A 24 year survey of amputees in Hong Kong

A 24-year retrospective study of amputees was conducted at the Prosthetic and Orthotic Unit of the Kowloon Rehabilitation Centre, the first and largest rehabilitation centre in Hong Kong. A review was made of 1821 patients and a rising trend of amputee population was demonstrated probably related to the population growth. The ratio of lower limb to upper limb amputees was 1.83 to 1. The mean age of the amputees was 39 years. The commonest cause of upper limb amputation was trauma (89%) and of lower limb amputation was infection (35%). Vascular diseases were not as common in Chinese as in Caucasian communities. These patterns of amputee population indicate the demand for prosthetic service and provide guide-lines for future development.

Cryptic epitope explains the failure of a monoclonal antibody to bind to certain isolates of Trypanosoma cruzi

A mouse monoclonal antibody, WIC 29.26 Ab, has previously been characterized as recognizing a carbohydrate epitope on a 72,000 m.w. glycoprotein (GP72) expressed on the surface of Trypanosoma cruzi epimastigotes and metacyclic trypomastigotes. This molecule has been implicated as a receptor in the control of parasite transformation, and when used as an immunogen in mice, partially protects against T. cruzi infection. In previous experiments in which a radioimmunoassay was used, WIC 29.26 Ab was found to react with approximately 50% of T. cruzi strains and clones derived from a variety of sources. In this study, we attempted to determine whether the WIC 29.26 Ab-nonreactive isolates lack the entire GP72 or merely lack the epitope recognized by this monoclonal antibody. WIC 226.4 Ab, a monoclonal antibody raised against periodate-treated GP72, reacted in an immunofluorescence assay with all strains and clones studied, including those which had not reacted with WIC 29.26 Ab. Likewise, two polyvalent rabbit sera, directed specifically against GP72, bound to all T. cruzi isolates tested. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of detergent lysates of surface-labeled epimastigotes immunoprecipitated with WIC 29.26 Ab showed that the epitope bound by this antibody was present in all but one of the parasites that were surface-nonreactive, as well as in all those that were surface-reactive. WIC 29.26 Ab precipitated a single 72K Mr band from most strains and clones, but in several cases 79K Mr and 66K Mr bands were seen. Isolates from both the surface-reactive and the surface-nonreactive groups showed the latter pattern. These results demonstrate that GP72, or similar electrophoretic variants--and with one exception, the carbohydrate epitope bound by WIC 29.26 Ab--are present in the surface membrane of all strains and clones tested. This observation suggests that in intact epimastigotes of the surface-nonreactive isolates, the epitope is not accessible because of structural changes in the molecule itself or because of differences in the membrane environment of GP72.

Cryptic epitope explains the failure of a monoclonal antibody to bind to certain isolates of Trypanosoma cruzi

A mouse monoclonal antibody, WIC 29.26 Ab, has previously been characterized as recognizing a carbohydrate epitope on a 72,000 m.w. glycoprotein (GP72) expressed on the surface of Trypanosoma cruzi epimastigotes and metacyclic trypomastigotes. This molecule has been implicated as a receptor in the control of parasite transformation, and when used as an immunogen in mice, partially protects against T. cruzi infection. In previous experiments in which a radioimmunoassay was used, WIC 29.26 Ab was found to react with approximately 50% of T. cruzi strains and clones derived from a variety of sources. In this study, we attempted to determine whether the WIC 29.26 Ab-nonreactive isolates lack the entire GP72 or merely lack the epitope recognized by this monoclonal antibody. WIC 226.4 Ab, a monoclonal antibody raised against periodate-treated GP72, reacted in an immunofluorescence assay with all strains and clones studied, including those which had not reacted with WIC 29.26 Ab. Likewise, two polyvalent rabbit sera, directed specifically against GP72, bound to all T. cruzi isolates tested. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of detergent lysates of surface-labeled epimastigotes immunoprecipitated with WIC 29.26 Ab showed that the epitope bound by this antibody was present in all but one of the parasites that were surface-nonreactive, as well as in all those that were surface-reactive. WIC 29.26 Ab precipitated a single 72K Mr band from most strains and clones, but in several cases 79K Mr and 66K Mr bands were seen. Isolates from both the surface-reactive and the surface-nonreactive groups showed the latter pattern. These results demonstrate that GP72, or similar electrophoretic variants--and with one exception, the carbohydrate epitope bound by WIC 29.26 Ab--are present in the surface membrane of all strains and clones tested. This observation suggests that in intact epimastigotes of the surface-nonreactive isolates, the epitope is not accessible because of structural changes in the molecule itself or because of differences in the membrane environment of GP72.

