The regulation of resistance to Schistosoma mansoni by auto-anti-idiotypic immunity

These studies explore auto-anti-idiotypic mechanisms as potential regulators of the protective immune response against Schistosoma mansoni. Anti-idiotypic responses were stimulated by immunization of mice with lymphoblasts, bearing specific idiotypic receptors. These receptors were produced in vitro by stimulation of Ag-reactive T cells by soluble cercarial immunogen, keyhole limpet hemocyanin, or Con A. The animals were then exposed to irradiated cercariae, keyhole limpet hemocyanin, or SRBC. The results indicate that the soluble cercarial immunogen lymphoblast recipient mice demonstrated reduction in a number of parameters of their immune response to schistosome Ag, including resistance to challenge by parasites. These changes were immunologically specific. Anti-idiotypic antibodies and anti-clonotypic T cell reactivity was demonstrated in the lymphoblast immunized mice. The suppression of reactivity in LBM was mediated by Lyt-1-, L3T-4-, and Lyt-2+ lymphocytes. These studies suggest that idiotypically dependent pathways might be important for the regulation of resistance to schistosomiasis.     

Comparison of Th1- and Th2-associated immune reactivities stimulated by single versus multiple vaccination of mice with irradiated Schistosoma mansoni cercariae.

Mice immunized against Schistosoma mansoni by a single percutaneous exposure to radiation-attenuated parasite larvae demonstrate partial resistance to challenge infection that has been shown to correlate with development of cell-mediated immunity, whereas mice hyperimmunized by multiple exposure to attenuated larvae produce antibodies capable of transferring partial protection to naive recipients. Measurement of Ag-specific lymphokine responses in these animals suggested that the difference in resistance mechanisms may be due to the differential induction of Th subset response by the two immunization protocols. Thus, upon Ag stimulation, singly immunized mice predominantly demonstrated responses associated with Th1 reactivity, including IL-2 and IFN-gamma production, whereas multiply immunized animals showed increased IL-5, IL-4, and IgG1 antibody production associated with enhanced Th2 response. These responses demonstrated some degree of organ compartmentalization, with splenocytes demonstrating higher Th1-related lymphokine production and cells from draining lymph nodes showing stronger proliferation and Th2 type reactivity. However, hyperimmunized mice also continued to demonstrate substantial Th1-associated immune reactivity. Moreover, in vivo Ag challenge elicited activated larvacidal macrophages in hyperimmunized animals. These observations indicate that protective cell-mediated mechanisms associated with induction of CD4+ Th1 cell reactivity predominate in singly vaccinated mice. Further vaccination stimulates Th2 responses, such as enhanced IgG1 production, that may also contribute to protective immunity.     

Paramyosin-enhanced clearance of Brugia malayi microfilaremia in mice

Progress in development of a vaccine against human filariasis has been hampered by lack of knowledge of the biochemical structure of specific Ag that induce protective immunity in experimental hosts. In the current study, antiserum to infective third-stage larvae of Brugia malayi was used to select potentially protective Ag shared by microfilariae (mf) and adult worms. A major Ag of 97 kDa (Bm 97) was identified by immunoblotting and isolated by electroelution. Immunization of mice with 2 micrograms electroeluted Bm 97 induced partial resistance to subsequent i.v. challenge with live B. malayi mf (40 to 60% reduction in parasitemia compared to controls, p less than 0.05). Immunoblot studies of B. malayi mf and adult worm lysates showed reactivity of a 97-kDa molecule with monospecific antiserum to Schistosoma mansoni paramyosin. In addition, mouse antibody to Bm 97 reacted with a 97-kDa molecule contained in wild-type Caenorhabditis elegans but not in two mutant strains deficient for paramyosin. Subcutaneous injection of mice with paramyosin (5 micrograms twice at a 2-wk interval) purified from C. elegans or B. malayi by salt precipitation induced resistance to microfilaremia (21 to 60% lower intensities than controls, p less than 0.01). These data indicate that the invertebrate muscle protein paramyosin enhances clearance of blood-borne stages of lymphatic filariae. Examination of the ability of paramyosin to induce resistance in third-stage larvae-challenged hosts is warranted.     

