Epicutaneous immunization with protein antigen TNP-Ig alleviates TNBS-induced colitis in mice

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory autoimmune disease with limited treatment modalities. The animal model of colitis induced by treatment with trinitrobenzene sulfonic acid (TNBS-colitis) is commonly used to test new therapies of this disease. In our previous work we found that epicutaneous (EC) immunization with protein antigen induced a state of profound immunosuppression that inhibited inflammatory response in contact sensitivity, in experimental autoimmune encephalomyelitis (EAE) and in allogeneic skin graft rejection.

METHODS

TNBS-induced colitis was used as an experimental model.

RESULTS

In our current work, we showed that EC immunization with TNP-conjugated mouse immunoglobulin (TNP-Ig) prior to induction of TNBS-colitis alleviates disease severity what was determined by the body weight, the length and the weight of the colon, the histological activity index (HAI) and myeloperoxidase activity (MPO). Observed amelioration of the disease in TNP-Ig patched mice was accompanied with decreased production of IFN-γ and IL-17A by splenocytes. Additionally, spleen cells isolated from mice EC immunized with TNP-Ig prior to colitis induction showed increased production of IL-10 suggesting that this cytokine might be involved in inhibiting inflammatory response in the colon.

CONCLUSION

This work shows that EC immunization with protein antigen prior to TNBS-colitis induction ameliorates disease and observed suppression of inflammatory response in the colon might be mediated by IL-10.

IgE Enhances Antibody and T Cell Responses In Vivo via CD23+ B Cells

IgE Abs, passively administered together with their specific Ag, can enhance the production of Abs recognizing this Ag by >100-fold. IgE-mediated feedback enhancement requires the low affinity receptor for IgE, CD23. One possible mechanism is that B cells take up IgE-Ag via CD23 and efficiently present Ag to Th cells, resulting in better Ab responses. To test whether IgE Abs have an effect on Th cells in vivo, mice were adoptively transferred with CD4+ T cells expressing a transgenic OVA-specific TCR, before immunization with IgE anti-TNP (2,4,6-trinitrophenyl) plus OVA-TNP or with OVA-TNP alone. IgE induced a 6- to 21-fold increase in the number of OVA-specific T cells. These cells acquired an activated phenotype and were visible in splenic T cell zones. The T cell response peaked 3 days after immunization and preceded the OVA-specific Ab response by a few days. Transfer of CD23+ B cells to CD23-deficient mice rescued their ability to respond to IgE-Ag. Interestingly, in this situation also CD23-negative B cells produce enhanced levels of OVA-specific Abs. The data are compatible with the Ag presentation model and suggest that B cells can take up Ag via "unspecific" receptors and activate naive T cells in vivo.

Catalposide, a compound isolated from catalpa ovata, attenuates induction of intestinal epithelial proinflammatory gene expression and reduces the severity of trinitrobenzene sulfonic Acid-induced colitis in mice

Certain irinoid-producing plants have been used as herbal anti-inflammatory remedies. Here we evaluated whether catalposide (CATP), a single compound isolated from irinoid-producing plant Catalpa ovata, has a potential for preventing or ameliorating diseases characterized by mucosal inflammation. Preliminary microarray-based gene expression test revealed that CATP, which alone did not significantly affect expression of any of the >8,000 genes analyzed, attenuated the expression of tumor necrosis factor-alpha (TNF-alpha)-induced proinflammatory genes including interleukin-8 (IL-8) in human intestinal epithelial HT-29 cells. Down-regulation of IL-8 mRNA accumulation was also reflected by the decreased IL-8 secretion in CATP-treated HT-29 cells. The signal transduction study revealed that CATP significantly attenuates TNF-alpha-mediated p38 and extracellular signal-regulated kinase (ERK) phosphorylation. Further, CATP reduced NF-kappaB-mediated transcriptional activation as well as Ikappa-Balpha degradation. To establish the in vivo relevance of these findings, we examined whether CATP could affect intestinal inflammation in vivo using the mouse model of trinitrobenzene sulfonic acid (TNBS)-induced inflammatory colitis. Intrarectal administration of CATP dramatically reduced the weight loss, colonic damage, and mucosal ulceration that characterize TNBS colitis. Moreover, CATP suppressed the expression of TNF-alpha, interleukin-1beta, and intercellular adhesion molecule-1 along with the inhibition of NF-kappa B p65 translocation into nucleus in TNBS colitis. Collectively, current results demonstrate that CATP may be an effective agent for the treatment of diseases characterized by mucosal inflammation.

Granulocyte-Macrophage Colony-Stimulating Factor-Based Melanoma Cell Vaccines Immunize Syngeneic and Allogeneic Recipients via Host Dendritic Cells

Subcutaneous injection of GM-CSF-expressing cancer cells into experimental animals results in protective cancer immunity. To delineate the mode of action of such vaccines, we used trinitrophenyl, the antigenic moiety of the contact allergen trinitrochlorobenzene, as surrogate Ag. Trinitrophenyl-derivatized bone marrow-derived dendritic cells were found to elicit a contact hypersensitivity response in syngeneic, but not in allogeneic recipients, compatible with their expected mode of direct Ag presentation. When expressing GM-CSF, haptenized M3 melanoma cells were also able to induce a contact hypersensitivity response but, in contrast to bone marrow-derived dendritic cells, not only in syngeneic but also in allogeneic recipients. This argues for a critical role of host APC. To identify their nature, we introduced the beta-galactosidase (betagal) gene into M3-GM cells. Their administration activated betagal-specific, L(d)-restricted CTL in syngeneic BALB/c mice. Evaluation of lymph nodes draining M3-GM-betagal injection sites revealed the presence of cells presenting the respective L(d)-binding betagal peptide epitope. Based on their capacity to activate betagal-specific CTL, they were identified as being CD11c(+) dendritic cells. These experiments provide a rational basis for the use of GM-CSF-based melanoma cell vaccines in an allogeneic setting.

