Biomedical subjects

M Zöller

Publications and source records attributed to M Zöller.

At least 127 records · Page 7Linked to original sources

PubMed1987

Transmission of hapten-specific tolerance to an unrelated carrier.

The principle of linked recognition is well defined in response and suppression. Yet, to our knowledge, it is not explored in the context of tolerance. To investigate, whether the status of tolerance toward a hapten (TNP) can be transferred to a subsequently introduced carrier, animals which were tolerized by a subimmunogenic dose of hapten (TNP) coupled to syngeneic monoclonal anti-TNP IgG, with the rationale of combining the phenomena of low zone tolerance and syngeneic IgG-induced suppression, were challenged with TNP-horse red blood cells (HRBC). Conjugates of high density (40 mM) TNP-syngeneic IgG (TNP40-IgG) were immunogenic and after challenge with TNP-HRBC, animals responded to TNP and to HRBC. Yet, spleen cells (SC) of mice injected with TNP2.5-IgG and challenged with TNP-HRBC were tolerant against TNP as well as the carrier. Limiting dilution (LD) analysis revealed that subimmunogenic doses of TNP coupled to IgG resulted in diminished activation of help, failure to activate contrasuppressor T cells (TCS), and significantly augmented activation of suppressor T cells (TS). On the other hand, after challenge with TNP-HRBC, activation/expansion of carrier-specific helper (TH), suppressor, and contrasuppressor T cells were not affected by previous immunization with subimmunogenic or immunogenic doses of TNP-IgG conjugates, but HRBC-specific TCS could not interact with TNP-specific TS. Hence, to initiate tolerance it was necessary (and sufficient) that an activated and expanded TS population was not counterregulated by TCS. In this situation, an established status of dominance of suppression for the epitope TNP could not be disrupted by an immunogene carrying a multitude of new epitopes; i.e., tolerization by subimmunogenic doses of the individual epitope TNP resulted in unresponsiveness against any immunogen carrying this epitope.

Animals↗

PubMed1987

Hyperreactivity of adult BALB/c mice tolerized at birth with TNP-ovalbumin.

BALB/c mice injected with 0.2 mg TNP-ovalbumin (OA) within 24 hours after birth showed reduced levels of functionally active TNP-specific B cells and, accordingly, of plaque-forming cells (PFC) after challenge with carrier-bound TNP until the age of 8 weeks. Yet, when B cells of tolerized mice were cultured in the absence of antigen, a significant number of anti-TNP PFC were detected. Challenge of neonatally tolerized mice at older age with T-dependent or T-independent antigens led to a continuously increasing response towards TNP, which was dominated by IgG-producing B cells. At the age of 8 months, a five-fold augmentation of TNP-specific B cells and of anti-TNP antibodies (AB), as compared to animals treated accordingly as adults, was observed. Clonal analysis of regulatory cells revealed 2 populations of helper (Th1 and Th2) and suppressor (Ts1 and Ts2) T cells in spleen cells (SC) of tolerized mice. In SC of mice immunized as adults, Th1 and Th2, but only one Ts populations were observed. The frequencies of Th1 and Ts1 were in the same range in animals immunized neonatally or as adults. After challenge, frequencies of regulatory cells remained constant in animals immunized as adults. But, in neonatally tolerized mice, challenge resulted in increased frequencies of Th1 and Th2; Ts1 remained constant, and concomitantly the frequency of Ts2 declined significantly. The data are interpreted as newborn tolerance being due to transient B cell anergy via receptor blockade as well as inactivation of AB-producing cells. Neither deficiency in TNP-specific help nor dominance of TNP-specific suppression is involved in maintainance of tolerance, but tolerance appears to be sustained by interference of TNP-specific regulatory cells with anti-idiotypic regulatory cells (Th2, Ts2). Supposing a system of circular network interactions, activation of anti-idiotypic clones will be counterregulated/balanced by activation of antigen-specific clones. Thus, decreasing idiotypic connectivity during life may result in overshooting reactivity of neonatally tolerized mice at older age.

Animals↗

PubMed1987

Regulation of carrier-specific response via a haptenic epitope.

