of antigen-specific suppressor factors is discussed.     

Mechanism controlling the genetic restrictions of an NP-specific suppressor factor that inhibits B cell responses

The mechanism of B cell suppression by a T cell hybridoma-derived monoclonal effector suppressor factor (TsF3) was studied in the 4-hydroxy-3-nitrophenyl acetyl (NP) system. The NP-specific effector suppressor cells that produce TsF3 are Lyt-1-, 2+, I-J+, NP-binding T cells and are induced by immunization with NP conjugates. Monoclonal TsF3 inhibits both T cell activity as measured by suppression of contact sensitivity responses and B cell function as measured by suppression of antibody production to both T-independent and T-dependent antigens. The present studies were designed to specifically investigate the mechanisms and genetic restrictions that govern the interactions between TsF3 and its target cells in the plaque-forming cell (PFC) response. The results show that the target of TsF3 is a splenic adherent cell. Suppression will occur only if the restriction specificity of the TsF3 matches the H-2 genotype of the adherent population. Once this TsF3-adherent cell interaction has occurred, suppression of NP-specific B cells can occur across an H-2 barrier. The data also demonstrate that Igh-linked gene products do not appear to play a part in the TsF3-mediated suppression of in vitro PFC responses, which contrasts with the requirements for regulation of T cell-mediated contact sensitivity responses.     

T suppressor factor activity is due to two separate molecules. The Lyt-1(-)2+I-J+ cells of mice primed with antigen make an antigen binding molecule which is only active when complemented by cofactor made by Lyt-1+2(-)I-J+ cells

Mice primed with picrylsulfonic acid (PSA) and then painted on the skin with picryl chloride produce antigen-specific T suppressor factor (TsF). In contrast unpainted primed mice fail to produce active TsF. This is not due to the absence of the antigen binding part of TsF but to the absence of a cofactor. This cofactor is (a) antigen nonspecific and occurs in potassium chloride extract of normal spleen cells. It also occurs in the 24 hr supernatant of normal cells modified by haptenisation with picryl or the unrelated NP antigen (4-hydroxy-3-nitrophenylacetyl), and in preparations of conventional TsF (PSA/PCl) from painted PSA-primed mice; (b) bears I-J determinants; and (c) is produced by Lyt-1+2(-)I-J+ cells. The antigen binding molecule occurs alone in the supernatant of PSA-primed mice. It lacks I-J determinants and has a molecular weight around 35,000 and 75,000. It is produced by Lyt-1(-)2+I-J+ cells and is only active when complemented by cofactor. However, the complementation is genetically restricted and the restriction maps to the I-J subregion of the MHC.     

Requirements for suppressor T cell activation

Third-order (Ts3) suppressor cells are generated after conventional immunization. These cells, however, will not mediate suppressor cell function unless specifically triggered by an activating signal, termed TsF2. This report analyzes the mechanism of this TsF2-mediated triggering event. TsF2-mediated suppression is genetically restricted by genes in the I-J and Igh-V regions. The target of the I-J restrictions is a firmly adherent accessory cell, which appears to express I-J-related determinants. These accessory cells are sensitive to cyclophosphamide treatment and 500 R irradiation. In contrast, the target of the Igh-V restriction of TsF2 appears to be the Ts3 cell, which carries antigen-specific, idiotype-related receptors. The mechanism of suppressor cell activation appears to involve two stages. Presentation of I-J-restricted TsF2 by I-J-compatible presenting cells and a second step involving idiotype-anti-idiotype interactions between TsF2 and the Ts3 cell. I-J compatibility is not required with the accessory cell for Ts3 activation. Finally, we hypothesize that the anti-idiotypic determinants expressed on TsF2 can serve as an internal image of antigen, thereby permitting specific targeting of the factor.     