IKK beta is required for peripheral B cell survival and proliferation

NF-kappaB activity in mammalian cells is regulated through the IkappaB kinase (IKK) complex, consisting of two catalytic subunits (IKKalpha and IKKbeta) and a regulatory subunit (IKKgamma). Targeted deletion of Ikkbeta results in early embryonic lethality, thus complicating the examination of IKKbeta function in adult tissues. Here we describe the role of IKKbeta in B lymphocytes made possible by generation of a mouse strain that expresses a conditional Ikkbeta allele. We find that the loss of IKKbeta results in a dramatic reduction in all peripheral B cell subsets due to associated defects in cell survival. IKKbeta-deficient B cells are also impaired in mitogenic responses to LPS, anti-CD40, and anti-IgM, indicating a general defect in the ability to activate the canonical NF-kappaB signaling pathway. These findings are consistent with a failure to mount effective Ab responses to T cell-dependent and independent Ags. Thus, IKKbeta provides a requisite role in B cell activation and maintenance and thus is a key determinant of humoral immunity.

Chronic toxicity of 1,3,5-trinitrobenzene in Fischer 344 rats

The chronic toxicity of 1,3,5-trinitrobenzene (TNB) in male and female Fischer 344 (F344) rats was evaluated by feeding a diet containing 0, 5, 60, and 300 ppm of TNB for 2 years. The calculated average TNB intake over 2 years for males and females was 0.22, 2.64, 13.44 and 0.23, 2.68, 13.31 mg/kg body weight (BW)/day respectively. Terminal body weights were decreased and water intake was increased in both sexes (300 ppm), whereas food consumption was decreased in males (60 and 300 ppm groups) only. The relative spleen weights were significantly decreased in both sexes (300 ppm), whereas the relative brain weights were increased in females only (300 ppm). Hematological effects were not observed in animals killed at the 2-year time point, except significant decrease in the mean corpuscular hemoglobin (MCH) in males (300 ppm) and in females (60 and 300 ppm). Methemoglobin levels were increased in both sexes in the high dose group. Histopathological examination showed treatment-related changes in the kidney (hyaline droplets; 60 and 300 ppm) and the spleen (erythroid cell hyperplasia and pigment deposition; 300 ppm) of both sexes. Cytoplasmic hyaline droplets in the kidneys were characterized by immunohistochemistry as alpha-2mu-globulin. We propose a chronic, oral no-observable-adverse-effect level (NOAEL) of 2.68 mg/kg BW/day for TNB in the rat, based on the hematological and renal changes.

Cross-reactivity of TNP immune effector T cells that mediate contact hypersensitivity and inflammatory bowel disease in the mouse

BACKGROUND

Experiments were aimed to test the cross-reactivity of immune Th1 cells that mediate contact hypersensitivity (CHS) or inflammatory bowel disease (IBD) to TNP in the mouse.

METHODS

CBA/J mice were immunized either epicutaneously or intrarectally with TNP and after appropriate time intervals were challenged with antigen in a crossed manner. The CHS reaction was measured by the ear swelling test. IBD was quantified by increase of colon weight and myeloperoxidase level. Both reactions were confirmed histologically. In passive-transfer experiments, mesenteric lymph node cells of animals sensitized intrarectally and peripheral lymph node and spleen cells of mice immunized epicutaneously were used. In some experiments, before being immunized mice were made either unresponsive to the TNP hapten by induction of suppressor T cells, or resistant to suppression after induction of upregulatory T cells.

RESULTS

Irrespective of the mode of sensitization upon appropriate challenge with antigen all mice developed a good CHS reaction as well as significant IBD. This cross-reactivity could be passively transferred by immune cells. In mice in which antigen-specific down- or upregulatory cells were induced before sensitization both CHS and IBD to TNP were modulated accordingly.

CONCLUSION

TNP hapten deposited on skin or on mucosal surfaces induces effector cells that recognize antigen independent of its tissue localization, and produce a local inflammatory reaction. TNP-specific up- and downregulatory cells, shown before to regulate the CHS reaction, similarly modulate the generation and development of hapten-induced IBD.

Chronic oral antigen exposure induces lymphocyte migration in anaphylactic mouse intestine

Persistent diarrhea, vomiting, and dehydration are symptoms often seen in patients suffering from food allergy after chronic antigen exposure; however, the precise mechanisms involved have not been well defined. In an effort to clarify the mechanisms of the chronic intestinal changes attributable to genuine IgE-mediated anaphylactic reactions induced by orally administered antigen, a mouse model was established by s.c. implantation of a murine hybridoma capable of producing monoclonal anti-trinitrophenyl IgE antibody, and the morphologic and immunologic changes occurring in the intestine upon chronic antigen exposure were investigated. In the early stage after ingestion of the antigen, diarrhea and noticeable infiltration of mast cells as well as eosinophils into the lamina propria were observed. A substantial increase in serum histamine levels as well as an increase in leukotriene C4 synthesis in the jejunal mucosa were observed 1 h after antigen challenge. Also, the synthesis of leukotriene B4 was significantly elevated for up to 9 h after antigen challenge. The expression of both intercellular adhesion molecule-1 (ICAM-1) on mucosal vascular endothelial cells and IAd on epithelial cells was markedly enhanced, and noticeable infiltration of eosinophils and lymphocytes was also confirmed in the mouse model after chronic antigen exposure. These findings suggest that oral antigen exposure induces anaphylactic reactions in the intestine mediated by mast cells and eosinophils in response to the IgE-antigen complex in the early phase, and also induces lymphocyte migration after chronic antigen exposure.