The mouse antibody response to Trichinella spiralis defines a single, immunodominant epitope shared by multiple antigens.

Immunoblot analysis was used to characterize the Trichinella spiralis L1 larval Ag recognized by antisera from T. spiralis-infected AKR/J mice. Antisera were analyzed for reactivity with crude worm extract, excretory/secretory proteins and cuticle proteins from L1 larvae. The response was biphasic; antibodies against one set of Ag were detected 13 days after infection (group I Ag), and antibodies against a different set of Ag were detected 35 days after infection (group II Ag). Excretory/secretory and cuticle proteins were recognized only by antibodies produced late in infection. The predominant isotype in day 42 antiserum was IgG1, and 80% of these IgG1 antibodies reacted with a stage-specific determinant shared by virtually all group II Ag. A mAb reactive with the shared determinant was used to purify the group II Ag from L1 larval extract. Such affinity-purified Ag were protective when used to immunize mice against subsequent infection, and T cells from infected mice proliferated when cultured with these Ag in vitro. Other mouse strains also made a strong serum antibody response to the group II Ag. We hypothesize that immune responses to the shared epitope play an important role in determining the outcome of the host-parasite interaction during infection.     

Trypanocidal drugs and the role of kidney forms of Trypanosoma (Herpetosoma) musculi in immunity of mice against reinfection

Adrenals, hearts, kidneys, livers, lungs, and spleens were removed from C3H/Anf mice which had been inoculated with Trypanosoma (Herpetosoma) musculi and no longer exhibited parasitemias. Imprints of each organ were examined microscopically, and each was homogenized and injected into recipient mice. It was confirmed that trypanosomes could be detected only in the donor kidneys. Lampit or Ethidium treatment eliminated bloodstream and kidney forms when administration was initiated after the development of patent parasitemias. However, mice treated with Lampit on the same day they were inoculated with T. musculi developed parasitemias later than animals injected with drug after parasites had appeared in their blood. Both Lampit and Ethidium depressed antibody production as detected in enzyme-linked immunosorbent assays of antisera from animals having parasitemias at the time of treatment. The elimination of kidney forms by Lampit or Ethidium treatment did not reduce the resistance of mice to reinfection by T. musculi 12 weeks or 15 and 22 weeks, respectively, after the initial inoculation of these animals with the parasites. Kidney forms were not required for the sustained protective immunity of the mice against reinfection during the intervals of these experiments.     

The influence of adjuvant on induction of protective immunity by a non-living vaccine against schistosomiasis

Mice were protected against subsequent infection with Schistosoma mansoni by intradermal or s.c. vaccination with killed schistosomula or soluble parasite extracts and bacillus Calmette-Guérin (BCG). Treatment with i.p. immunization was somewhat less effective, whereas i.m. vaccination failed to elicit protective immunity. The level of resistance induced by intradermal immunization was influenced by the strain of BCG used, and isolated BCG cell walls did not reliably substitute for whole BCG organisms as adjuvant. Bordetella pertussis vaccine and saponin were also able to function as adjuvants for protective immunity in this model, whereas other immunopotentiators including Corynebacterium parvum and aluminum hydroxide were ineffective. No correlation between resistance to challenge infection and antibody levels was detected. Animals immunized intradermally using either protective or non-protective adjuvants all showed minimal humoral reactivity against schistosomulum surface Ag but strong IgG response to soluble parasite components including paramyosin, which is the major serologically recognized Ag in mice vaccinated intradermally with schistosome Ag plus BCG and is protective in this model. In contrast, a strong correlation was observed between resistance and Ag-specific cell-mediated reactivity, including IFN production by T lymphocytes in vitro and macrophage activation in vivo. These results further substantiate the hypothesis that protection in this model is based on cell-mediated immune effector mechanisms. Moreover, they may be of general relevance in the design of vaccination protocols using other Ag or against other infectious agents.     