Defective vaccine-induced immunity to Schistosoma mansoni in P strain mice. I. Analysis of antibody responses

Inbred P4 strain mice have previously been shown to be uniquely defective in their resistance to challenge infection induced by irradiated cercariae of Schistosoma mansoni. To assess whether the low levels of resistance developed by vaccinated P mice could be due to a defective antibody response, we compared the anti-schistosomulum antibody responses in vaccinated P animals with those occurring in vaccinated C57BL/6J (B6) mice, a strain that consistently develops high levels of resistance to challenge infection. Our results indicate that vaccinated P mice develop levels of total anti-schistosomulum antibodies that are significantly lower than those occurring in B6 mice for at least 15 wk after immunization, with the exception of the fifth week, at which time the responses are indistinguishable. Further analysis revealed that the defect in P strain antibody response occurs specifically in the IgM isotype and that specific IgM levels in P mice are less than one-half the levels in B6 mice at every time point examined. In contrast, no differences in total IgM immunoglobulins were evident when sera from normal (nonvaccinated) P and B6 mice were compared. P mouse anti-schistosomulum IgG antibody responses reached the same levels as those observed in B6 mice by 5 wk after vaccination. However, a much faster decay in IgG antibody levels occurred after this time point in P animals. No differences were observed when the levels of anti-schistosomulum antibodies occurring in each of the major IgG isotypes (IgG1, IgG2a, IgG2b, IgG3) were compared in sera from P and B6 mice vaccinated 4 wk previously. Similarly, vaccinated P and B6 mice were found to mount indistinguishable IgG anamnestic responses after challenge infection. Finally, no differences between vaccinated P and B6 mice were observed when immediate (30 min) skin test and mast cell degranulation responses to a soluble schistosome antigenic preparation were compared. The above findings suggest that P strain mice have a specific defect in their ability to mount IgM antibody responses after immunization with irradiated cercariae. The possible contribution of this defect in IgM response to the decreased resistance of vaccinated P mice to challenge infection is discussed.

Defective vaccine-induced immunity to Schistosoma mansoni in P strain mice. I. Analysis of antibody responses

Inbred P4 strain mice have previously been shown to be uniquely defective in their resistance to challenge infection induced by irradiated cercariae of Schistosoma mansoni. To assess whether the low levels of resistance developed by vaccinated P mice could be due to a defective antibody response, we compared the anti-schistosomulum antibody responses in vaccinated P animals with those occurring in vaccinated C57BL/6J (B6) mice, a strain that consistently develops high levels of resistance to challenge infection. Our results indicate that vaccinated P mice develop levels of total anti-schistosomulum antibodies that are significantly lower than those occurring in B6 mice for at least 15 wk after immunization, with the exception of the fifth week, at which time the responses are indistinguishable. Further analysis revealed that the defect in P strain antibody response occurs specifically in the IgM isotype and that specific IgM levels in P mice are less than one-half the levels in B6 mice at every time point examined. In contrast, no differences in total IgM immunoglobulins were evident when sera from normal (nonvaccinated) P and B6 mice were compared. P mouse anti-schistosomulum IgG antibody responses reached the same levels as those observed in B6 mice by 5 wk after vaccination. However, a much faster decay in IgG antibody levels occurred after this time point in P animals. No differences were observed when the levels of anti-schistosomulum antibodies occurring in each of the major IgG isotypes (IgG1, IgG2a, IgG2b, IgG3) were compared in sera from P and B6 mice vaccinated 4 wk previously. Similarly, vaccinated P and B6 mice were found to mount indistinguishable IgG anamnestic responses after challenge infection. Finally, no differences between vaccinated P and B6 mice were observed when immediate (30 min) skin test and mast cell degranulation responses to a soluble schistosome antigenic preparation were compared. The above findings suggest that P strain mice have a specific defect in their ability to mount IgM antibody responses after immunization with irradiated cercariae. The possible contribution of this defect in IgM response to the decreased resistance of vaccinated P mice to challenge infection is discussed.