Impaired antibody responses in H-2Ab mice

In murine in vivo systems, Ags administered in physiologic solutions together with specific IgE induce a significantly higher Ab response than Ags administered alone. In vitro, IgE in complex with Ag enhances B cell-mediated presentation of the Ag to T cells. Both phenomena require an intact low affinity receptor for IgE (Fc epsilon RII/CD23), suggesting that the effect on in vivo Ab responses is caused by increased Ag presentation. We here show that mice carrying the MHC class II Ab molecule (e.g., C57BL/6 and 129/Sv) do not produce Abs to BSA when immunized with BSA-2,4,6-trinitrophenyl (TNP) in complex with monoclonal IgE anti-TNP. In contrast, strains of all other MHC haplotypes tested (H-2d, H-2k, H-2p, H-2q, and H-2s) respond vigorously to IgE/BSA-TNP complexes, with Ab responses several hundred-fold higher than the responses in H-2b mice. C57BL/6 mice were unable to produce a carrier-specific response also after immunization with IgE/OVA-TNP, IgE/diphtheria toxoid-TNP, or IgE/tetanus toxoid-TNP. Although the low responsiveness mapped to the Ab region, responsiveness was not restored in C57BL/6 mice carrying transgenic Ak, suggesting that a nonclassical A-region-encoded gene product is involved. Most importantly, our data call attention to the fact that the C57BL/6 and 129 mouse strains, which are widely used for producing transgenic animals, have defective immune responses.

Metabolism of explosive compounds by sulfate-reducing bacteria

The metabolism of various explosive compounds-1,3,5-trinitrobenzene (TNB), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX)-by a sulfate-reducing bacterial consortium, Desulfovibrio spp., was studied. The results indicated that the Desulfovibrio spp. used all of the explosive compounds studied as their sole source of nitrogen for growth. The concentrations of TNB, RDX, and HMX in the culture media dropped to below the detection limit (<0.5 ppm) within 18 days of incubation. We also observed the production of ammonia from the nitro groups of the explosive compounds in the culture media. This ammonia served as a nitrogen source for the bacterial growth, and the concentration of ammonia later dropped to <0.5 mg/L. The sulfate-reducing bacteria may be useful in the anaerobic treatment of explosives-contaminated soil.

Selective immunomodulation by the autoimmunity-inducing xenobiotics streptozotocin and HgCl2

Exposure to certain drugs and environmental chemicals can provoke the onset of autoimmune disease in susceptible individuals by releasing (self) epitopes for which tolerance has not been established, while simultaneously providing the necessary adjuvant activity. The resulting response type is influenced by the genotype of exposed individuals and relates to susceptibility to the adverse immune effects of the chemicals. Here, we assessed the modulatory role of the chemical compounds themselves. A single injection of streptozotocin (STZ) increased the number of CD8+ cells, macrophages, apoptotic cells, and IFN-gamma-producing T helper and T cytotoxic cells, whereas the number of CD4+ cells and B cells was reduced in the draining lymph node. Coinjection with the reporter antigen TNP-OVA resulted in primary and secondary production of TNP-specific antibodies that were predominantly of IgG2a and IgG2b isotype, whereas STZ did not enhance priming for delayed-type hypersensitivity (DTH) responses to TNP-OVA. Injection of HgCl2 on the other hand, reduced the number of IFN-gamma-producing cells, induced accumulation of B cells and CD4+ and CD8+ T cells, enhanced IgG1 and IgE production to TNP-OVA, and primed for secondary IgG1 and IgE production as well as for DTH reactions. Together these results indicate that a single injection of STZ stimulates type-1 responses, whereas HgCl2 enhanced mixed type-1 and -2 responses in BALB/c mice. These response types match the (auto)immune effects elicited to unknown (auto)antigens following multiple injections of these chemicals.

Direct thymic involvement in anterior chamber-associated immune deviation: evidence for a nondeletional mechanism of centrally induced tolerance to extrathymic antigens in adult mice

Recent reports have suggested that the dichotomy between central (thymic) and peripheral T cell tolerance is not absolute and that self-tolerance in perinatal animals may also involve the intrathymic generation and release to the periphery of Ag-specific immunoregulatory T cells. We have expanded this concept to include tolerance to non self Ags administered extrathymically to adult animals. In this study, we use the anterior chamber-associated immune deviation (ACAID) to demonstrate that central regulation of acquired peripheral tolerance can be induced in adult mice by the intraocular administration of low doses of nonself Ag. The results show that adult thymectomy prevents the inhibition of trinitrophenol (TNP)-specific delayed-type hypersensitivity, which normally occurs after injection of TNP-BSA into the anterior chamber (AC) of the eye. Thymocytes obtained from mice 1 to 3 days, but not 5 to 7 days, after AC injection of TNP-BSA or BSA alone specifically transfer inhibition of delayed-type hypersensitivity to mice primed with the homologous Ag. The latter observation, when correlated with the time of onset of ACAID, suggests that immunoregulatory T cells are formed in the thymus within 24 h and are exported to the peripheral lymphoid tissues between 2 and 5 days after AC injection of Ag. Immunomagnetic separation of thymocytes revealed that the immunoregulatory activity resides within the minor subset of CD4-, CD8-, TCR-alphabeta+ cells, previously postulated to induce fas ligand-mediated apoptosis and Th1 to Th2 immune deviation. Hence, the present study identifies ACAID as a prototypical model of centrally induced, nondeletional tolerance to extrathymic nonself Ags.

1,3,5-Trinitrobenzene-induced encephalopathy in male Fischer-344 rats

Administration of 1,3,5-trinitrobenzene (TNB) to male Fischer-344 rats produced ataxia after 6 or 7 oral doses (71 mg/kg). Light microscopic examination after 10 days revealed petechial hemorrhages in the brain stem and cerebellum and bilaterally symmetric degeneration and necrosis (malacia) with reactive gliosis in the cerebellar peduncles. The malacia was dorsal and lateral to the fourth ventricle involving the cerebellar nuclei, medial and lateral vestibular nuclei, and inferior colliculi. Blood vessels associated with the lesion had widened Virchow-Robin spaces, occasionally with extravasated erythrocytes. Rats administered daily oral doses of 35.5 mg/kg of TNB for 10 days and 35.5 and 71 mg/kg of TNB for 1 or 4 days did not have brain lesions.