Isolation of protective T cells from BALB/cJ mice chronically infected with Leishmania donovani

BALB/cJ mice, which are homozygous for Lshs on chromosone 1, are genetically susceptible to Leishmania donovani (S3), but spontaneously reduce their parasite burdens late in the course of infection. Spleens from chronically infected mice (5 to 8 mo) were found to have T cells that responded to leishmanial Ag by proliferating and secreting immune IFN. An IFN-secreting T cell line derived from the spleen of a chronically infected mouse, after boosting with leishmanial Ag and treatment with Pentostam to kill residual parasites, was able to activate macrophages to kill amastigotes in vitro. Furthermore, after adoptive transfer of this cell line, naive BALB/cJ mice challenged with amastigotes demonstrated a 42-fold reduction in parasite burden compared to controls. Four of five clones derived from the protective T cell line secreted IFN and proliferated between days 7 and 14 after Ag stimulation. All clones were Ly1+2-, L3T4+. Another T cell line, which had Ly1+2-, L3T4+ phenotype, was derived from the lymph nodes of s.c. immunized, uninfected mice. It multipled but never produced IFN in response to leishmanial Ag and failed to protect macrophages against L. donovani infection in vitro or in vivo. This nonprotective T cell line and the fifth clone from the protective line, which also did not secrete IFN, proliferated between days 2 and 7 after Ag stimulation. In summary, leishmania-responsive helper/inducer T cells, which produced IFN but were slow to proliferate in response to Ag in vitro and which were able to activate macrophages to reduce amastigotes in vitro and in vivo, are present in chronically infected BALB/cJ mice and may mediate the decrease in parasite burden during chronic infection.     

Adoptive protection against Plasmodium chabaudi adami malaria in athymic nude mice by a cloned T cell line

T cell-dependent, cell-mediated immune mechanisms have been shown to contribute to resistance against malaria. Because the identity of plasmodial Ag responsible for the activation of these protective immune responses remains unknown, a major step in isolating these potential immunizing agents will be the development of adequate screening procedures designed to identify important T cell Ag. This study focused on the isolation of protective T cell clones that may play a pivotal role in this process. A T cell clone designated CTR2.1 and two subclones derived from it adoptively transferred protection to athymic nude mice infected with Plasmodium chabaudi adami, a murine malarial parasite known to be recognized by protective thymus-dependent immune mechanisms. The protective T cell clone displayed a L3T4+, Lyt-2- surface phenotype and secreted both IFN-gamma and IL-2 after stimulation with solubilized parasites in vitro. This is the first report of results demonstrating a cloned T cell line capable of providing adoptive protection against malaria in vivo. More importantly, CTR2.1 and other protective T cell clones may provide for the identification of plasmodial antigenic epitopes recognized by important cell-mediated immune mechanisms during acute malarial infection.     

Protective efficacy of a cloned Brugia malayi antigen in a mouse model of microfilaremia

Immunization of mice with irradiated Brugia larvae or parasite extracts has been shown to induce partial resistance to microfilaremia and enhance clearance of infective larvae. We recently reported the cloning of a 548 amino acid 62-kDa Brugia malayi Ag identified on the basis of reactivity with antisera to a subset of protective microfilarial Ag. Our study describes the protective efficacy against microfilaremia in mice, immunogenicity, and parasite stage-specificity of this candidate vaccine molecule. Immunization of Swiss or BALB/c mice with 1 to 3 micrograms of a 92-kDa trpE fusion protein encoding amino acids 1-479 reduced the intensity of microfilaremia by 40 to 60% compared to control animals given buffer or bacterial trpE (p less than 0.01 to 0.001). Mice immunized with the 92-kDa fusion protein developed delayed-type hypersensitivity reactivity to B. malayi as assessed by enhanced footpad swelling 24 and 48 h after intradermal injection of adult worm extract and in vitro lymph node mononuclear cell proliferation (3H-thymidine uptake) in response to the fusion protein (mean +/- SD stimulation index 4.7 +/- 0.8 vs 2.0 +/- 1.4 for trpE, p less than 0.05). Proliferative responses of lymph node cells coincubated with three other fusion proteins corresponding to the filarial protein truncated from its carboxyl-terminus suggest that dominant T cell epitopes of the 62-kDa Ag are encompassed by amino acids 437-479. Rabbit antibody to the 92-kDa trpE fusion protein immunoprecipitated a 62-kDa polypeptide from [35S] methionine biosynthetically labeled B. malayi microfilariae, adult female, and adult male worms. These data indicate that a recombinant Ag expressed in several developmental stages of B. malayi is capable of inducing partial resistance against microfilariae and Ag-specific T cell responses in mice.     