Information transfer between T cell subsets is directed by I-J+ antigen nonspecific molecules

T cell antigen-specific suppressor factors (TsF) consist of two distinct polypeptide chains: one that binds antigen (ABM) and one that bears I-J region markers (I-J+ chain). We studied the functional role of these two molecules in delivering the biologic message of suppression to its appropriate target cell. Two different biologically active TsF were used in these studies: TsiF, a T suppressor-inducer factor consisting of an ABM secreted by Ly-1 T cells (Ti-ABM) and an I-J+ subfactor secreted by Ly-1 T cells (I-Ji), which initiates the suppressor circuit by inducing an Ly-1,2 T cell; and TseF, a T suppressor-effector factor consisting of an ABM secreted by Ly-2 T cells (Te-ABM) and an I-J+ subfactor secreted by Ly-1 T cells (I-Je), which delivers the biologic message of suppression to the T helper (TH) cell. In both TsF, the ABM and I-J+ chain are noncovalently associated and can be easily separated. Both molecules must be present, however, for biologic activity of the TsF to be manifest. We studied the role of each chain in delivering these biologically active messages by constructing "hybrid" factors made from mixing the ABM from TsiF with I-J+ chains from either TsiF or TseF and determined which of these chains could reconstitute functional TsiF activity. Likewise, we mixed the AMB from TseF with I-J+ chains of TsiF or TseF to determine which I-J+ chain could reconstitute TseF activity. We found that I-J+ chain from TsiF (I-Ji) can reconstitute ABM from TsiF to form a functional TsiF capable of inducing suppression but cannot reconstitute ABM from TseF to form a functional TsiF capable of suppressing the activity of TH cells. Likewise, the addition of I-J+ chain from TseF to ABM from TseF can reconstitute its ability to suppress TH responses, but I-J+ chain from TsiF plus ABM from TseF has no effect on these TH cell responses. We did find, however, that this hybrid TsF composed of the ABM from TseF and the I-J+ chain from TsiF is capable of suppressing the Ly-1,2 Ttrans cell, the cell normally induced by the ABM + I-J+ suppressor inducer complex from T suppressor-inducer cells (TsiF).(ABSTRACT TRUNCATED AT 400 WORDS)     

Insulin-specific suppressor T cell factors

Murine antibody responses to heterologous insulins are controlled by MHC-linked immune response genes. Although nonresponder mice fail to make antibody when injected with nonimmunogenic variants of insulin, we have recently shown that nonimmunogenic variants stimulate radioresistant, Lyt- 1+2- helper T cells that support secondary antibody responses. However, the helper activity can not be detected unless dominant, radiosensitive Lyt-1-2+, I-J+ suppressor T cells are removed. In this paper we report that extracts of primed Lyt-2+ suppressor T cells contain insulin-specific suppressor factors (TsF) that are capable of replacing the activity of suppressor T cells in vitro. The activity of these factors is restricted by MHC-linked genes that map to the I-J region, and immunoadsorption studies indicated that they bind antigen and bear I-J-encoded determinants. Insulin-specific TsF consists of at least two chains, one-bearing I-J and the other the antigen-binding site. Furthermore, mixing of isolated chains from different strains of mice indicates that the antigenic specificity is determined by the antigen-binding chain and the MHC restriction by the H-2 haplotype of the source of the non-antigen-binding, I-J+ chain. Moreover, mixtures containing antigen-binding chain from allogeneic cell donors and I-J+ chain from responder cell donors have activity in cultures containing responder lymphocytes. This suggests that preferential activation of suppressor T cells, rather than differential sensitivity to suppression, results in the nonresponder phenotype to insulin.     

Nonspecific inhibitor of DNA synthesis elaborated by T acceptor cells. I. Specific hapten- and I-J-driven liberation of an inhibitor of cell proliferation by Lyt-1-2+ cyclophosphamide-sensitive T acceptor cells armed with a product of Lyt-1+2+-specific suppressor cells

Lyt-1+2+ hapten-specific T suppressor cells (Ts) from mice injected and then painted with picryl or oxazolone derivatives produce hapten-specific T suppressor factors (TsF) in vitro. Stimulation by painting with contact sensitizer (which need not be specific) gives rise to Lyt-1-2+, I-J+, cyclophosphamide-sensitive T acceptor cells (Tacc). When the Tacc population is armed with TsF and then is exposed to specific antigen in the context of I-J-controlled determinants (antigen-presenting, haptenized spleen cells and Ts sharing the same I-J subregion), a nonspecific inhibitor of DNA synthesis (nsINH) appears in the supernatant. This inhibitor suppresses the primary DNA synthetic response to concanavalin A, lipopolysaccharide, and alloantigens in both syngeneic and allogeneic lymphocytes. The nsINH is only effective when added to lymphocyte cultures less than 8 hr after the stimulation with concanavalin A. The nsINH, however, affects neither primary nor secondary cytotoxicity in vitro. These data suggest the mouse immune system is capable of selective regulation of the response to specific antigen by the production of nonspecific soluble suppressor factor(s).     