Neonatal suppression with anti-Ia antibody. III. In vivo responses to the type 2 antigen TNP-Ficoll

We studied the response to thymus-independent type 2 (type 2) Ag in mice suppressed from birth with anti-Ia antibody. Although these mice have significantly reduced numbers of surface IgM+ cells and reduced or absent levels of Ia-restricted Th cell activity, their IgM antibody response to the type 2 Ag TNP-Ficoll was unaffected whereas that to the prototypic thymus-dependent Ag SRBC was predictably eliminated. These data suggest that an in vivo antibody response can be made to type 2 Ag in the absence of Ia-dependent cellular interactions. The surface IgM+IgD-Ia- B cells that are found in the anti-Ia antibody-suppressed mouse may represent an expanded population of Ia-independent, type 2 Ag-sensitive B cells normally present as a smaller proportion of the splenic lymphocyte population. Thymus-dependent responses, which have been shown to have an absolute requirement for an Ia-dependent interaction, are absent in these animals.

Recognition of idiotypic structures in the thymus

During the passage through the thymus, T cells are selected which recognize self major histocompatibility complex (MHC) antigens with low avidity. Whether the T-cell repertoire for recognition of altered self is also built up intrathymically or in the periphery, and whether it is determined exclusively by external antigens or is shaped by the internal environment is still a matter of debate. This question was addressed by analysing the responsiveness of thymocytes during post-natal development towards a nominal antigen [trinitrophenyl (TNP)] and an anti-TNP monoclonal antibody (Sp6), which carries a recurrent idiotype. During the first weeks of life, in vitro cultures of thymocytes proliferated strongly in the absence of nominal antigen. Proliferation rates were not increased by the addition of nominal antigen [TNP-ovalbumin (OA)], but a significant increase was noted in the presence of Sp6, thymocytes recognizing the processed immunoglobulin. After in vivo stimulation with TNP conjugates, 'antigen-specific' clones could also be detected in the thymus, the frequency of clones proliferating in response to Sp6 being further augmented. With increasing age, the proliferative capacity of thymocytes from unstimulated and antigenically stimulated mice decreased significantly. Responsiveness of spleen cells (SC) differed in some respects. The response towards Sp6 decreased with age, while antigen-specific clones were detected at increasing frequencies during post-natal development. Furthermore, after antigenic stimulation, the frequency solely of antigen-specific, but not of Sp6-specific clones was increased. Thus, it appears that the T-cell repertoire is shaped already during the intrathymic passage, being influenced primarily by the B-cell repertoire and modulated further by external antigen.

Primary in situ immune response in popliteal lymph nodes and spleen of mice after subcutaneous immunization with thymus-dependent or thymus-independent (type 1 and 2) antigens

Mice were immunized subcutaneously with thymus-independent (TI)-type 1 antigen trinitrophenylated lipopolysaccharide (TNP-LPS), TI-type 2 antigen TNP-Ficoll or thymus-dependent (TD) antigen TNP-keyhole limpet haemocyanin (TNP-KLH) in order to study the primary in situ immune response in popliteal lymph nodes (PLN) and spleen. The spleen responded more rapidly in developing specific antibody-forming cells (AFC) than the lymph nodes did, in spite of the fact that antigens reach the spleen only after passing several lymph node stations. This difference between lymph nodes and spleen in developing AFC was particularly significant with respect to the responses to TI (both type 1 and type 2) antigens. No differences in the distribution of specific AFC in PLN and spleen were observed after immunization with TI and TD antigens. Results are discussed with respect to the relative contributions of lymph nodes and spleen to immune responses to antigens injected subcutaneously.

Suppressive effect of ultraviolet-B-irradiation of epidermal cells on the induction of contact sensitivity

Contact sensitivity to trinitrophenyl (TNP) hapten was induced by subcutaneous (s.c.) administration of TNP-modified syngeneic spleen cells or epidermal cells (EC) (TNP-EC). Intraperitoneal (i.p.) inoculation of TNP-EC resulted in a comparable response, whereas i.p. administration of TNP-spleen cells or TNP-modified-ultraviolet (UV)-preirradiated EC (TNP-UV-EC) failed to induce TNP-contact sensitivity responses. The present study investigates the effect of UV-irradiation on the potential of EC for inducing the contact sensitivity response. Exposure of BALB/c mouse EC in vitro to 1600 J/m2 of UV-B before they were modified with TNP had no discernible effect on the Ia-positivity and viability of EC. Coexistence of TNP-UV-EC had no inhibitory effect upon the contact sensitivity response induced by TNP-EC via the i.p. route. The absence of suppressor cell generation was substantiated by the adoptive transfer of spleen cells from mice administered TNP-UV-EC i.p. to normal syngeneic mice. The effect of interleukin 1 (IL-1) or epidermal cell-derived thymocyte-activating factor (ETAF) in restoring the ability of TNP-UV-EC to induce contact sensitivity was examined. IL-1 or ETAF administered along with TNP-spleen cells i.p. induced a potent contact sensitivity response, whereas the same preparations of IL-1 or ETAF were unable to restore the contact sensitivity induction by TNP-UV-EC. The results are discussed in the context of UV-induced cell surface changes of the Langerhans cell population.

Physiology of IgD. VI. Transfer of the immunoaugmenting effect of IgD with T delta-containing helper cell populations

We show that the IgD-induced augmentation of the immune response to trinitrophenylated keyhole limpet hemocyanin can be transferred to syngeneic mice with spleen cells from IgD-injected donors. The augmenting activity is present in the Lyt-1+2-, L3T4+ T cell population and is absent from B cells. The ability of transferred T cells to augment the immune response correlates with the presence of a high frequency of Lyt-1+2- T cells that form rosettes with IgD-coated sheep erythrocytes (T delta cells). Such rosette-forming cells can also be induced by incubation of spleen cells from normal donors in IgD-coated petri dishes. Injection of normal spleen cells exposed to IgD-coated petri dishes together with antigen also augments the immune response of recipients. The existence of a regulatory circuit based upon interactions between T delta cells, antigen, B cell surface IgD, and serum IgD, is proposed.