Induction of protective immunity against Schistosoma mansoni by a nonliving vaccine. II. Response of mouse strains with selective immune defects

The efficacy of a new vaccination procedure against Schistosoma mansoni, involving intradermal injection of nonliving antigen combined with the bacterial adjuvant Mycobacterium bovis strain bacillus Calmette Guérin, was tested in several strains of mice. Development of protection against subsequent infection was compared with in vivo skin test reactivity and in vitro humoral reactivity to soluble and surface-associated schistosome antigens. Significant levels of resistance and immune response were displayed by many inbred mouse strains, including C57BL/6J, C3H/HeN, and CBA/J, as well as outbred Swiss-Webster mice. However, no definite correlation was observed between the level of any particular immune response and the level of resistance to challenge S. mansoni infection. Development of protective immunity was also examined in mice with various immune defects, to determine whether these responses are relevant to resistance in this model. Animals with defective specific immediate hypersensitivity response due to deficiencies in IgE (SJL/J) or mast cell (W/Wv) production displayed strong resistance as a result of immunization. Likewise, mice bearing the lpsd (C3H/HeJ) or xid (CBA/N) mutations, affecting cellular or humoral response to certain thymus-independent antigens, developed significant levels of resistance after immunization. A/J mice, with defects in cellular recognition of bacterial endotoxin as well as deficiencies in natural killer cell activity and complement function, also showed significant protective immunity. Thus, these reactivities do not appear to be essential to the resistance against S. mansoni induced by the nonliving vaccine. Two nonresponder strains were identified, P and BALB/c. P mice were defective in specific delayed hypersensitivity response as well as resistance to infection. However, BALB/c mice showed no obvious immune deficiencies at the time of challenge. These results agreed with previous findings in mice immunized by exposure to radiation-attenuated cercariae with one exception; BALB/c mice were protected by vaccination with irradiated cercariae but not by the nonliving vaccine. Thus, further examination of immune response in mice identified in this study as high and low responder strains should allow characterization of critical immune resistance mechanisms induced by the nonliving vaccine, as well as immune mechanisms operating in common between these two models of resistance to S. mansoni.     

Induction of protective immunity against Schistosoma mansoni by a non living vaccine. I. Partial characterization of antigens recognized by antibodies from mice immunized with soluble schistosome extracts

A single intradermal injection of frozen and thawed schistosomula in conjunction with the bacterial adjuvant Mycobacterium bovis strain Bacille Calmette Guerin, Phipps substrain (BCG) induced significant levels of resistance to challenge Schistosoma mansoni infection in C57BL/6 mice. Immunization with the aqueous fraction remaining after 100,000 X G centrifugation of the larval lysate was also protective under these conditions, suggesting that some immunogenic determinants may not be membrane associated. Frozen-thawed cercariae and soluble components of adult worms also protected against challenge infection in these experiments. These observations indicate that soluble immunogens are present in both early and late developmental stages of the parasite, and therefore may be good candidate antigens for an immunochemically defined vaccine against schistosomiasis. Induction of humoral reactivity against soluble or membrane antigens was examined in mice protected against cercarial challenge by prior exposure to frozen-thawed larvae, soluble larval, or soluble adult antigens plus BCG. Animals that were immunized with frozen-thawed larvae produced low but significant levels of antibodies against larval surface antigens when examined by indirect immunofluorescence or by immunoprecipitation of surface-labeled schistosomula. Mice immunized with soluble antigens, however, showed negligible antibody reactivity against surface membrane antigens. Because mice immunized with soluble antigens were resistant to challenge infection, these results strongly suggest that anti-surface membrane reactivity is not required in the mechanism of protective immunity in this model. Sera from mice immunized with either total freeze-thaw larval lysate or soluble schistosome extracts all showed strong reactivity against soluble antigens, as detected by ELISA. Western blot analysis showed these antisera to react with a restricted number of high m.w. antigens that were present both in schistosomula and in adult worms. These antigens are therefore likely to play a major role in the development of resistance in this model as immunogens and/or as targets of protective immune response.     