Reconstitution of an inactive antigen-specific T cell suppressor factor by incubation of the factor with prostaglandins

Experiments were performed to test the hypothesis that prostaglandins are crucial to the ability of an antigen-specific T cell suppressor factor to deliver a suppressive signal. In the system employed, T suppressor cells release an antigen-specific factor (TsF) that suppresses the ability of effector cells to transfer contact sensitivity (CS) skin swelling responsiveness to adoptive recipients. Culture of TsF-producing cells in the presence of indomethacin caused production of an inactive TsF that could be reconstituted by incubation of this inactive factor with low concentrations of certain prostaglandins such as PGE2 or PGE1. Subsequently, nearly all the prostaglandins were removed by dialysis, and the reconstituted TsF then acted as an antigen-specific suppressor of CS effector cells. Neither the inactive factor nor prostaglandins were suppressive alone. Furthermore, the prostaglandins are crucial to the constitution of TNBSA-F, the non-antigen-binding subunit of the TsF that probably delivers the ultimate suppressive signal. These results provide a new type of antigen-specific role for prostaglandins in immunoregulation and indicate that simple, local, hormonal molecules in physiologic concentrations can have a crucial and long-lasting role in constituting the suppressive activity of antigen-specific regulatory macromolecules released by suppressor T cells.     

T suppressor efferent circuit which affects contact sensitivity to picryl chloride: the late-acting, second nonspecific T suppressor factor bears I-A determinants which are responsible for the I-A genetic restriction in its interaction with its target cell

The T suppressor efferent circuit in the picryl (TNP) system, which inhibits the passive transfer of contact sensitivity, involves at least two antigen-nonspecific factors. The second nonspecific T suppressor factor (ns-2) bears I-A determinants of both the alpha and the beta chain as shown by affinity chromatography on immobilized anti-I-A monoclonal antibodies. Sequential absorption shows that the determinants of the alpha and beta chain occur on the same molecular complex. No absorption was obtained with anti-I-E antibody. There are two genetic restrictions associated with ns-2--the first is in its release from the second T suppressor efferent cell (on exposure to antigen) and the second is in its inhibitory interaction with its target cell. Both are MHC restricted and matching in I-A (but not I-E, or I-J) is sufficient. The question was asked whether the I-A of the ns-2 was directly responsible for the I-A genetic restriction in its action. F1 TsF was made in (H-2k X H-2b)F1 mice by injecting picrylated parental cells intravenously and triggering the release of ns-2 with the corresponding picrylated parental cells. Both I-Ak- and I-Ab-positive ns-2 were produced and were separated by affinity chromatography on immobilized anti-I-A monoclonal antibody. The I-A phenotype of these separated ns-2 of F1 origin determines the genetic restriction in their action; i.e., I-Ak+ ns-2 only inhibits passive transfer by H-2k cells and I-Ab+ ns-2 only acts on H-2b cells. In contrast, the I-A haplotype of the picrylated cell used to induce the Ts cell which makes ns-2 is unimportant. It was concluded that the I-A on the ns-2, and not a possible recognition site for I-A, serves as a restriction element. This finding suggests that ns-2 may act directly on the I-A-restricted T cell which mediates contact sensitivity.     

Antigen-specific T cell-mediated suppression. II. In vitro induction by I-J-coded L-glutamic acid50-L-tyrosine50 (GT)-specific T cell suppressor factor (GT-T8F) of suppressor T cells (T82) bearing distinct I-J determinants.