Mechanisms of protective immunity against S. mansoni infection in mice vaccinated with irradiated cercariae. VI. Influence of the major histocompatibility complex

Inbred mouse strains develop different levels of resistance to challenge infection with Schistosoma mansoni in response to vaccination with irradiated cercariae. The role of the major histocompatibility complex (MHC) in determining this genetic polymorphism in acquired resistance was investigated. Previous studies suggested that inbred mice bearing either the b or d MHC haplotypes develop a higher level of vaccine induced resistance than do mice with other MHC haplotypes. An analysis of an F1 cross between an H-2b strain (C57BL/6) and an H-2k strain (C3H/HeJ) indicated that the ability to develop high levels of immunity is inherited in a dominant fashion. In order to confirm that the development of high resistance is an MHC associated trait, B10, C3H, BALB and B6 congenic mice bearing different H-2 haplotypes were compared. On either the B10, B6, or BALB background, substitution of b or d with k or a MHC alleles resulted in a decreased level of vaccine induced immunity. The observed decreases were more pronounced in BALB and B6 than in B10 congenics suggesting an influence of background (non-MHC linked) genes on protective immunity. Similarly, C3H.SW (H-2b) mice developed a significantly higher level of acquired resistance than C3H/HeSn (H-2k) mice. Cross and backcross experiments between H-2b and H-2k B6 congenic mice confirmed the dominant inheritance of high resistance as well as the MHC linkage of the trait. These data indicate that the MHC locus exerts a quantitative influence on vaccine induced resistance in certain inbred mouse strains and provide further support for the concept that the protection elicited by irradiated cercariae is the manifestation of a specific host immune response.

Strains and clones of Trypanosoma cruzi differ in their expression of a surface antigen identified by a monoclonal antibody

Four Trypanosoma cruzi strains and 50 clones derived from a total of 10 strains were assayed with a monoclonal antibody, WIC 29.26 Ab, for expression of an epitope previously demonstrated to be on the carbohydrate portion of a 72 000 Da surface glycoprotein of Y strain epimastigotes. WIC 29.26 Ab bound to only 2 of the 4 strains and 23 of the 50 clones tested. A group of 10 cloned isolates from one strain contained both reactive and non-reactive clones. Competitive inhibition studies with soluble extracts of the reactive and non-reactive isolates suggested that in addition to being absent from the surface membrane, the antigenic determinant is not synthesized by the non-reactive parasites. These data indicate that the epitope recognized by WIC 29.26 Ab is not present on all T. cruzi epimastigotes, and provide the first demonstration of clone-specific differences in a parasite antigen detected by a monoclonal antibody. No correlation was found between the reactivity of isolates with WIC 29.26 Ab and the previously investigated parameters of growth rate and modal volume.

Dichotomy in the tissue origin of schistosome acquired class I and class II major histocompatibility complex antigens

Schistosoma mansoni schistosomula recovered from the lungs of mice have previously been shown to express host-derived class I and class II major histocompatibility complex (MHC) antigens. To investigate the tissue origin of parasite-acquired MHC products, lung-stage schistosomula were obtained from a series of parent leads to F1 and F1 leads to parent bone marrow chimeras and the parasites typed by immunofluorescence for the presence of haplotype-specific K region and I region MHC determinants. The results of these experiments indicated that, despite their intravascular residence in the host, schistosomula derive all of their class I antigen from a nonhemapoietic tissue source. In contrast, the class II antigens expressed on the surface of schistosomula were found to originate from bone marrow-derived donor cells. These results support the hypothesis that MHC product acquisition by schistosomes involves selective and specific interactions with host tissue and, in the case of class I antigens, suggest that the endothelium may be a major site of host molecule uptake for the parasite.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. V. Anamnestic cellular and humoral responses following challenge infection

Mice vaccinated with radiation-attenuated cercariae display low levels of cellular and humoral immune responses toward schistosomulum antigens, as measured in vitro by lymphocyte blastogenesis and quantitation of anti-larval antibodies by indirect immunofluorescence. Both responses wane with time after vaccination. However subsequent challenge infection provokes immune responses of classical anamnestic character, being both more rapid in appearance and of greater magnitude. Antigen responsive cells appear in lymph nodes draining the challenge site within 24 hours after infection. Both circulating anti-schistosomulum surface antibodies as well as cytophilic IgE anti-worm antigen antibodies increase substantially by 1 week after challenge. All of the anamnestic circulating antibodies belong to the IgG class. Those findings support the concept that vaccine-induced resistance to Schistosoma mansoni infection involves sensitized T and B lymphocytes, and point to the possible role of post-challenge anamnestic responses in the effector mechanism of parasite killing in this model.