Elimination of trinitrophenol-specific antibody response by antigen-toxin conjugates

The aim of the experiments presented here is the selective inhibition of an antigen-specific immune response. Antigen receptors are used as targets for conjugates of antigens and toxin to eliminate antigen-reactive cells. The trinitrophenol (TNP)-specific immune response can be specifically abrogated by incubating the TNP-keyhole limpet haemocyanin (KLH)-primed spleen cells with TNP-ricin or TNP-chicken IgG-ricin conjugates before in vitro stimulation with TNP-KLH. The rate of elimination is dose-dependent and related to the degree of TNP moieties bound to the toxin molecule. The specificity of the toxin conjugates is demonstrated by treating sheep erythrocyte-primed spleen cells with TNP-IgG-ricin conjugates. These results may have therapeutic relevance for treating autoimmune diseases.

Immune memory expression to Tnp-Ficoll in CB.20 mice: evidence for a multigenic control

Trinitrophenyl (Tnp)-Ficoll, a class 2 thymus-independent (TI) antigen, generates in most mouse strains Tnp-specific B-memory cells which can be detected in situ 1 week after priming by a heterologous stimulation with Tnp-lipopolysaccharide (LPS) but not by a homologous Tnp-Ficoll challenge. We have investigated the secondary responses raised in CB.20 congenic mice by a homologous challenge in situ occurring at various time intervals after priming. We report that a memory-type response is obtained, culminating when the challenge is performed at 4 weeks; this finding assesses definitely the ability of TI-2 antigens to produce immunological memory under standard conditions. However, the same immunization procedure elicits no memory-type response in the majority of other mouse strains, suggesting a possible genetic control of the expression of memory to class 2 TI antigens. The utilization of F1 hybrids between C57BL/6 and BALB/c and of appropriate congenic strains shows indeed that this memory expression is under multigenic control: Igh-V or closely linked genes are clearly involved but a complementation with other gene(s), located outside the H-2 complex, is required for a memory-type response to Tnp-Ficoll. We have also analyzed the secondary heterologous response to Tnp-LPS in CB.20 mice at different times after Tnp-Ficoll priming. The difference in the kinetic profile of the heterologous (TI-2----TI-1) versus homologous (TI-2----TI-2) secondary responses is discussed in terms of B-memory-cell ontogeny and humoral regulation.

Suppression and contrasuppression in the induction of contact sensitivity by the administration of cellbound antigen-antibody complexes

The tolerogenic signal produced by the i.v. injection of haptenated peritoneal exudate cells can be converted to an immunogenic signal by treating the cells with antibody to the hapten before administration. We examined this phenomenon and found that immunity induced by antigen-antibody complexes, as opposed to skin sensitization, is resistant to suppressor T cell influences. This resistance to suppression is due to the activation of an I-J+, Ly-1 T cell population which adheres to the Vicia villosa lectin, all characteristics of contrasuppressor T cells. Because haptenated cells can induce immunity if injected subcutaneously or into cyclophosphamide-pretreated recipients (thereby avoiding the induction of suppressor cells), we suggest that the activation of contrasuppressor cells by antigen-antibody complexes overrides suppressive influences in the host, allowing immunity to become dominant. The possible roles of suppression and contrasuppression in channeling the effector arm of the immune response (e.g., contact sensitivity vs humoral immunity) are discussed.

Age-dependent isotype variation during secondary immune response in MRL/lpr mice producing autoanti-gamma-globulin antibodies

A profound inability to produce IgG anti-2,4,6-trinitrophenyl (TNP) antibodies during the secondary immune response elicited by a T-dependent antigen was observed in aged MLR/lpr mice. This unresponsiveness is associated with a significantly low indirect anti-TNP plaque-forming cell response and a weak in vitro anti-TNP response upon the culture of keyhole limpet hemocyanin-primed T cells and TNP-primed B cells in the presence of TNP. The markedly low IgG anti-TNP response observed in aged MLR/lpr mice cannot be related to the presence of rheumatoid factors which are observed during the secondary response, since MRL +/+ and 129/J mice, (non-autoimmune disease strains), also produce significant amounts of anti-gamma-globulin antibodies yet mount a strong IgG anti-TNP response.

Delayed maturation of the antibody response to type 2 thymus-independent antigens in a partially inbred strain of chicken

The ontogeny of antibody responses to trinitrophenylated (TNP) thymus-independent (TI) antigens was compared in two partially inbred strains of chicken: the SC strain (B2/B2 genotype) and the FP strain (B15/B22 genotype). In the SC chicken, maturation of both the splenic anti-TNP plaque-forming cell (PFC) response and the 19S hemagglutinating antibody response to TI type 2 (TI-2) antigens, TNP-Ficoll and TNP-dextran, were delayed to a significantly later time in ontogeny (20 wk of age) than in the FP chickens (9 wk of age). Four- to 6-wk-old SC chickens were virtually immunologically unresponsive to stimulation with TI-2 antigens. The TI-1 antigen TNP-Brucella abortus was equally immunogenic in both FP and SC chickens of different age groups tested. Kinetic studies of the primary PFC response to TNP-Ficoll in immunologically mature chickens of the SC and FP strains demonstrated a peak PFC response 4 days after antigen injection, followed by a rapid decline in numbers of splenic PFC/spleen on day 6. The results of these studies are discussed in relation to earlier observations that suggested there may be a delay or a defect in the ontogeny of the thymus in the SC chicken.

Production of auto-anti-idiotype antibody during the normal immune response. X. Response to TNP-Ficoll in the chicken

The spontaneous production of auto-anti-idiotype (Id) was demonstrated after injection of chickens with trinitrophenylated Ficoll (TNP-F) by: (a) the presence of hapten-augmentable plaque-forming cells (PFC), (b) the ability of serum and of hapten eluates from immune spleen cells to cause hapten-reversible inhibition of anti-TNP plaque formation, and (c) an enzyme-linked immunosorbent assay (ELISA). Tests for anti-Id using the ELISA and hapten-reversible inhibition of PFC correlated very well. As in the mouse, the incidence of hapten-augmentable PFC was reduced by thymectomy and increased by the transfer of TNP-F-immune spleen cells. Hapten-augmentable PFC were also observed during the immune response of chickens to p-azobenzene arsonate-conjugated Brucella abortus.