Dendritic cells in the induction of protective and nonprotective anticryptococcal cell-mediated immune responses

Dendritic cells (DC) can be divided into three subsets, Langerhans cells, myeloid DC (MDC), and lymphoid DC (LDC), based upon phenotypic and functional differences. We hypothesized that different DC subsets are associated with the development of protective vs nonprotective cell-mediated immune (CMI) responses against the fungal pathogen, Cryptococcus neoformans. To test this, mice were immunized with protective and/or nonprotective immunogens, and DC subsets in draining lymph nodes were assessed by flow cytometry. The protective immunogen (cryptococcal culture filtrate Ag-CFA), in contrast to the nonprotective immunogen (heat-killed cryptococci-CFA), the nonprotective immunogen mixed with the protective immunogen (cryptococcal culture filtrate Ag + heat-killed cryptococci-CFA), or controls, stimulated significant increases in total leukocytes, Langerhans cells, MDC, LDC, and activated CD4+ T cells in draining lymph nodes. The protective immune response resulted in significantly increased levels of anticryptococcal delayed-type hypersensitivity reactivity and activated CD4+ T cells at the delayed-type hypersensitivity reaction site. Draining lymph node LDC:MDC ratios induced by the protective immunogen were significantly lower than the ratios induced by either immunization in which the nonprotective immunogen was present. In contrast, mice given the nonprotective immunogen had LDC:MDC ratios similar to those of naive mice. Our data indicate that lymph node Langerhans cells and MDC are APC needed for induction of the protective response. The predominance of LDC in mice undergoing nonprotective responses suggests that lymph node LDC, like splenic LDC, are negative regulators of CMI responses. In addition to showing DC subsets associated with functional differences, our data suggest that the LDC:MDC balance, which can be modulated by the Ag, determines whether protective or nonprotective anticryptococcal CMI responses develop.     

Schistosoma mansoni: The attrition of a challenge infection in mice immunized with highly irradiated live cercariae

Mice immunized percutaneously with 400 Schistosoma mansoni cercariae given 20 kR of ⁶⁰Co irradiation were shown to develop an immunity in which nearly 80% of the parasites that would be expected to survive in control mice were killed. The major attrition of parasites was shown to occur within the first 4 days after challenge. Marked differences in the number of parasites which were recovered from the skin of immune mice and the failure of the majority of parasites to reach the lungs of immune mice indicated that the major site of attrition was in the skin. A further trickle of parasite deaths was evident beyond Day 5, but after Day 14 no further attrition of parasites appeared to occur. Mice immunized in the abdominal skin demonstrated similar levels of immunity whether challenged in the abdominal skin or in the ear. Immunization intramuscularly with irradiated schistosomula induced a much lower level of resistance and the marked parasite attrition in the skin at Day 2 was absent. Immunization with only 50 irradiated cercariae was shown to induce a level of skin immunity equivalent to that seen with 400 irradiated cercariae. The majority of cercariae given 20 kR of ⁶⁰Co irradiation remained in the skin; approximately 2% only reached the lungs. These studies demonstrate that percutaneous immunization of mice with highly irradiated cercariae induced a strong immunity which was largely effective in the skin. This immunity differed from that developed by chronically infected mice where the major attrition of parasites occurs after the lung phase of migration. The results also suggest that the penetration or persistence in the skin of live attenuated schistosomula may play a crucial role in the induction of a high level of skin immunity.     

Dermal dendritic cells, and not Langerhans cells, play an essential role in inducing an immune response