Influences of haptenic epitopes on the regulation of carrier-specific responses are of importance in vaccination and heterogenization protocols. This situation was modelled by analysing the primary and secondary anti-horse red blood cell (HRBC) response under the influence of a haptenic epitope (trinitrophenol, TNP). Primary and secondary anti-HRBC responses were diminished in the presence of TNP. The primary response against the carrier was delayed in the presence of TNP and primary and secondary anti-carrier responses vanished more rapidly in response to TNP-HRBC than in response to HRBC. When frequencies of HRBC-specific B cells were determined under limiting dilution (LD) conditions, a lower frequency of HRBC-specific B cells was discovered in the presence of TNP-HRBC as compared to HRBC. Accordingly, after priming with HRBC, the frequency of B cells was increased by a factor of 49, while after priming with TNP-HRBC the frequency was only increased by a factor of 11. Furthermore, haptenic epitopes influenced the anti-carrier response via regulatory elements. Under physiological conditions, hapten-specific help was insufficient and hapten-specific B cells competed for carrier-specific helper T cells (TH). Suppression was more efficient in hapten-carrier-primed mice than in carrier-primed mice and in line with this observation, an increased frequency of suppressor T cells (Ts) was observed in LD cultures when TNP-HRBC instead of HRBC were used as antigen. It is concluded that haptenic epitopes are relevant for the anti-carrier response, since hapten-specific B cells compete for carrier-specific help, hapten-specific suppression down-regulates carrier-specific help, and the hapten may hide immunogenic epitopes of the carrier, resulting in incomplete activation of the B-cell repertoire.

Animals↗

PubMed1987

Trinitrobenzenesulphonic acid-induced unresponsiveness at the systemic level.

To investigate the mechanism underlying B-cell tolerance, which is still discussed as being the consequence of (functional) clonal deletion or suppression, limiting dilution (LD) analysis of the frequencies of B cells as well as regulatory cells after tolerance induction with trinitrobenzenesulphonic acid (TNBS) was performed. It was shown that the frequency of functionally active hapten-specific B cells was decreased to less than 10% of the frequency in untreated BALB/c mice. After an immunogenic challenge, trinitrophenyl (TNP)-specific B cells of tolerized mice expanded, but did not reach the level of TNP-specific B cells in untreated mice. The expansion of TNP-specific B cells in TNBS-tolerized mice after challenge with TNP-horse red blood cells (HRBC) as observed in LD cultures was in contrast to the absence of anti-TNP plaque-forming cells (PFC) in freshly harvested spleen cells (SC) and the non-detectability of anti-TNP antibodies (AB). Hence, the functional deletion (= anergy) of B cells in vivo appears to be sustained by regulatory cells. Analysis of the regulatory compartment revealed that tolerance induction resulted in transient augmentation of TNP-specific helper T cells (TH), continuously elevated levels of suppressor T cells (TS), and a low level of contrasuppressor T cells (TCS). But, contrary to non-tolerized mice, TCS of tolerized mice were rather refractory to stimulation with TNP-HRBC. Hence, we would like to hypothesize that clonal anergy of B cells leads to inappropriate activation of TCS, whose nominal antigens are antibodies. This in turn sustains the persistence of high levels of TS, i.e. tolerance would be maintained by interruption of feedback activation of regulatory cells via effector cells/molecules.

Animals↗

PubMed1987

Activation of help and contrasuppression as essential prerequisites for immune response.