The induction of new suppressor T cells (Ts2) by suppressive extracts (TsF) from L-glutamic acid50L-tyrosine50 (GT) nonresponder mice was examined. Incubation of normal spleen cells with allogeneic GT-TsF for 2 days in vitro led to the generation of Ts2 cells able to suppress subsequent responses to the immunogen GT-methylated bovine serum albumin (GT-MBSA) in vivo. This induction occurred efficiently when TsF donor and target cells differed at all of H-2, including the I-J subregion. B10.BR (H-2k) GT-TsF, adsorbed on, then acid eluted from GT-Sepharose and anti-I-Jk [B10.A (3R) anti-B10.A (5R)]-Sepharose in a sequential fashion could induce BALB/c (H-2d) spleen cells to become Ts2 only if nanogram quantities of GT were added to the purified GT-TsF. This indicates a requirement for a molecule or molecular complex possessing both I-J determinants and antigen (GT)-binding specificity, together with GT itself, for Ts2 induction. The induced Ts2 are I-J+, since their function can be eliminated by treatment with anti-I-Jk plus C. These I-J determinants are coded for by the precursor of the Ts2 and do not represent passively adsorbed, I-J coded TsF, since anti-Ijk antiserum [(3R X DBA/2)F1 anti-5R] which cannot recognize the BALB/c (I-Jd) TsF used for induction still eliminates the activity of induced A/J (I-Jk) Ts2. These data provide further evidence for and information about the minimum of two T cells involved in antigen-specific suppressor T cell systems.     

Accessory cells in immune suppression. III. Evidence for two distinct accessory cell-dependent mechanisms of T lymphocyte-mediated suppression

Suppression of antibody secretion by the 2,4,6-trinitrophenol (TNP)-binding BALB/c myeloma, MOPC 315, by idiotype- and hapten-reactive suppressor T cells is mediated by secreted factors (TsF) and requires the presence of accessory cells (AC). Idiotype-specific TsF functions only in the presence of Ia+ AC and is completely idiotype specific. Moreover, no suppression is observed when myeloma targets and AC are separated by cell-impermeable membranes, indicating that the role of AC may be to bind, focus, and/or present TsF to the myeloma cells. In contrast, TNP-specific TsF inhibits myeloma function in the presence of TNP-protein and activated macrophages that are not Ia+. This form of suppression is nonspecific at the effector stage; i.e., anti-TNP TsF inhibits a non-TNP binding cell line, TEPC 15, as long as TNP-protein and activated macrophages are present. Moreover, suppression occurs even when myeloma targets and AC are separated by cell-impermeable membranes. These results are consistent with the view that hapten-reactive TsF binds to antigen on the surface of macrophages and induces these cells to secrete nonspecific immunosuppressive molecules. Thus, different types of AC may play fundamentally different roles in TsF-mediated suppression; they may either bind and present TsF to targets (as in the case of idiotype-specific TsF) or secrete nonspecific immunosuppressants as a consequence of a TsF-antigen interaction (hapten-specific TsF). Autonomous, suppressible targets provide valuable experimental systems for analyzing the cellular interactions in T cell-mediated suppression.     

Characterization of an antigen-specific suppressive factor derived from a cloned suppressor effector T cell line

A cloned effector-type suppressor T cell line, 3D10, which is known to suppress the antibody response against dinitrophenylated keyhole limpet hemocyanin (KLH), produced a soluble KLH-specific factor (TsF) that can replace the function of parental T cell clones. High activity of TsF was released spontaneously into the culture supernatant when cultured in interleukin 2 (IL 2)-containing medium, requiring no antigenic stimulation. The culture supernatant of 3D10 was also capable of inhibiting the KLH-induced proliferative response of primed T cells in an antigen-specific manner. The direct target of TsF was found to be Lyt-1+2- T cells undergoing an early stage of antigen-specific proliferation. TsF was antigen binding but lacked any other serologic markers such as I-J and immunoglobulin heavy chain-linked allotypic determinants on T cells. No genetic restriction was found in its action on allogeneic T cells. The production of IL 2 in proliferative T cells by antigenic stimulation was not inhibited by TsF. These results indicate that the TsF described here is the legitimate mediator produced by the effector-type suppressor T cell that suppresses the antigen-specific responses of Lyt-1+2- T cells. The m.w. of TsF was approximately 75,000.