Differentiation of schistosomes by species, strain, and sex by using cloned DNA markers

We have detected species, strain, and sex-specific genetic markers for the genus Schistosoma by Southern blot analysis of its DNA using cloned DNA segments of the Schistosoma mansoni ribosomal gene as probes. Restriction analysis of DNA from eight different strains of S. mansoni, from Africa and the Caribbean, revealed that the predominant or major DNA fragment containing the ribosomal gene unit was the same in each but that low copy number or minor fragments containing the gene varied. It was shown that the detection of these minor fragments could serve as the basis for both strain differentiation and the analysis of individual differences within a strain. Analysis of the parents and progeny of a genetic cross revealed sex-linked markers and suggested that these markers are inherited in a Mendelian fashion. DNAs from the species Schistosoma haematobium and Schistosoma japonicum were also analyzed. Differences in the length of the major repeating unit of the ribosomal gene served to distinguish each species. Furthermore, an array of minor bands was detected in each species, suggesting that strains of S. haematobium and S. japonicum could be differentiated in the same manner as S. mansoni strains.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae III. Identification of a mouse strain, P/N, that fails to respond to vaccination

Eleven strains of inbred mice were examined for their ability to develop resistance to challenge Schistosoma mansoni infection as a result of previous exposure to homologous cercariae that had been attenuated by high-dose irradiation. Two strains, C57B1/6J and BALB/c, demonstrated consistently high levels of vaccine-induced immunity (means of 64% and 58% resistance, respectively, when compared to control groups of the same strain) and were designated as 'high responder' strains to vaccination. Six other strains fell into an intermediate category, demonstrating moderate, yet statistically significant, levels of immunity resulting from vaccination (means of 30-50% resistance). Only one of the strains examined consistently failed to respond to vaccination by the development of significant levels of immunity to challenge infection. Animals of the P/N strain demonstrated a mean of only 15% resistance to challenge in five experiments and have been classified as 'low responders' to vaccination. P/N mice have previously been characterized as deficient in their ability to mount delayed hypersensitivity reactions, produce lymphokine and display macrophage activation for cytolysis of extracellular and intracellular targets in other experimental systems, suggesting that these immune responses may be critical to the establishment of vaccine-induced resistance to S. mansoni infection. The availability of high and low responder mouse strains should facilitate a genetic approach to characterization of the immune effector mechanism(s) of vaccine-induced resistance to S. mansoni infection.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. IV. Analysis of the role of IgE antibodies and mast cells

Mice resistant to challenge infection with Schistosoma mansoni by vaccination with highly irradiated cercariae were examined for the presence of circulating IgE antibodies and peritoneal mast cells sensitized against schistosome antigens. Significant levels of SWAP- or CAP-specific IgE antibodies could not be detected by solid phase radioimmunoassay in the sera of C57BL/6 mice during the first 6 wk after vaccination. Similarly, heatlabile antibodies capable of passively sensitizing normal mast cells for degranulation in response to SWAP could not be identified in the same sera. In contrast, peritoneal mast cells harvested from C57BL/6 mice 2 wk or later after vaccination gave strong degranulation responses when challenged with SWAP or CAP. Thus, vaccination with irradiated cercariae induces an unusual form of immediate-type hypersensitivity in which mast cells become sensitized in the absence of detectable circulating IgE antibodies. Mice deficient in mast cells (W/Wv mutant strain) were observed to develop the same resistance to challenge infection after vaccination with irradiated cercariae as nondeficient littermates. Similarly, vaccinated SJL/J mice were found to mount an extremely weak IgE response as measured by mast cell degranulation yet displayed the same level of resistance to challenge infection as other inbred mice developing potent mast cell responses. These findings argue that IgE antibodies and mast cells are not essential components in the effector mechanism of irradiated vaccine-induced immunity against schistosome infection.

Evidence that anti-idiotype induced immunity to experimental African trypanosomiasis is genetically restricted and requires recognition of combining site-related idiotopes

The ability of anti-idiotypic (anti-Id) antibodies to immunize mice against African trypanosomiasis independent of antigen has been confirmed. Of three allogeneic anti-Id antibodies raised against three protective monoclonal antibodies, each with specificity for the variant surface antigen of a clone of Trypanosoma rhodesiense, only one (anti-7H11 Id) was effective in immunizing BALB/c mice against homologous challenge. The immunity was associated with the more rapid and enhanced expression of the corresponding Id after infection. The immunity was restricted to mice bearing genes linked to Igh-Ca, which appeared to control expression of this Id both in response to infection and anti-Id treatment. Another Id, 11D5, appeared to be under similar genetic control. Anti-11D5 Id, however, was ineffective in immunizing mice against infection despite inducing high levels of Id bearing molecules before challenge. The immunizing potential of the respective anti-Id antibodies appeared to be related to the relative concentrations of antibodies reactive with idiotopes near to or within the antigen-combining site, which, in turn, determined the relative proportion of Id-bearing clones activated that had antigen binding activity.