Production of auto-anti-idiotype antibody during the normal immune response. XI. Ficoll-induced variations in auto-anti-idiotype production during the response to 2,4,6-trinitrophenyl-Ficoll

The responses to 2,4,6-trinitrophenyl conjugates of different Ficoll preparations differ with respect to the magnitude of the accompanying auto-anti-idiotype (Id) response in both mice and chickens. Evidence is presented that reduced auto-anti-Id production in the chicken is due to the activation of suppressor activity by some preparations of Ficoll.

Selective effect of irradiation on responses to thymus-independent antigen

Low doses of ionizing radiation have a selective immunosuppressive effect on in vivo B cell responses to thymus-independent (TI) antigens. The B cell response, assayed as direct anti-trinitrophenyl (TNP)-specific plaque-forming cells (PFC), induced by type 2, TI antigens (TNP-Ficoll or TNP-Dextran), was reduced, on the average, by 10-fold in animals exposed to 200 rad of ionizing radiation 24 hr before antigen challenge. In contrast, PFC responses to type 1, TI antigens (TNP-lipopolysaccharide or TNP-Brucella abortus) are unaffected in mice exposed to the same dose of radiation. Adoptive transfers showed that this selective immunosuppression is a result of the specific inactivation of the B cell subpopulation responding to type 2, TI antigens. These experiments suggest that physiologic differences exist in the B cell subpopulations of normal mice which respond to type 1, or type 2, TI antigens.

Effects of deoxycoformycin in mice. I. Suppression and enhancement of in vivo antibody responses to thymus-dependent and -independent antigens

The effect of 2'-deoxycoformycin (DCF) on the PFC responses of AKR mice to SE, TNP-Ficoll, and TNP-B. abortus was examined. Subcutaneous injection of DCF 4 days before antigen caused suppression of all three responses by 70 to 78%. In contrast, injection of DCF 1 day after antigen caused enhancement of both the anti-SE and the anti-TNP-Ficoll responses. Although a single high dose of cortisone acetate injected 4 days before antigen caused a similar suppression, the effect of DCF was not mediated via a steroid release, inasmuch as DCF also suppressed the immune response in adrenalectomized mice. The response of BALB/c mice to TNP-Ficoll was also inhibited by DCF pretreatment and enhanced by injection of DCF after antigen. In contrast, in athymic mice DCF caused suppression of the anti-TNP-Ficoll PFC response, whether injected before or after antigen. These results are interpreted as suggesting that DCF causes suppression primarily via an effect on B cells. The enhancement seen in normal but not in athymic mice may possibly be ascribed to an effect on suppressor T cells. Apparently the enhancement of both TD and TI responses caused by DCF injected 1 day after antigen in normal mice is the net result of these two opposing effects. The results imply that helper T cells are resistant to DCF.

T cell regulation of immunoglobulin class expression in the B cell response to TNP-Ficoll: characterization of the T cell responsible for preferential enhancement of the IgG2a response

Syngeneic T cells injected into athymic nu/nu mice cause a preferential enhancement in the amount of IgG2a anti-TNP Ab produced by these mice to TNP-Ficoll. This enhancement appears to be caused by T cell effects on the IgG switching pathway. Through the use of F1----parent chimeras, the helper T cells were shown to affect TNP-Ficoll-responsive B cells in an H-2-unrestricted manner. The ability of T cells to mediate this IgG2a enhancement did not appear to be unique to any particular murine genetic background, because it was observed with T cells and nu/nu mice of C57BL/10, BALB/c, CBA/Ca, and B10.D2 strains. Priming of T cell donors with Ficoll or TNP-Ficoll did not increase the ability of splenic T cells, on a per cell basis, to enhance the IgG2a Ab response to TNP-Ficoll. The T cell population responsible for modulating the isotypic response was found to be sensitive to C-mediated cytotoxicity with both anti-Lyt-2 and anti-Lyt-1 hybridoma Ab. Although T cells from both the thymus and the spleen expressed enhancing activity, splenic T cells were more effective, on a per cell basis, than were thymocytes. The observations suggest that T cells that appear to enhance the switch to IgG2a in TNP-Ficoll-responsive B cells are not effectively primed by the antigen and interact with TNP-Ficoll-activated B cells through an H-2-unrestricted mechanism.

Enhanced TNP-reactive helper T cell activity and its utilization in the induction of amplified tumor immunity that results in tumor regression

The present study was designed to investigate the generation of trinitrophenyl (TNP)-reactive helper T cell activity potent enough to induce the regression of a syngeneic tumor; this occurs by augmenting antitumor-specific immunity through T-T cell interaction. Mice whose skin was painted with trinitrochlorobenzene (TNCB) exhibited a variety of anti-TNP T cell responses, including delayed-type hypersensitivity (DTH) and cytotoxic T cell responses, as well as helper T cell activity. Pretreatment of C3H/He mice with TNP-conjugated copolymer of D-glutamic acid and lysine (TNP-D-GL) or cyclophosphamide, which have been shown, respectively, to inactivate TNP-specific suppressor T cells or suppressor T cells in general, exhibited a slight or marginal augmentation of DTH and cytotoxic potentials when tested 5 wk after TNCB painting. In contrast, the same pretreatment regimens induced an appreciably amplified generation of anti-TNP helper T cell activity. This amplified TNP-helper T cell activity was demonstrated to enhance cytotoxic responses to antigens other than TNP in an antigen-nonspecific way. In fact, such helper T cells enhanced antitumor CTL responses when co-cultured with spleen cells from syngeneic X5563 plasmacytoma-bearing mice in the presence of TNBS-modified X5563 tumor cells. This amplified TNP-helper cell system was utilized for its immunotherapeutic potential. When TNCB was injected into X5563 tumor mass of syngeneic C3H/He mice in which the amplified TNP-helper T cell activity had been generated, an appreciable number of growing tumors was observed to regress. This contrasted with the low incidence of tumor regression observed in mice in which TNP-helper activity had been induced by TNCB painting without inactivation of suppressors. Thus, the present model provides an effective immunotherapeutic manipulation for eliciting enhanced in vivo tumor regression, and emphasizes a role of helper T cells in augmentation of syngeneic tumor immunity.