Langerhans cells (LCs) serve as epidermal sentinels of the adaptive immune system. Conventional wisdom suggests that LCs encounter Ag in the skin and then migrate to the draining lymph nodes, where the Ag is presented to T cells, thus initiating an immune response. Platelet-activating factor (PAF) is a phospholipid mediator with potent biological effects. During inflammation, PAF mediates recruitment of leukocytes to inflammatory sites. We herein tested a hypothesis that PAF induces LC migration. Applying 2,4-dinitro-1-fluorobenzene (DNFB) to wild-type mice activated LC migration. In contrast, applying DNFB to PAF receptor-deficient mice or mice injected with PAF receptor antagonists failed to induce LC migration. Moreover, after FITC application the appearance of hapten-laden LCs (FITC+, CD11c+, Langerin+) in the lymph nodes of PAF receptor-deficient mice was significantly depressed compared with that found in wild-type mice. LC chimerism indicates that the PAF receptor on keratinocytes but not LCs is responsible for LC migration. Contrary to the diminution of LC migration in PAF receptor-deficient mice, we did not observe any difference in the migration of hapten-laden dermal dendritic cells (FITC+, CD11c+, Langerin-) into the lymph nodes of PAF receptor-deficient mice. Additionally, the contact hypersensitivity response generated in wild-type or PAF receptor-deficient mice was identical. Finally, dermal dendritic cells, but not LCs isolated from the draining lymph nodes after hapten application, activated T cell proliferation. These findings suggest that LC migration may not be responsible for the generation of contact hypersensitivity and that dermal dendritic cells may play a more important role.     

Purification and partial characterization of immobilization antigens from Ichthyophthirius multifiliis.

Ichthyophthirius multifiliis, a parasitic ciliate of freshwater fishes, was found to have surface antigens (Ag) which elicited immobilizing antibodies (Ab) when injected into rabbits. An effort was made to purify and characterize these Ag (referred to as immobilization Ag) because of their potential role in protective immunity in fishes. Mice immunized with theront cilia were used for production of immobilizing monoclonal antibodies (MAb). Hybridomas were screened by indirect immunofluorescent light microscopy and immobilization of live parasites. Six hybridomas producing immobilizing MAb were cloned. Immobilizing MAb were used to affinity purify Ag solubilized with Triton X-114 and Na deoxycholate. Two membrane protein Ag of approximately 48 and 60 kDa were identified. Immobilizing MAb failed to react with these Ag on Western blots and, conversely, MAb that reacted with the Ag on Western blots did not immobilize live organisms. These results suggest that immobilization required native conformational epitopes which were altered by Western blotting procedures. Individual MAb reactive on Western blots recognized both the 48- and 60-kDa proteins indicating the presence of common epitopes. Affinity purified Ag elicited immobilizing antisera when injected into rabbits, mice, and channel catfish.     

The regulation of resistance to Schistosoma mansoni by auto-anti-idiotypic immunity. III. An analysis of effects on epitopic recognition, idiotypic expression, and anti-idiotypic reactivity at the clonal level.

Auto-anti-idiotypic mechanisms can regulate the protective immune response against Schistosoma mansoni. Anti-idiotypic responses were stimulated by immunization of mice either with nonspecifically induced lymphoblasts, produced with Con A, or with Ag-induced lymphoblasts bearing specific idiotypic receptors. The effect of the induced anti-idiotypic response upon clonotypic cellular reactivity was assessed in vitro through the suppression of antigen-mediated blast transformation by cloned T cells and in vivo by suppression of resistance to S. mansoni and delayed-type hypersensitivity responses against specific Ag. Differential regulation of humoral immune responses was studied at the levels of specific epitopic recognition, the expression of specific Id, and the production of anti-idiotypic responses directed against mAb bearing specific Id. Anti-idiotypic sensitization resulted in variable (10 to 90%) suppression of the immune response to discrete antigenic epitopes, the expression of specific idiotypic phenotypes, and anti-idiotypic, antiparatopic responses against T cell clonotypes and antibody idiotypic phenotypes. In vitro admixture and in vivo challenge studies resulted in consonant differential suppression. Thus idiotypic regulation can mold the fine specificities of the protective immune response to S. mansoni at the clonal level and may provide an approach to optimize the expression and assessment of resistance.     