The network theory proposes the immune system as a self-centered defense mechanism, which continuously maintains a steady state of activity via idiotypic-anti-idiotypic interactions. In line with this hypothesis, the steady state of the immune system has been described to represent a status of suppressed activity, response being manifested by release from suppression. There is evidence that release from suppression is initiated by activation of contrasuppressor cells (TCS), which either transfer a state of resistance towards suppression on helper T-cells (TH) or interact directly with suppressor T-cells (TS). In the latter case, it was postulated that the nominal antigen of contrasuppressor T-cells are antibodies and that TS and TCS interact one with the other via idiotypic-anti-idiotypic structures. The present report examined the role of TCS in initiation of response and proved that the responding state requires activation of TH as well as TCS. While antigenic stimulation (TNP) resulted in concomitant activation of TH and TCS, it was possible to dissect these two prerequisites for response by application of a monoclonal anti-TNP antibody (AB) carrying a recurrent idiotype (Sp6) followed by application of a subimmunogenic dose of the nominal antigen. Clonal analysis of regulatory cells via limiting dilution (LD) cultures revealed that a subimmunogenic dose of antigen led to activation of help but failed to activate TCS. On the other hand application of AB, which did not initiate response, resulted in activation of TCS, but not in activation of TH, i.e., these were not released from suppression. However, consecutive activation of TCS via AB and of help via a subimmunogenic dose of antigen moved the immune system into the responding state. Activation of TCS via AB was found to be independent from the mode of application, i.e., free AB, AB coupled to syngeneic cells, or AB coupled to the nominal antigen, although most straightforward results were obtained with free AB, since syngeneic cells exerted an additional suppressive effect, and AB-antigen (TNP) conjugates activated TNP-specific TH as well as TCS. Furthermore, AB-induced activation of TCS was independent of the recipient's age. Yet, the effect was most pronounced when AB were applied neonatally, i.e., after a hyporesponsive stage, animals were hyperreactive towards the nominal antigen, and this hyperreactivity was initiated by expansion of TCS. This extends the notion of high idiotypic connectivity in the neonatal period to the level of regulatory T-cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1986

Activation of idiotype-specific suppressor T cells by injection of antibody carrying a recurrent idiotype.

Intravenous injection of spleen cells (SC) coated with an antitrinitrophenyl (anti-TNP) IgM monoclonal antibody, Sp6 (Sp6-SC), which carries a recurrent idiotype, resulted in activation of a Lyt-2-positive population which did adhere to Sp6-coated plates. No effect of Sp6-SC injection could be observed in vivo on an anti-TNP B-cell response when mice were primed with an immunogenic dose of TNP-horse red blood cells (HRBC), but an anti-TNP response was observed when Sp6-SC-injected mice were primed with a subimmunogenic dose of TNP-HRBC. Furthermore, after intravenous (iv) injection of Sp6-SC, it was no longer possible to suppress a primary anti-TNP response by iv injection of TNP-haptenized thymocytes. In vitro analysis showed that the Sp6-induced suppressor T cell (Ts) population had no measurable influence on TNP-specific naive B cells, nor did it suppress TNP-specific helper T cells (THTNP), but it did lead to counterregulation of TNP-specific suppressor T cells (TsTNP). Hence, iv injection of antibody carrying a recurrent idiotype resulted in activation of a Ts population which functioned as inhibitor of suppression, thus displaying a helper effect.

Animals↗

PubMed1986

Acquired resistance towards immune defense during metastatic progression represents a secondary phenomenon.

The role of natural immune defense in the control of metastatic spread of tumor cells was evaluated by adapting an s.c.-grown, antigenic, but non-immunogenic rat fibrosarcoma (Bsp6S) to ascitic growth (BSp6A) in the strain of origin (BDX), where peritoneal cells display a high level of NK and macrophage activity. Parallel tests were performed to determine whether tumor cells can selectively adapt to non-specific immune defense, i.e. whether antigenicity of the non-immunogenic tumor remains unaltered, and whether this is accompanied by metastatic progression. During adaptation to ascitic growth the tumor line gradually lost susceptibility to NK cells and macrophages. This was due to the appearance of an increasing number of resistant clones (BSp6S, none; BSp6A, 50% of clones), which had lost binding structures for NK cells and macrophages. No alteration could be observed in antigenicity of the BSp6A variant as revealed by clonal analysis using LD of CTL. Neither BSp6S nor BSp6A cells metastasized. When the ascitic variant was retransplanted s.c. (BSp6AS), susceptibility to NK cells and macrophages was further decreased, in the sense that all clones of the BSp6AS variant became resistant. Furthermore, the BSp6AS variant had lost some of the tumor-associated antigens (TAAs) found on BSp6S and A variants. More important, upon s.c. transplantation BSp6AS regularly metastasized to the draining LN, contrary to BSp6S and BSp6A. When locally growing tumors were excised, rats implanted with BSp6AS frequently died with metastatic tumor burdens in LNs and lung, while other animals survived after excision of BSp6S or BSp6A. The data indicate a correlation between resistance to lysis, morphology and metastatic capacity. But the initial loss of susceptibility to NK cells and macrophages during adaptation to ascitic growth, which can be considered as an escape mechanism, was not accompanied by increased metastatic capacity. Hence, we suppose that with respect to metastatic progression of the BSp6AS variant, resistance to lysis by loss of binding structures represents only a secondary, but not a causative, element.

