An antigen-specific signal is required for the activation of second-order suppressor T cells in the regulation of delayed-type hypersensitivity to 2,4,6-trinitrobenzene sulfonic acid

Inhibition of lymphocyte kinase Lck and phosphatidylinositol 3-kinase by a novel immunosuppressant, lymphostin

Lck is a Src-family tyrosine kinase that is expressed predominantly in T cells, where it plays important roles in T-cell activation. Lymphostin was isolated from Streptomyces sp. as an inhibitor of Lck. As previously reported, lymphostin inhibited Lck (IC50 0.05 microM) and the mixed lymphocyte reaction (IC50 0.009 microM). We have now examined the mechanism of inhibition by lymphostin. Lymphostin inhibited protein-tyrosine kinase activity in Jurkat T cells, demonstrating the effectiveness of the compound at the cellular level. Furthermore, lymphostin suppressed delayed-type hypersensitivity in mice. However, the inhibitory activity against Lck at the cellular level was weaker than that against the mixed lymphocyte reaction. Thus, we examined the effects of lymphostin on other kinases. Interestingly, lymphostin also inhibited phosphatidylinositol 3-kinase (IC50 0.001 microM). Consequently, we conclude that lymphostin inhibits the mixed lymphocyte reaction and delayed-type hypersensitivity not only through the blockade of Lck, but through the blockade of phosphatidylinositol 3-kinase as well.

Ultraviolet-induced suppressor T cells and factor(s) in murine contact photosensitivity. III. Mode of action of T-cell-suppressor factor(s) and interaction with cytokines

The mode of action of T-cell-suppressor factor (TsF) induced by ultraviolet B (UVB) preirradiation in terms of interaction with several cytokines was studied. Suppression of murine contact photosensitivity (CPS) to 3,3',4',5-tetrachlorosalicylanilide (TCSA) by preirradiation of the sensitizing site to low doses of UVB was caused by antigen-specific suppressor T cells (Ts) and was not associated with the generation of efferent limb-acting suppressor cells. TsF released by Ts inhibited the proliferation of immune lymph node (LN) cells in vitro and reduced interleukin (IL)-2 production of these cells in an antigen-specific fashion without affecting the IL-2 receptor (IL-2R) expression. Both rIL-2 and rGM-CSF have the ability to restore CPS responses in the UVB-preirradiated mice when administered after but not before photosensitization. However, rIL-2 but not rGM-CSF counteracted the in vivo inhibitory effect of TsF. rGM-CSF did not affect the density of I-A+ epidermal Langerhans cells (LCs). It was suggested that TsF inhibited IL-2-mediated immune T-cell proliferation, while rGM-CSF reconstituted the CPS by enhancing the function of photodamaged LCs. These results indicate multiple steps of the UVB-induced immunosuppression circuit, each of which seems to be controlled by different immunomodulators.

The role of suppression in immunoregulation: in vivo analysis using a monoclonal antibody to T suppressor factors

We have used a monoclonal antibody (mAb)-specific for murine T suppressor (Ts) cells (mAb 14-12) to study the role of T cells in tolerance and immunoregulation. We demonstrate that mAb 14-12 can block in vivo Ts cell activity in a variety of experimental systems. It prevents the induction of Ts cells induced by i.v. injection of the water-soluble hapten 2,4,6-trinitrobenzene sulfonic acid, and the protein antigen bovine serum albumin. When 14-12 mAb is given prior to the i.v. injection of trinitrophenyl-conjugated spleen cells (TNP-SC) it blocks the induction of Ts cells and sufficiently overcomes suppression so that TNP-SC is able to induce immunity. mAb 14-12 can convert nonresponder mice into responders for the Ir gene-controlled response to the random terpolymer L-glutamic acid60-L-alanine30-L-tyrosine 10 (GAT), and can substitute for cyclophosphamide in overcoming a suppressor barrier in the adoptive transfer of contact sensitivity. Administration of 14-12 mAb just prior to immunization results in the augmentation of contact sensitivity, antibody and plaque-forming cell responses. These results demonstrate the versatility of this reagent for the study of Ts cell activity.