Relationship of germinal centers in lymphoid tissue to immunologic memory. VI. Transfer of B cell memory with lymph node cells fractionated according to their receptors for peanut agglutinin

We isolated germinal center B cells by exploiting their high affinity for peanut agglutinin (PNA). The PNA+ and PNA- B cells, fractionated by panning on PNA-coated petri dishes, were examined for their ability to transfer memory responses to irradiated recipients at various times after priming. With such fractionated B cells from lymph nodes taken at the peak of germinal center formation, the largest response was obtained in recipients of the PNA+ B cell population. At 4 to 5 wk after priming, and 10 days after challenge with an unrelated antigen, memory responses were approximately equal in recipients of PNA+ or PNA- B cells. At 14 wk after priming, memory responses were found only in recipients of the PNA- B cell population. Memory B cells from the spleen, taken from mice primed in the footpad 8 wk earlier, were also PNA-. Finally, we show that boosting with a TNP-conjugate in the footpad, 6 mo after priming in the same footpad, induced the reappearance of marked memory responsiveness in the PNA+ B cell fraction of the draining node.

The use of haptenated immunoglobulins to induce B cell tolerance in vitro. The roles of hapten density and the Fc portion of the immunoglobulin carrier

The relationship between the Fc region of trinitrophenylated (TNP)-immunoglobulins (Ig), and their ability to induce tolerance was examined. It was found that adult B cells responding to a T-independent (TI) antigen were tolerized by TNP11 human gamma globulin (HGG), but not by TNP10F(ab')2 fragments of HGG. Increasing the hapten density on the F(ab')2 fragments overcame their inability to induce tolerance. Thus, a TNP17-F(ab')2 was an effective tolerogen. Murine myeloma proteins of different IgG subclasses were similarly tested. A TNP12-IgG2a and a TNP11-IgG1 induced tolerance, whereas two TNP11-12-IgG3 did not. However, a more heavily haptenated TNP18-IgG3 was tolerogenic. These results suggest that lightly haptenated immunoglobulins depend upon Fc receptor binding to induce tolerance in adult B cells. Non-Fc receptor-binding carriers are not tolerogenic unless they are more heavily haptenated. Finally, T cell and macrophage depletion experiments suggest that the tolerogens act directly on the B cells.

Influence of lymphokines on the anti-TNP-Ficoll response of normal and X-linked B lymphocyte-defective mice

Immunodeficient CBA/N and F1 hybrids of CBA/N X SJL or DBA/2Ha mice were induced to make an antibody response to TNP-Ficoll by i.v. injections of lymphokines together with the antigen. The best responses (up to 12,000 PFC/spleen on day 4) were obtained by repeated i.v. lymphokine injections on days 0, 1, 2, and 3. Lymphokines obtained from PHA-stimulated LBRM-33 cells were less effective than those in supernatants (SN) from cocultures of SJL lymph node and gamma-RCS lymphoma cells, although in each case 100 U IL 2 were given per injection. Similar SN injections caused two- to threefold increases in responses of nondefective F1 hybrids. Pretreatment with lymphokine before TNP-Ficoll injection had no effect. Additional injection of monoclonal anti-IgD decreased the effect of lymphokine. Responses to TNP-Ficoll of CBA/J spleen cells were enhanced in vitro by SN as shown previously. Although responses by CBA/N spleen cells to TNP-polyacrylamide were increased by SN, however, responses to TNP-Ficoll could not be obtained with spleen cells from the xid mice in vitro.

LPS greatly enhances the antibody response to hapten-polysaccharide conjugates, but not to hapten-protein conjugates

In confirmation of earlier findings, we observed that an injection of bacterial lipopolysaccharide (LPS) into mice caused a considerable increase in the serum concentrations of IgM and IgG (total Ig rose three- to four-fold in 7 days), and a corresponding increase in the concentrations of "natural" anti-(3-iodo-4-hydroxy-5-nitrophenyl) acetyl (NIP) and anti-trinitrophenol (TNP) antibodies. Our main purpose was to determine what effect LPS had on antigen-dependent responses. Hapten conjugates of a polysaccharide and of proteins were used as antigens. Hapten-protein conjugates induced a strong anti-hapten antibody response (up to 1 mg/ml of anti-hapten antibodies on day 7). Hapten-polysaccharide conjugates induced only a meagre increase in anti-hapten antibodies from the pre-immunization level (maximal concentration 65 micrograms/ml on day 7). LPS, when injected with the antigen, greatly enhanced the antibody response to the hapten-polysaccharide conjugates (up to 2.6 mg/ml of anti-hapten antibodies on day 7). It had little effect on antibody responses to hapten-protein conjugates. The combination treatment had the same effect on immunoglobulin concentrations as LPS alone.

T cell responses induced by the parenteral injection of antigen-modified syngeneic cells. I. Induction, characterization, and regulation of antigen-specific T helper cells involved in delayed-type hypersensitivity responses

This report presents evidence for the role of antigen-specific helper T cells in augmenting the in vivo development of delayed-type hypersensitivity (DTH) responses to both hapten and protein antigens. The role of these helper T cells in the in vivo induction and regulation of DTH responses was investigated. Mice were primed subcutaneously with optimal numbers (3 X 10(7)) of either protein antigen- or TNP-modified syngeneic spleen cells. Primed spleen or lymph node cells, but not thymocytes or unprimed cells, were found to significantly augment the DTH response of syngeneic recipients injected subcutaneously with suboptimal numbers (1 to 2 X 10(6)) of antigen-modified syngeneic cells. Primed spleen or lymph node cells augmented both in vivo ear swelling reactions and in vitro antigen-induced T cell proliferative responses in recipient animals. The helper effect was found to be mediated by a population of radioresistant, Thy-1+, Lyt-1+2-, I-A+ cells, a phenotype identical to that of antigen-specific Tprlf cells found in primed lymph nodes. In contrast, effector TDH cells were found to be Thy-1+, Lyt-1+2-, I-A- cells. Splenic T cells from TNP-primed mice augmented TNP-specific DTH responses, but not DTH to irrelevant protein antigens, and vice versa. Helper T cell induction correlated with the presence of H-2 I-region determinants on the inducer cells, because antigen-modified spleen cells were the most efficient inducers, modified thymocytes were less efficient, and modified erythrocytes were ineffective. Mapping studies also indicated that I-region identity between the antigen-modified spleen cell immunogen and the Th donors was both necessary and sufficient for DTH Th cell induction. In addition, functional helper T cell activity could be both specifically tolerized and suppressed by the transfer or suppressor T cells raised by the i.v. injection of antigen-modified syngeneic cells.