Animals↗

PubMed1986

Cytotoxic T-cell precursors against non-immunogenic rat tumors: limiting dilution analysis.

After in vitro stimulation of lymphocytes with syngeneic tumor cells in the presence of interleukin 2 (IL-2), a cytotoxic T-cell response was observed against these spontaneously arising BDX tumors, which are non-immunogenic in the syngeneic host. The response was due to cytotoxic T-cells (CTL), which were specific for syngeneic tumor cells, i.e. neither syngeneic lymphoblasts, allogeneic lymphoblasts, allogeneic tumor cells, nor NK targets were lysed. The frequencies of anti-tumor lymph-node (LN) and spleen CTL precursors (CTLp) against a panel of syngeneic tumors of different histology varied between 1/6,000 and 1/16,000. Further analysis of the reactivity pattern of anti-tumor CTL revealed some degree of cross-reactivity within the syngeneic system. By a limiting dilution (LD) split culture approach in combination with cold target (CT) inhibition, it could be shown that tumors carry a panel of tumor-associated antigens (TAAs). Some tumors express individually specific as well as cross-reactive TAAs, while others carry cross-reactive TAAs only.

Animals↗

PubMed1986

Cell configuration and adhesive properties of metastasizing and non-metastasizing BSp73 rat adenocarcinoma cells.

The pattern of cell substrate interaction, the cell surface composition and the organization of cytoskeletal elements was studied in tumour cell variants of the BSp73 rat adenocarcinoma displaying different metastatic capabilities and cell configuration. The non-metastasizing AS variant cells adhered to the substrate and spread via vinculin-containing focal contacts. These cells also synthesized, secreted and assembled fibronectin at the pericellular area. The metastasizing ASML variant cells adhered to the substrate at a slower rate via thick cytoplasmic protrusions, but were removed from the substrate by trypsin-EDTA slower than the non-metastasizing AS variant cells. The ASML cells also synthesized very low levels of both vinculin and fibronectin, displayed a diffuse pattern of actin and tubulin organization, and were unable to spread on the substrate. Spreading could not be induced in the ASML cells by seeding the cells on an extracellular matrix derived from bovine corneal endothelial cells or on concanavalin A (conA)-coated substrates, or by the addition of db-cAMP to the medium. The metastasizing cells expressed a unique and abundant cell surface glycoprotein of Mr 170 000 which was also shed into the growth medium. The relationships among the adhesive properties, the organization of cell surface components and of the cytoskeleton in the tumour cell variants, and the expression of their metastatic phenotype is discussed.

Actins↗

PubMed1986

Influence of a minor recurrent idiotype on the regulation of immune response: route dependence.

Sp6, a BALB/c hybridoma, produces anti-TNP IgM antibodies (AB), which carry a minor recurrent idiotype (ID). Despite the fact that only about 20% of BALB/c anti-TNP AB carry the Sp6 ID, injection of Sp6-coated spleen cells (Sp6-SC) significantly influenced the anti-TNP B cell response. Repeated intratrail (i.t.) or intravenous (i.v.) injections of Sp6-SC resulted only in a minor increase of the anti-TNP background response. When mice consecutively were challenged with TNP-horse red blood cells (HRBC), i.t. injections of Sp6-SC resulted in a 2-3-fold increase in the number of anti-TNP plaque-forming cells (PFC), while i.v. injection of Sp6-SC displayed no effect on a primary anti-TNP response. But, after i.v. as well as i.t. application of Sp6-SC, it was not possible to obtain hapten-specific suppression by i.v. injection of TNP-haptenized lymphocytes. In vitro characterization of the underlying mechanism revealed that the helper effect, which only was observed after i.t. injection, was due to a Lyt-1+ population, not adhering to Sp6-coated plates, while counterregulation of hapten-specific suppression was found in a Lyt-2+ population, adhering to Sp6-coated plates. Hence, depending on the route of priming, injection of AB with a recurrent ID can augment the response towards the nominal antigen either directly via activation of helper cells or indirectly via activation of counterregulatory cells.