Calorie restriction modifies the delayed-type hypersensitivity response to the hapten trinitrobenzenesulfonic acid and to hapten-modified syngeneic spleen cells

We have studied the influence of different degrees of calorie restriction on the induction and the regulation of the delayed type hypersensitivity (DTH) response to trinitrobenzenesulfonic acid (TNBS) and TNBS-modified spleen cells (TNBS-SC), injected by the sc or the iv route. Immediately after weaning, BALB/c mice were placed on restricted diets for either 2 or 4 weeks and then the DTH response was induced. The results showed that a 37.5% restriction in the food supply significantly depressed the level of the DTH response induced by the sc injection of TNBS-SC. In contrast, a 25% restriction in the food supply was insufficient to depress the response. Calorie restriction did not modify the inhibitory influence of an iv injection of TNBS-SC on the DTH response. However, iv presensitization with free hapten or the simultaneous injection of TNBS-SC by the iv and the sc routes did not significantly depress the DTH response in calorie-restricted mice, indicating a defect in the inhibitory regulation of the DTH response in these dietary groups.

Sensitization through carcinogen-induced Langerhans cell-deficient skin activates specific long-lived suppressor cells for both cellular and humoral immunity

Application of 2,4-dinitrofluorobenzene (DNFB) to BALB/c mouse skin depleted of epidermal Langerhans cells (LC) by the chemical carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) activated cells which suppress both contact sensitivity and antibody production when transferred into naive host mice. Tolerance was induced by a concentration of DNFB optimal for inducing contact sensitivity in solvent-treated control mice. The cellular and humoral responses of hosts to a second antigen, 2,4,6-trinitrochlorobenzene (TNCB), were unaffected by these suppressor cells, demonstrating specificity for DNFB. Suppressor cells for cellular and humoral immunity could still be demonstrated 6 months following activation, by which time some mice had died, presumably of old age. The dose responses to sensitizer for generation of cells which suppressed contact sensitivity and antibody production differed, indicating that separate populations of suppressor cells probably inhibit these responses. Hence, during cutaneous chemical carcinogenesis, depletion of LC may allow activation of specific long-lived suppressor cells capable of inhibiting cellular or humoral antitumor immune responses.

The use of nonspecific T acceptor cells to overcome the aberrant function of antigen-specific third-order T suppressor cells

Earlier studies in the phenyltrimethylamino (TMA) hapten system demonstrated that under certain conditions idiotype-specific second-order T suppressor (Ts2)-bearing mice fail to suppress TMA-specific delayed-type hypersensitivity. This was due to a functional deletion in the third-order T suppressor (Ts3) subset. In this report we have confirmed and extended these findings to show that only homologous TMA-specific Ts3 can restore suppressor function, both heterologous Ts3 and unprimed T-cell populations failed to do so. Furthermore, attempts to induce Ts3 function in the defective mice after reconstitution with normal precursor Ts3 cells also failed. In contrast, protocols which induce heterologous contact and cutaneous hypersensitivity reactions readily induced cell populations capable of restoring suppression in the Ts3-defective mice. Analysis of the lymphoid populations from the contact-sensitized defective mice revealed that these cells were not the prototypical Ts3 but were similar to the previously reported nonspecific T acceptor cell. The results further indicated that the T acceptor cell functioned as the active terminal-phase Ts subset, and this could be used as an alternative to the TMA-specific Ts3. The importance of multiple suppressor pathways at the terminal phase of immune suppression is discussed.

Characterization of a third-order suppressor T cell (Ts3) induced by cryptococcal antigen(s)