The induction of tolerance to allergenic chemicals

The first recognition of tolerance and partial tolerance to attempted sensitization with simple allergenic chemicals is described. A proper designation would be the Frei-Sulzbeger-Chase phenomenon. Coupling with self occurs in these experiments; there is not only resistance to developing contactant-type sensitivity but also to synthesis of immunoglobulins toward hapten-self complexes. The onset of tolerance is initiated by small doses of haptens. Various facets of these investigations speak strongly against a concept of clonal deletion as an explanation. The concept of the relative numbers of suppressor and effector cells also argues against clonal deletion. Evidence exists that tolerance can be transferred to syngeneic animals by cells during parabiosis (Polak, this volume). Contact sensitivity can be imposed on a tolerized guinea pig through a transfer of cells from outbred sensitized donors, but the tolerance remains after the transferred cells have been rejected. Tolerance could not be overcome in inbred guinea pigs by infusing normal or functionally "labeled" cell populations from close relatives before attempting sensitization, a fact that supports the existence of overwhelmingly large numbers of suppressor cells. Various routes of application have been explored to find a way to establish the tolerant state. The most successful are (1) feeding of small doses and (2) two intravenous injections of massive doses of DNP- or TNP-benzene sulfonates. Several other methods will effect tolerance in about half the animals, but experimental sensitization is the only method that will locate the tolerized animals.

LPS regulation of the immune response: suppression of immune responses to orally administered T-independent antigen

The regulation of immune responses to gastrically administered TI antigens has been investigated, and the characterization of a regulatory cell population has been performed. Intragastric administration of TNP-haptenated homologous erythrocytes (TNP-MRBC) induced splenic IgM anti-TNP PFC responses in LPS nonresponsive C3H/HeJ mice that were higher than those in LPS-responsive C3H/HeN mice and similar to those noted in athymic (nu/nu) C3H/HeN animals. The simultaneous intragastric administration of LPS with TNP-MRBC augmented immune responses in a manner similar to that previously reported for parenterally administered LPS and antigen. Further, LPS-induced augmentation of TNP-MRBC responses was greater in athymic mice. These findings were substantiated using in vitro spleen cultures. Intragastric challenge with a 2nd TI antigen, TNP-LPS, induced approximately 8-fold higher splenic anti-TNP PFC responses in athymic C3H/HeN mice compared with those in euthymic littermates. By admixture of B and T cell populations, it was demonstrated that the host responsiveness to TNP-LPS was negatively regulated by suppressor cells. Suppressive activity resided in a Thy 1.2-bearing, irradiation-resistant, nylon wool-nonadherent cell population. These cells could be demonstrated in spleen and Peyer's patches from young or old LPS-responsive C3H/HeN mice, but not in tissues from LPS nonresponsive C3H/HeJ mice. The specificity of the regulator cells was not limited to TNP-LPS responses, since immune responsiveness to another TI antigen, TNP-dextran, was also under the control of this cell population. These studies confirm the TI nature of TNP-MRBC and indicate that immune responses to gastrically administered antigens such as TNP-LPS, TNP-dextran, and possibly TNP-MRBC are negatively regulated by a suppressor T cell population. A role for endogenous LPS in the generation of regulator cells and the effect of these cells on host responses to gut-derived antigens is discussed.

Studies on in vivo priming of the TNP-reactive cytotoxic effector cell system. I. Comparison of the effects of intravenous inoculation with TNP-conjugated cells on the development of contact sensitivity and cell-mediated lympholysis

A comparison was made of the effects of i.v. inoculation of trinitrophenyl-(TNP) conjugated syngeneic cells on the subsequent in vitro generation of TNP-reactive effector cell activity and on the in vivo development of TNP-contact sensitivity. The administration of syngeneic TNP-conjugated spleen cells before 2,4,6-trinitro-1-chlorobenzene (TNCB) painting abolished the capability of animals to develop TNP-contact sensitivity. In contrast, the same treatment resulted in an appreciable augmentation in the generation of TNP-reactive cytotoxic effector cell activity as measured by subsequent in vitro sensitization with TNP-conjugated cells. The possible mechanisms by which enhanced TNP-reactive cytotoxic effector cell activity was elicited under conditions identical to those that induced unresponsiveness for TNP-contact sensitivity are discussed.

Split unresponsiveness to the trinitrophenyl determinant. I. Manoeuvers which suppress either humoral or cell-mediated immune responses

2,4,6-Trinitrobenzene sulfonic acid (TNBS) injected intravenously (i.v.) makes mice fully tolerant to the trinitrophenyl (TNP) determinant. Administration of in vitro TNP-labeled syngeneic erythrocytes or thymocytes renders mice unable to develop contact sensitivity to picryl chloride, while the humoral anti-TNP responses seem to be unaffected. The reverse was found after pretreatment of mice with TNP-labeled isologous IgG (MGG) since only anti-TNP antibody responses, but not contact sensitivity to picryl chloride, were significantly reduced. TNP-coupled macrophages given to animals suppressed both the cell-mediated and humoral responses, and this might be due to the presence on their surface of TNP-labeled cytophilic antibody. TNBS administered i.v. binds to circulating proteins and formed blood elements. Thus the split unresponsiveness affecting either humoral or cell-mediated compartments after the injection of TNP-MGG or of haptenated cells respectively, is presumably due to dissecting events which in vivo after the injection of TNBS, occur simultaneously. These results may be interpreted to indicate that split unresponsive states to TNP determinants are mediated two independent mechanisms which require different tolerogen presentations to be triggered.