Animals↗

PubMed1986

Comparison of hapten-specific cytotoxic and suppressor T cells by a split culture approach.

The protocols for the induction of hapten-specific suppressor T cells (Ts) and hapten-specific cytotoxic T cells (Tc) are essentially the same. Hence, to exclude or support the possibility of an apparent suppression of B-cell responsiveness by elimination of B cells due to cytotoxic cells, limiting dilution cultures were concomitantly tested for suppression of a primary B-cell response against trinitrophenol (TNP), and cytotoxic activity towards a TNP-haptenized anti-TNP IgM hybridoma. When compared with the spleen cells (SC) of untreated Balb/c mice, the frequency of Tc was found to be increased after in vivo or in vitro induction of TNP-specific Ts (via intravenous injection of TNP-haptenized lymphocytes or cocultivation of SC with haptenized lymphocytes). Despite this synchronous increase of hapten-specific Ts and Tc, the number of wells displaying both cytotoxic and suppressive activity did not exceed the number of wells that were expected to contain Ts and Tc. Hence, in the system described, hapten-specific Tc did not lyse anti-hapten antibody-producing B cells to any measurable extent, and suppression of a B-cell response by in vivo or in vitro-induced Ts was independent of cytotoxic T-cell activity.

Animals↗

PubMed1986

Differential expression of intermediate filament proteins in metastatic and nonmetastatic variants of the BSp73 tumor.

The pattern of intermediate filament protein expression was studied in tumor cell variants of the BSp73 spontaneous rat adenocarcinoma of the pancreas exhibiting distinct morphology and metastatic phenotype. The non-metastasizing AS cells which adhere and spread on a solid substrate express only the vimentin type mesenchymal intermediate filament protein. The ASML metastatic cell variant which adheres but does not spread on the substrate expresses a complex pattern of cytokeratins characteristic of the adenocarcinoma of the pancreas and a low level of vimentin. The differences in the expression of the intermediate filament proteins between the variants were also reflected at the level of the corresponding mRNAs as revealed by RNA blot analysis with complementary DNA clones specific to vimentin and the acidic as well as the basic cytokeratin subfamily. When the two cell variants were cultured for 72 h in suspension culture on nonadhesive substrata the AS cells responded with a marked reduction in their vimentin synthesis. The ASML variant cells which are characterized by a round configuration in both monolayer and suspension culture continue to synthesize the same intermediate filament proteins under both culture conditions. The relationships among environmental conditions that affect cell shape and contacts, the shifts in the expression of intermediate filaments, and the metastatic property of tumor cells are discussed.

Adenocarcinoma↗

PubMed1985

Oscillation of antibody production and regulatory T cells in response to antigenic stimulation.

Priming with the T-dependent antigen trinitrophenylated horse red blood cells led to an oscillatory response of plaque-forming cells (PFC) with peaks of response after 4, 8, 12 and 16 days. Limiting dilution (LD) analysis of regulatory T cells indicated that the response is partly due to activation of helper T cells (Th), but mainly is the result of release from suppression by activation of a third regulatory T cell (T3) population (Zöller, H. and Andrighetto, G., Immunology 1985. 55: 703). Priming resulted in consecutive activation of suppressor T cells (Ts; day 1-3), a population regulating Ts (T3; day 2-4) and of Th (day 4). Furthermore, regulatory elements displayed a cyclical behavior like PFC. Th and T3 oscillated within a period of 4 days in phase with PFC, while Ts oscillated phase-shifted to PFC, Th and T3. Hence, oscillation of PFC after priming with a T-dependent antigen is the result of interactions among regulatory T cells. The data are interpreted as follows. Th are the primum movens of the oscillatory behavior of PFC response, since Th oscillate in phase with PFC and display the same pattern of decreasing amplitudes as PFC. However, the basic regulatory elements are Ts and T3 which are interlinked and oscillate phase shifted. As revealed by the time-course analysis of LD curves, T3 function as suppressor cells for Ts. Hence the status of mutual interactions of Ts and T3 determines suppression of Th or release from suppression, i.e. when T3 are found at high frequencies, Th are released from suppression, since T3 suppresses Ts. Instead, the increase in the frequency of Ts and their predation on Th determine the decrease of the frequency of Th. Thus, these data support the hypothesis of a circular network, the central regulatory core being composed of two elements, Ts and T3, with mutual suppressive activity.