Evidence that anti-idiotype induced immunity to experimental African trypanosomiasis is genetically restricted and requires recognition of combining site-related idiotopes

The ability of anti-idiotypic (anti-Id) antibodies to immunize mice against African trypanosomiasis independent of antigen has been confirmed. Of three allogeneic anti-Id antibodies raised against three protective monoclonal antibodies, each with specificity for the variant surface antigen of a clone of Trypanosoma rhodesiense, only one (anti-7H11 Id) was effective in immunizing BALB/c mice against homologous challenge. The immunity was associated with the more rapid and enhanced expression of the corresponding Id after infection. The immunity was restricted to mice bearing genes linked to Igh-Ca, which appeared to control expression of this Id both in response to infection and anti-Id treatment. Another Id, 11D5, appeared to be under similar genetic control. Anti-11D5 Id, however, was ineffective in immunizing mice against infection despite inducing high levels of Id bearing molecules before challenge. The immunizing potential of the respective anti-Id antibodies appeared to be related to the relative concentrations of antibodies reactive with idiotopes near to or within the antigen-combining site, which, in turn, determined the relative proportion of Id-bearing clones activated that had antigen binding activity.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. IV. Analysis of the role of IgE antibodies and mast cells

Mice resistant to challenge infection with Schistosoma mansoni by vaccination with highly irradiated cercariae were examined for the presence of circulating IgE antibodies and peritoneal mast cells sensitized against schistosome antigens. Significant levels of SWAP- or CAP-specific IgE antibodies could not be detected by solid phase radioimmunoassay in the sera of C57BL/6 mice during the first 6 wk after vaccination. Similarly, heatlabile antibodies capable of passively sensitizing normal mast cells for degranulation in response to SWAP could not be identified in the same sera. In contrast, peritoneal mast cells harvested from C57BL/6 mice 2 wk or later after vaccination gave strong degranulation responses when challenged with SWAP or CAP. Thus, vaccination with irradiated cercariae induces an unusual form of immediate-type hypersensitivity in which mast cells become sensitized in the absence of detectable circulating IgE antibodies. Mice deficient in mast cells (W/Wv mutant strain) were observed to develop the same resistance to challenge infection after vaccination with irradiated cercariae as nondeficient littermates. Similarly, vaccinated SJL/J mice were found to mount an extremely weak IgE response as measured by mast cell degranulation yet displayed the same level of resistance to challenge infection as other inbred mice developing potent mast cell responses. These findings argue that IgE antibodies and mast cells are not essential components in the effector mechanism of irradiated vaccine-induced immunity against schistosome infection.

Evidence that schistosome MHC antigens are not synthesized by the parasite but are acquired from the host as intact glycoproteins

Schistosoma mansoni schistosomula recovered from the lungs of mice have previously been shown to express serologically detectable products of the major histocompatibility complex (MHC). To determine whether these determinants are products of the schistosome genome, DNA from cercariae and adult worms of the parasite was probed with a 32P-cDNA clone encoding a human class I MHC antigen. Although this probe hybridized to mouse DNA, no hybridization was observed with DNA isolated from schistosomes, indicating that there are no DNA sequences homologous to class I MHC antigens in the parasite genome. The class I MHC antigens found on schistosomes were characterized in a further series of experiments. Two monoclonal antibodies known to recognize spatially distinct determinants of H-2Kk both bound to lung-stage schistosomula recovered from mice expressing this haplotype, suggesting that a significant portion of the H-2K molecule is present at the larval surface. Furthermore, both antibodies precipitated from lysates of 125I-lactoperoxidase-labeled lung-stage schistosomula, a molecule of approximately 45,000 daltons similar in mobility to H-2Kk precipitated from 125I-labeled mouse spleen cells. These results support the hypothesis that the class I MHC antigens expressed on S. mansoni are not synthesized by the parasite but are acquired from the host as intact glycoproteins.