Previous studies from our laboratory have shown that a high dose of cryptococcal culture filtrate antigen (CneF) administered intravenously induces a complex suppressor cell cascade which down-regulates the cell-mediated immune response to Cryptococcus neoformans antigens. The primary objective of this investigation was to determine whether a suppressor cell induced by immunization is required for efferent suppression of the cryptococcal delayed-type hypersensitivity (DTH) response. Our approach to this problem was to immunize CBA/J mice with CneF emulsified in complete Freund adjuvant and then 6 days later to collect spleen cells from the immunized mice and adoptively transfer these cells along with C. neoformans-specific second-order suppressor T cells (Ts2) to naive syngeneic recipients at the time of footpad challenge of the recipients with CneF. To establish which populations of cells in the spleens of immunized mice play a suppressive role, mass cytolysis with specific antibodies and complement was performed before the spleen cells were transferred to naive animals. Since the phenotype of the cells responsible for the transfer of the cryptococcal DTH response had not been completely determined, we first demonstrated that the cells responsible for DTH were L3T4+ Lyt-2- cells. Subsequently, we established that a Thy-1+ L3T4- Lyt-2+ I-J+ cell population induced by immunization was required along with C. neoformans-specific Ts2 cells for efferent suppression of the cryptococcal DTH response. In addition, we demonstrated that the suppressor cells in the immune cell population were derived from cyclophosphamide-sensitive precursors. These data indicate that a third suppressor cell population is required for efferent suppression of the cryptococcal DTH response. As in the azobenzenearsonate and 4-hydroxy-3-nitrophenyl acetyl hapten suppressor models, the Ts2 cells in the circuit mediate their effects through this third suppressor component. Since the mode of induction and the phenotype of the third C. neoformans-specific suppressor cells are similar to those reported for Ts3 cells in other antigen-specific suppression models, we referred to this third suppressor cell in the C. neoformans-specific suppressor cell cascade as a Ts3 cell.

A novel suppressive activity: complementation between a T cell induced with first-order T-suppressor factor and an I-J-restricted antigen-nonspecific T cell

Previous studies demonstrated that the first-order T-suppressor factor (TsF1) requires the presence of antigen to induce idiotype-specific Ts cells which readily suppress phenyltrimethylamino (TMA) hapten-specific delayed-type hypersensitivity (DTH) responses when transferred into already immune recipients. In this study we show that TsF1 in the absence of antigen induces a splenic population which limits DTH in recipient mice only when an additional accessory lymphoid population was also cotransferred. Neither of these populations alone was sufficient to mediate suppression and depletion of T cells in either population's abrogated suppression, indicating the T-cell dependency of the complementing cell types. Moreover, suppression was seen only when TMA-TsF1-induced and not normal spleen cell lysate-induced cells were cotransferred with the antigen-induced population, suggesting the requirement for a specific signal to induce the factor-induced population. Further experiments showed that the antigen-induced lymphoid population could be replaced by either heterologous antigen-induced or adjuvant alone-induced splenic populations, indicating the lack of specificity of this secondary population. Further analysis showed that the cell complementation between TMA-TsF1-induced and the nonspecific accessory lymphoid population resulted in antigen-specific and genetically restricted immune suppression. The TsF1-induced lymphoid population was not responsible for the genetic restriction, and furthermore, there was no restriction observed between the two complementing populations. However, matching of the nonspecific accessory cell with the recipient host at the I-J subregion of the H-2 complex was essential for immune suppression. Finally, the activity of complementing cells was found to be independent of cyclophosphamide-sensitive Ts populations of the recipient mice. The ramifications of these findings with reference to the existing suppressor pathways are discussed.

Specific suppressor T cells in rats active in the afferent phase of contact hypersensitivity

The optimal conditions for the induction of contact hypersensitivity in rats and the characteristics of its suppression were studied using the sensitizing haptens dinitrofluorobenzene (DNFB) and trinitrochlorobenzene (TNCB). The hypersensitivity was shown to be hapten specific in so far as TNCB did not sensitize for DNFB responses but sensitization with DNFB did allow a marginal response in rats challenged with TNCB. Suppression of the sensitization to DNFB and TNCB could be generated by intravenous injection of dinitrobenzenesulphonic acid (DNBS) or trinitrobenzenesulphonic acid (TNBS), respectively, up to 3 weeks before sensitization. This suppression was hapten specific and could be transferred with splenic T cells enriched for lymphocytes carrying the OX8 (Tc/s) cell marker. Only the induction phase of sensitization, however, could be suppressed in that way. No suppression acting upon the effector phase could be detected except for a nonspecific local suppression at the site of a previous challenge with an antigen to which the rat was specifically suppressed. This study shows that suppression of contact hypersensitivity in rats is mediated by specific suppressor T cells of which the activation pathway apparently differs from that postulated for mice.