Animals↗

PubMed1985

Evaluation of in vivo and in vitro effectivity of immune defense against a spontaneously arising, nonlymphoid rat tumor. I. Analysis of natural immune defense.

Possible mechanisms of natural defense against a nonimmunogenic, nonlymphoid rat tumor were evaluated in vitro and examined for effectivity in vivo, using BSp6S, the subcutaneously grown transplantation line of a spontaneously arising fibrosarcoma in the BDX rat strain, which is highly susceptible to natural killer (NK) cells and macrophages (Mø). The role of nonspecific immune defense in vivo was demonstrated by eliminating NK cells by irradiation and Mø by silica treatment. Especially after depletion of NK cells a significant acceleration of tumor growth and a reduction in the number of cells required for tumor takes was observed. Activation of Mø by Corynebacterium parvum (CP) did lead to retardation of tumor growth; prevention of tumor growth was only achieved after inoculation of a marginal dose of tumor cells. Activation of NK cells was of minor influence. It is concluded that NK cells and Mø are the main influences on survival time, the effectiveness of NK cells being limited to early periods of tumor growth.

Animals↗

PubMed1985

Evaluation of in vivo and in vitro effectivity of immune defense against a spontaneously arising, nonlymphoid rat tumor. II. T cell response after induction of immunogenicity.

It was evaluated in vitro whether it is possible to induce immunogenicity by haptenization of a nonlymphoid rat tumor, BSp6AS, which is known to be antigenic, but non-immunogenic, in the syngeneic host. The effectivity of 'induced immunogenicity' was tested in vivo. BSp6AS, an NK- and macrophage-resistant variant of a spontaneously arising fibrosarcoma in the BDX rat strain, does not induce a primary or a secondary T cell response after in vivo or in vitro priming. This deficiency in cytotoxic response is due solely to failure of activation of helper T cells (TH), since (a) cytotoxic T cells (CTL) can be detected after in vitro stimulation in the presence of interleukin 2 (IL-2)-containing medium; and (b) there are no indications for down-regulation of a potential specific immune response by suppressor T cells (TS). The lack of activation of tumor-specific TH can be bypassed by activation of hapten-specific TH. Upon coculture with haptenized tumor cells as a stimulator population, both hapten-specific and tumor-specific CTL are activated by hapten-specific TH. In line with the findings in vitro, no transplant rejection of naive tumor cells was seen after a variety of immunization schedules. But immunized F1 hybrids did reject tumor grafts, supporting the hypothesis of lacking help in the syngeneic situation. This could be confirmed in the syngeneic system by adoptive transfer experiments. Tumor-specific CTL, educated in vitro in the presence of IL-2, were ineffective. But complete protection against haptenized, and partial protection against native tumor cells was achieved in the additional presence of hapten-specific TH. To our knowledge these experiments prove for the first time that hapten-specific TH are efficient in inducing an immune response even against a nonlymphoid, nonimmunogenic tumor, i.e., it is possible (a) to activate tumor-specific CTL and (b) to initiate tumor graft rejection via hapten-specific TH.

Animals↗

PubMed1985

Time course analysis of regulation of cytotoxic T cells.