Purification and Partial Characterization of Immobilization Antigens from Ichthyophthirius multifiliis

ABSTRACT Ichthyophthirius multifiliis , a parasitic ciliate of freshwater fishes, was found to have surface antigens (Ag) which elieited immobilizing antibodies (Ab) when injected into rabbits. An effort was made to purify and characterize these Ag (referred to as immobilization Ag) because of their potential role in protective immunity in fishes. Mice immunized with theront cilia were used for production of immobilizing monoclonal antibodies (MAb). Hybridomas were screened by indirect immunofluorescent light microscopy and immobilization of live parasites. Six hybridomas producing immobilizing MAb were cloned. Immobilizing MAb were used to affinity purify Ag solubilized with Triton X-114 and Na deoxycholate. Two membrane protein Ag of approximately 48 and 60 kDa were identified. Immobilizing MAb failed to react with these Ag on Western blots and, conversely, MAb that reacted with the Ag on Western blots did not immobilize live organisms. These results suggest that immobilization required native conformational epitopes which were altered by Western blotting procedures. Individual MAb reactive on Western blots recognized both the 48- and 60-kDa proteins indicating the presence of common epitopes. Affinity purified Ag elicited immobilizing antisera when injected into rabbits, mice, and channel catfish.     

Evidence for the functional binding in vivo of tumor rejection antigens to antigen-presenting cells in tumor-bearing hosts

Spleen cells of BALB/c mice bearing a syngeneic CSA1M fibrosarcoma were treated with anti-Thy-1.2 antibody plus C, yielding a T cell-depleted, APC-containing fraction. The APC-containing fraction was first tested for its capacity to present exogenous modified-self or another tumor (Meth A) Ag after in vitro pulsing. The results showed comparable Ag-presenting capacities to those obtained by APC-containing fraction from normal spleen cells, indicating that APC function is not affected in tumor-bearing mice. We next examined whether APC from CSA1M-bearing mice bind endogenously generated CSA1M tumor Ag onto its surfaces to stimulate tumor-specific T cells. Five rounds of inoculation of APC-containing fraction from CSA1M-bearing mice without further in vitro pulsing resulted in the induction of potent anti-CSA1M immune resistance. The involvement of anti-CSA1M T cells in the induction of anti-CSA1M immunity was excluded by the fact that the in vivo immunity was excluded by the fact that the in vivo immunity was delivered by Thy-1+ cell-depleted, but not by Thy-1+ cell-enriched fractions of spleen cells from CSA1M-bearing mice. Moreover, the failure of Sephadex G10-passed spleen cells to deliver anti-CSA1M resistance demonstrated the absolute requirement of APC for inducing the in vivo immunity. Finally, this in vivo resistance was found to be tumor specific, because APC fractions from CSA1M-bearing and Meth A-bearing BALB/c mice induced immune resistance selective against the corresponding tumor cell challenge. These results indicate that APC from tumor-bearing hosts can not only exert unaffected APC function against exogenous Ag, but also function to present tumor Ag generated endogenously in the tumor-bearing state and to produce tumor-specific immunity in vivo.     

Resistance in murine schistosomiasis is contingent on activated IL-2 receptor-bearing L3T4+ lymphocytes, negatively regulated by Lyt-2+ cells, and uninfluenced by the presence of IL-4

These studies assess the roles of subpopulations of T lymphocytes in inducing and modulating resistance to Schistosoma mansoni. C57BL/6 mice were depleted in vivo of L3T4+, Lyt-1+, Lyt-2+, IL-2R+ cells, or IL-4 by administration of appropriate mAb. Resistance and various correlative parameters of the immune response were studied in normal, depleted, and congenitally athymic mice. Depletion of T lymphocytes by anti-L3T4 or anti-IL-2R mAb reduced the development and expression of resistance, IgG2a and IgE antibody formation, and delayed type hypersensitivity reactivity against schistosome Ag. Depletion with anti-IL-4 antibody led to profound suppression of IgE-eosinophil-mediated antibody-dependent cell-mediated cytotoxicity and passive cutaneous anaphylaxis responses against the parasite and no effect on IgG2a antibody, Ag-mediated blast transformation, or resistance. Depletion of Lyt-2+ cells produced augmented development and expression of resistance and an increase in the immunological parameters of anti-schistosome reactivity. These studies suggest that protective immunity to S. mansoni in mice, induced by irradiated cercariae, is dependent on L3T4+, IL-2R+ lymphocytes and negatively regulated by Lyt-2+ cells. IL-4 does not appear to be essential for the development of resistance but is essential for the IgE response to the parasite.