Induction and persistence of suppression of contact hypersensitivity against bystander haptens and alloantigens in rats

The shift of suppression from a tolerizing hapten to a so-called bystander antigen was investigated in this study using contact hypersensitivity to trinitrochlorobenzene (TNCB) and dinitrofluorobenzene (DNFB) and delayed type hypersensitivity (DTH) to alloantigens in the rats as experimental models. Primary suppression of contact hypersensitivity was induced by intravenous injection of the water-soluble forms of TNCB and DNFB. A shift of the suppression to the bystander hapten was found if the tolerizing and bystander hapten were mixed and applied to the same area of skin during the sensitization procedure, but not if they were applied to separate areas of skin. With alloantigens, bystander suppression developed only when the sensitizing allogeneic cells were mixed with hapten-modified syngeneic cells. It was not induced by hapten-modified allogeneic cells. Once induced, such bystander suppression of the response to haptens persisted independently of the primarily tolerizing hapten, and it could be adoptively transferred with spleen cells. These results favour the concept that the bystander suppression is mediated by the non-specific action of suppressor cells generated specifically during the mixed sensitization rather than by an antigen bridge.

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.

In vivo activity of interleukin-2: conversion of a stimulus causing unresponsiveness to a stimulus causing contact hypersensitivity by the injection of interleukin-2

The intravenous injection of hapten-modified (picrylated) cells causes unresponsiveness. When conventional or recombinant interleukin-2 (IL-2) is also injected, strong contact sensitivity occurs. This IL-2 is effective when given 7 hr after the injection of the picrylated cells or 2 days later, but has no effect when given beforehand. It is suggested that picrylated cells given intravenously fail to induce contact sensitivity secondary to a failure of IL-2 production, and that IL-2 may be one of the second signals which converts a 'tolerogenic' stimulus into an immunogenic stimulus.

Antigen-specific augmentation of delayed-type hypersensitivity by immune serum factor in mice

The serum from C3H/He mice immunized with chicken erythrocytes (CRBC) in complete Freund's adjuvant contained a factor able to augment delayed-type hypersensitivity (DTH) antigen specifically, when transferred into naive syngeneic recipient mice before their sensitization with CRBC. This activity in immune serum appeared on Day 4 and reached a peak on Day 8 after immunization, and was enhanced when donor mice were treated with cyclophosphamide (CY) 2 days before immunization. The ability of recipient mice to respond to this factor was enhanced by CY treatment of these mice 4 days before being transferred. This factor could be discriminated from conventional antibodies. Production of this factor in the serum donor and the expression of its activity in transferred recipient was mediated by a T-cell subset which showed a low degree of thymus dependency in ontogenic development.

Tubular antigen-derivatized cells induce a disease-protective, antigen-specific, and idiotype-specific suppressor T cell network restricted by I-J and Igh-V in mice with experimental interstitial nephritis

The nephritogenic effector T cell response producing interstitial nephritis in mice can be largely inhibited by the adoptive transfer of suppressor T cells before or after the induction of disease. These suppressor T cells are harvested from donor mice primed with tubular antigen-derivatized syngeneic lymphocytes, and two subsets of suppressor cells can be characterized within this donor cell population. The first suppressor cell in this network is an L3T4+, I-J+, RE-Id+ cell (Ts-1). Ts-1 cells are antigen-binding suppressor cells that inhibit afferent phase immune responses and, in the presence of tubular antigen, specifically induce Lyt-2+, I-J+ cells (Ts-2) that are antiidiotypic (RE-Id-binding) suppressors. The Ts-2 cell is functionally restricted in its suppressive effect by I-J and Igh-V gene products, and acts on the effector limb of the cell-mediated anti-tubular basement membrane immune response. These studies provide an experimental basis for further efforts to use immunoregulatory modulation in the control of autoimmune renal disease.