Resistance to macrophage-mediated killing as a factor influencing the pathogenesis of chronic cutaneous leishmaniasis

Cutaneous leishmaniasis can be either a spontaneously healing or chronic disease, depending upon the strain of parasite and the immunological status of the host. We have investigated parasite factors responsible for the variable pathogenesis observed in leishmanial infections by testing the sensitivity of several leishmanial strains to intracellular killing in lymphokine (LK) activated mouse macrophages. Significant microbicidal activity against Leishmania tropica, a strain which heals in C57BL/6 (B6) mice, was found. In contrast, a strain (Maria) which has previously been shown to induce chronic nonhealing cutaneous lesions in B6 mice was resistant to killing in activated macrophages. This resistance to killing was observed in macrophages activated by LK obtained from either Bacille Calmette-Guérin-, L. tropica, or the Maria strain infected mice. The inability of LK activated macrophages to kill the Maria strain was shown not to be due to parasite induced inhibition of killing mechanisms, since Maria strain infected, LK treated macrophages exhibited tumoricidial activity similar to uninfected macrophages. Furthermore, LK activated macrophages simultaneously infected with the Maria strain and another intracellular pathogen, Toxoplasma gondii, killed Toxoplasma, but not the Maria strain. Temperature was also found to significantly influence the multiplication and killing of Leishmania parasites. As would be expected from their cutaneous nature, L. tropica and Maria strain parasites multiplied better at 35 degrees C than at 37 degrees C. Also consistent with the failure of cutaneous strains to visceralize in immunocompetent mice was the observation that the killing of leishmanial parasites was enhanced at the higher temperature. Thus, the temperature dependent growth capacity and sensitivity to killing of a given leishmanial strain in macrophages may be important factors influencing the pathogenesis of cutaneous leishmaniasis.

Evidence that schistosome MHC antigens are not synthesized by the parasite but are acquired from the host as intact glycoproteins

Schistosoma mansoni schistosomula recovered from the lungs of mice have previously been shown to express serologically detectable products of the major histocompatibility complex (MHC). To determine whether these determinants are products of the schistosome genome, DNA from cercariae and adult worms of the parasite was probed with a 32P-cDNA clone encoding a human class I MHC antigen. Although this probe hybridized to mouse DNA, no hybridization was observed with DNA isolated from schistosomes, indicating that there are no DNA sequences homologous to class I MHC antigens in the parasite genome. The class I MHC antigens found on schistosomes were characterized in a further series of experiments. Two monoclonal antibodies known to recognize spatially distinct determinants of H-2Kk both bound to lung-stage schistosomula recovered from mice expressing this haplotype, suggesting that a significant portion of the H-2K molecule is present at the larval surface. Furthermore, both antibodies precipitated from lysates of 125I-lactoperoxidase-labeled lung-stage schistosomula, a molecule of approximately 45,000 daltons similar in mobility to H-2Kk precipitated from 125I-labeled mouse spleen cells. These results support the hypothesis that the class I MHC antigens expressed on S. mansoni are not synthesized by the parasite but are acquired from the host as intact glycoproteins.

Identification of surface antigens of schistosomula of Schistosoma mansoni recognized by antibodies from mice immunized by chronic infection and by exposure to highly irradiated cercariae

Surface components of mechanically transformed schistosomula of Schistosoma mansoni were labeled by lactoperoxidase-catalyzed iodination. After solubilization with Triton X-100, antigens were identified by immunoprecipitation. Serum from chronically infected Swiss mice reproducibly precipitated seven major polypeptides with approximate molecular weights (X 10(3] of 94, 68, 45, 40 to 32, 22, and 16. The antigens of molecular weights (X 10(3] of 94, 40 to 32, 22, and 16 were shown to be exposed on the parasite surface by interaction of the antibodies with intact labeled schistosomula. Sera from several strains of infected inbred mice precipitated the same polypeptides. The antibodies produced during chronic infection were found to be stimulated by adult worms since sera from 6-week-infected animals precipitated none of the surface antigens, and the pattern produced by precipitation with antibodies from a mouse infected with male worms only was indistinguishable from the pattern obtained with sera from mice with bisexual infections. Antibodies from mice immunized with highly irradiated cercariae reproducibly precipitated major polypeptides of approximately (X 10(3] 94, 68, 45, 32, 22, 19, and 15 daltons. The antigens of (X 10(3] 94, 43, 32, 22, and 15 daltons were shown to be exposed on the parasite surface by interaction of the antibodies with intact labeled schistosomula. The 15 X 10(3)-dalton surface protein was recognized by sera from vaccinated, but not chronically infected, mice, suggesting that it represents a stage-specific immunogen present on schistosomula but not on adult worms. Sera from two inbred strains of mice which develop different degrees of immunity recognized the same antigens.