The frequency of cytotoxic T-cell precursors (T(K] was determined in spleen cells (SC) of naive mice and after subcutaneous (sc) or intravenous (iv) priming with trinitrophenyl (TNP)-haptenized syngeneic thymocytes by limiting dilution (LD) analysis in cultures containing exogenous interleukin 2 (IL-2). The frequency of TNP-specific T(K) (T(K)TNP) was found to be 1/4500 +/- 1097 in SC of naive mice. After treatment, the frequency of T(K)TNP increased up to threefold. An evaluation of regulatory elements (helper and suppressor T cells) (TH, TS) was possible by comparing SC from naive and primed animals after prolonged in vitro culture periods in the absence of exogenous IL-2. The experiments indicated that after 7 days of culture, activation of T(K) was limited by the supply of help. After 2-3 weeks of culture, sufficient help was available, especially in SC populations of primed mice, i.e., priming resulted in activation of the helper compartment with gradual differences depending on the route of priming (sc priming was more efficient than iv priming). But, after prolonged culture periods, cytotoxic activity was counterregulated by TS in naive and primed animals. While sc priming was a minor influence on the suppressor compartment, iv priming led to activation and numerical increase of TS. Finally, the activation status of effector and regulatory cells was tested at various times after antigenic stimulation. Four to five weeks after in vivo priming the system was found to move back into a status similar to that of naive mice, except that a small population of "nonsuppressible" T(K) appeared.

Animals↗

PubMed1985

Functional characterization of hapten-specific suppressor cells.

T cells from animals suppressed against a given hapten, trinitrophenyl (TNP), were analysed for their capacity to inhibit the humoral B-cell response against the hapten and/or a complex antigen, horse erythrocytes (HRBC), coupled or not to the hapten. As expected, suppression of the response to HRBC in all experiments required coupling to TNP. However, the suppressing capacity of the T cells varied with the stage of the B cells, with no detectable suppression occurring if already primed carrier-specific B cells were used. Hapten-specific T helper cells could, however, be induced in hapten-suppressed mice, when hapten-carrier conjugates were used as immunogen. Under these conditions normal efficiency of induction of carrier-specific T helper cells was observed, and this probably also applied to hapten-specific T helper cells to the same extent. This assumption was strengthened by using the hapten-binding capacity of the suppressor T cells and Lyt-1/2-specific sera to subdivide physically helper and suppressor function.

Animals↗

PubMed1985

Limiting dilution analysis of the frequencies of helper and suppressor T cells in untreated and TNP-treated BALB/c mice: response as a consequence of perturbation of a stable steady state.

B-cell response and suppression of response were analysed with respect to changes in frequency or composition of regulatory elements in comparison to untreated BALB/c mice. As antigenic stimulus the hapten TNP was used. Suppression was induced by intravenous (i.v.) injection of TNP-haptenized syngeneic lymphocytes; for inducing response, mice received TNP-horse red blood cells (HRBC). As the read-out system, plaque-forming cells (PFC) were determined after either the addition of naive B cells only [determination of the frequency of helper T-cells (TH)], or the addition of naive B cells plus saturating doses of TNP-specific TH [determination of the frequency of suppressor T-cells (Ts)]. The data indicate that, in untreated animals, a network of help and suppression is pre-existing, wherein TH are more frequent (1/1471) than TS (1/4413), but TS are dominant, i.e. when the fraction of non-responding cultures (F0) (determination of help) was plotted, an inversion of the curve was seen at high numbers of cells per well; however, the fractions of responding cultures (F+) (determination of suppression) could be plotted on a straight line. Application of antigen in suppressogenic or immunogenic form resulted in a two- to four-fold increase in the corresponding regulatory population but, concomitantly, a minor increase in the frequency of the mutual counteracting population was observed. Irrespective of any immunization schedule, TH were more frequent than TS. The overall shape of the 'helper' and 'suppressor' curves with spleen cells (SC) from suppressed mice resembled--besides changes in the frequencies--those obtained with SC of untreated animals. This corresponds to the maintenance of a state of unresponsiveness as in untreated animals. However, when SC from primed or suppressed plus primed mice were analysed, a different type of curve was obtained. Suppressor curves no longer followed a ratio dominance model; instead, at high numbers of cells per well, the frequency of wells with suppressive activity decreased. Correspondingly, in helper curves, a second slope of increasing numbers of wells with helper activity was seen at a high input of cells. Hence, response cannot be explained solely by expansion/activation of TH, but obviously a third regulatory population is involved which could not be detected in untreated animals. This third regulatory population could either be non-suppressible TH or--more likely, as will be discussed--contrasuppressor cells.

Animals↗