The control of the contact sensitivity skin reaction: T-suppressor afferent cell blocks the production of antigen-specific T-helper factor

Lymph node cells from mice painted with the contact sensitizers picryl chloride or oxazolone produce antigen-specific T-helper factor. This is detected by its ability to increase the contact sensitivity response to the injection of small numbers of haptenized spleen cells into the footpads of naive recipients. The production of this T-helper factor is inhibited by the injection of spleen cells from mice given water-soluble, chemically reactive hapten such as picrylsulphonic (trinitrobenzenesulphonic) acid--an agent which induces unresponsiveness. The cells which inhibit the production of T-helper factor are antigen-specific T-suppressor cells. They are sensitive to cyclophosphamide given before the injection of picrylsulphonic acid, but are unaffected by adult thymectomy. In this respect, they resemble the family of Ts-aff which inhibit the development of contact sensitivity, specific antigen-induced lymph node proliferation and the specific IgG response, and differ from the T-suppressor efferent cell (Ts-eff) which acts at the expression stage of the contact sensitivity reaction. These results are fully compatible with the view that the Ts-aff inhibits the development of contact sensitivity by blocking the production of antigen-specific T-helper factor.

Immunoregulation of lysozyme-specific suppression. II. Hen egg-white lysozyme-specific monoclonal suppressor T cell factor suppresses the afferent phase of delayed-type hypersensitivity and induces second-order suppressor T cells

Culture supernatant from a monoclonal T cell lymphoma line (LH8-105) obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme (HEL)-specific suppressor T lymphocytes is able, when injected into mice, to specifically suppress the delayed-type hypersensitivity (DTH) reaction induced by HEL. The suppressor T cell factor (TsF) exhibits fine antigenic specificity since it suppresses the DTH response induced by HEL without affecting the DTH response induced by ring-necked pheasant egg-white lysozyme (REL), a lysozyme closely related to HEL. Conversely, LH8-105 TsF is able to suppress the DTH response induced by human lysozyme, distantly related to HEL but sharing a common epitope critical for induction of suppressive activity. The fine antigenic specificity of LH8-105 TsF for a restricted epitope on the HEL molecule is confirmed by binding to HEL but not to REL immunosorbents. This TsF also bears I-J determinants, as demonstrated by binding to monoclonal anti-I-J immunosorbents, and it suppresses the afferent but not the efferent phase of the DTH response to HEL. The afferent suppression is controlled by genes apparently mapping in the I-J subregion of the H-2 complex since I-J-incompatible mice are not suppressed by LH8-105 TsF injection. This inducer-type TsF induces second-order effector suppressor T cells only in HEL-primed mice indicating the primary role of antigen, in association with H-2 (I-J) products, in the afferent portion of this suppressive circuit.

Tumor bearer T cells suppress Bacillus Calmette-Guérin-potentiated antitumor responses. III. Identification of an auxiliary efferent suppressor-T-cell population

T cells (Ts-eff) induced in BALB/c mice by subcutaneous (sc) growth of syngeneic Meth A tumors can adoptively suppress the effector phase of delayed-type hypersensitivity (DTH) in Bacillus Calmette-Guérin (BCG)-primed and unprimed recipients which have been sensitized with irradiated Meth A cells but they do not inhibit the augmented DTH response in recipients inoculated with cyclophosphamide (CY) 2 days prior to sensitization. By reconstituting CY-treated immunized recipients with selected spleen cell populations, it has been demonstrated that Ts-eff suppress DTH by interacting with a second or auxiliary suppressor cell population present in immune but not normal spleens. These auxiliary suppressor cells (Ts-aux) are Thy+, Lyt 1-2+ and I-J+, phenotypically similar to Ts-eff. Their activity is not influenced by B-cell depletion. Unlike Ts-eff, Ts-aux do not bear receptors specific for Meth A cells. Ts-aux and Ts-eff share similar sensitivity to irradiation and high dose (100 mg/kg) CY but unlike Ts-eff, Ts-aux are cortisone sensitive, nondividing, nonadherent cells which are absent from the thymus. The phenotype and mechanism of action of Ts-aux resemble those of the auxiliary or Ts3 cells defined in models of contact sensitivity, DTH to simple haptens, and in vitro antibody responses.