Resistance to macrophage-mediated killing as a factor influencing the pathogenesis of chronic cutaneous leishmaniasis

Cutaneous leishmaniasis can be either a spontaneously healing or chronic disease, depending upon the strain of parasite and the immunological status of the host. We have investigated parasite factors responsible for the variable pathogenesis observed in leishmanial infections by testing the sensitivity of several leishmanial strains to intracellular killing in lymphokine (LK) activated mouse macrophages. Significant microbicidal activity against Leishmania tropica, a strain which heals in C57BL/6 (B6) mice, was found. In contrast, a strain (Maria) which has previously been shown to induce chronic nonhealing cutaneous lesions in B6 mice was resistant to killing in activated macrophages. This resistance to killing was observed in macrophages activated by LK obtained from either Bacille Calmette-Guérin-, L. tropica, or the Maria strain infected mice. The inability of LK activated macrophages to kill the Maria strain was shown not to be due to parasite induced inhibition of killing mechanisms, since Maria strain infected, LK treated macrophages exhibited tumoricidial activity similar to uninfected macrophages. Furthermore, LK activated macrophages simultaneously infected with the Maria strain and another intracellular pathogen, Toxoplasma gondii, killed Toxoplasma, but not the Maria strain. Temperature was also found to significantly influence the multiplication and killing of Leishmania parasites. As would be expected from their cutaneous nature, L. tropica and Maria strain parasites multiplied better at 35 degrees C than at 37 degrees C. Also consistent with the failure of cutaneous strains to visceralize in immunocompetent mice was the observation that the killing of leishmanial parasites was enhanced at the higher temperature. Thus, the temperature dependent growth capacity and sensitivity to killing of a given leishmanial strain in macrophages may be important factors influencing the pathogenesis of cutaneous leishmaniasis.

Primidone-induced catatonic schizophrenia

The authors report the case of a severely retarded, 19-year-old female (treated with primidone 250 mg tid since age 12) who was admitted with visual and auditory hallucinations. After four days of continuing hallucinations, she went into classic catatonic schizophrenia. Upon examination, her primidone serum level was found to be well above the normal therapeutic range. The primidone dosage was decreased, and symptoms subsided as serum levels returned to normal.

The exposed carbohydrates of schistosomula of Schistosoma mansoni and their modification during maturation in vivo

Lectins labeled with 125I or conjugated with fluorescein were employed to study the carbohydrates on the surface of different stages of schistosomula of Schistosoma mansoni. Newly transformed schistosomula were shown to bind concanavalin A; the 60 000 and 120 000 dalton agglutinins from Ricinus communis; the fucose-binding protein from Lotus tetragonolobus; wheat germ agglutinin and peanut agglutinin. Soybean agglutinin, Ulex europaeus agglutinin and Dolichos biflorus agglutinin, on the other hand, failed to bind to the schistosomulum surface. The binding of peanut and soybean agglutinin was unaffected by pretreatment of the parasites with neuraminidase. Binding of concanavalin A, the 120 000 dalton agglutinin from Ricinus communis, wheat germ agglutinin and peanut agglutinin to the surface of 5-day schistosomula, recovered from the lungs of mice, was also demonstrated. In each case, however, the level of binding was approximately 70% less than that observed with newly transformed schistosomula and the binding of the fucose-binding protein from L. tetragonolobus practically disappeared. In contrast with newly transformed schistosomula, lung stage schistosomula, pretreated with neuraminidase, displayed a significant increase in the binding of peanut and soybean agglutinin. The results indicate that a significant alteration in the surface carbohydrates of S. mansoni occurs during in vivo maturation of the parasite. This change may contribute to the organism's ability to survive in the vertebrate host.

Incubation in mice provides a signal for the differentiation of Trypanosoma cruzi epimastigotes to trypomastigotes

The differentiation of Trypanosoma cruzi epimastigotes into trypomastigotes was studied in diffusion chambers subcutaneously implanted in mice. Using epimastigotes of the Tulahuén strain, transformation was first evident at 16 h after implantation and reached its maximum (92% trypomastigotes) by 24 h. Shortly before their differentiation into trypomastigotes, epimastigotes were found to develop resistance to lysis by the alternative pathway of complement. Furthermore, implantation of stationary-phase (as opposed to log-phase) parasites resulted in the accumulation of large numbers of complement-resistant epimastigotes in the chambers. These observations suggest that epimastigotes pass through a complement-resistant transitional stage before differentiating into trypomastigotes and that transformation may require cell division. In a further series of experiments, epimastigotes recovered 7 h after implantation in mice were found to differentiate into trypomastigotes when cultured in vitro for an additional 17 h at 37 degrees C. This observation indicates that the events which trigger the morphologic transformation of epimastigotes into trypomastigotes can be dissociated operationally from the differentiation process itself.

Lack of resistance to Schistosoma japonicum in mice immunized with irradiated S. mansoni cercariae

Mice immunized with irradiated Schistosoma mansoni cercariae were resistant to challenge with S. mansoni cercariae (mean resistance 53%) but not to challenge with S. japonicum cercariae (mean resistance -5%). Furthermore, the antibodies induced by vaccination with irradiated S. mansoni cercariae were more reactive with S. mansoni than with S. japonicum schistosomula. These results support the concept that the resistance induced by vaccination with irradiated cercariae is immunologically specific.

The genome of Schistosoma mansoni: isolation of DNA, its size, bases and repetitive sequences

DNA has been prepared from adults and cercariae of Schistosoma mansoni utilizing a technique that involves centrifugation through cesium chloride. The DNA isolated from S. mansoni adults and that isolated from cercariae were found to be indistinguishable in all analyses. No modified bases were detected by chromatography or comparative endonuclease restriction. Cot analysis demonstrated that the haploid genome of S. mansoni is 0.26 pg (2.7 X 10(8) base pairs) and that the genome contains both moderately and highly repeated components. Some of the repetitive fraction of DNA consists of tandemly repeated ribosomal genes of which there are 500-1000 copies per genome (1.8-3.6% of the total DNA). Four other non-ribosomal repetitive sequences (comprising at least a further 2.0% of the total DNA) have been isolated from a DNA clone bank and their arrangement within the S. mansoni genome investigated by restriction and Southern blot analysis. These cloned segments of DNA appear in many different locations within the genome and thus are reminiscent of the interspersed DNA sequences described in higher eukaryotic organisms.

Immunization of mice against African trypanosomiasis using anti-idiotypic antibodies

Anti-idiotypic (anti-Id) antibodies were raised against three protective monoclonal antibodies, each with specificity for the variable antigen type (VAT) of a clone of Trypanosoma rhodesiense. The IgG1 fractions of each were pooled and administered to BALB/c mice 3-4 wk before homologous challenge. The course of primary parasitemia was altered in 19 of 30 anti-Id-treated animals. The immunity was manifested as either: (a) complete protection, (b) reduced parasitemia, or (c) selection against parasites bearing the original VAT. The three idiotypes (Id) were found in variable levels in serum during the course of infection in control animals. However, in all anti-Id-treated mice that displayed immunity, one Id in particular (7H11) was detectable much earlier in infection and in higher levels than in control mice or anti-Id-treated, nonimmune mice. Six of nine mice treated with the anti-7H11 Id alone also displayed immunity, manifested in this case exclusively as selection against parasites bearing the original VAT. The effect was again associated with the more rapid appearance of the Id after infection. Specificity of the anti-Id-induced immunity was supported by the failure of anti-7H11 Id treatment to alter the course of infection with a heterologous clone of T. rhodesiense. To our knowledge, this is the first report of the antigen-independent induction of antimicrobial immunity using anti-Id antibodies.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. II. Analysis of immunity in hosts deficient in T lymphocytes, B lymphocytes, or complement

Laboratory mice with genetic or induced immunodeficiencies were vaccinated with irradiated cercariae of Schistosoma mansoni and assayed 4 wk later for their resistance to challenge infection. Athymic nude mice failed to develop immunity to challenge or detectable antibody responses to schistosomula, whereas heterozygote (nu/+) controls and nude mice with thymus grafts displayed highly significant levels of resistance and anti-schistosomulum antibody. Similarly, no resistance or antibody production as observed in vaccinated mice that had been made deficient in B lymphocytes by the injection of anti-mu-chain antisera from birth. In contrast, normal levels of vaccine-induced resistance were observed in mice genetically deficient in the fifth component of complement (C5) and in mice decomplemented before challenge by treatment with cobra venom factor. These results indicate that the resistance to challenge infection induced by irradiated cercariae is both thymus and B lymphocyte dependent and therefore is likely to result from specific immune responses directed against schistosome worms. The data also argue against a role for complement in the effector mechanism of vaccine-induced immunity.

Macrophages as effector cells of protective immunity in murine schistosomiasis. III. Loss of susceptibility to macrophage-mediated killing during maturation of S. mansoni schistosomula from the skin to the lung stage

Newly transformed skin-stage and lung-stage schistosomula were compared in terms of their susceptibility to killing mediated by activated mouse macrophages in vitro. Although skin-stage schistosomula were readily killed by macrophages activated as a consequence of either BCG or Schistosoma mansoni infection and used either as cell monolayers or in suspension, lung-stage larvae appeared to be totally resistant to this effector mechanism and survived normally when reinjected into mice. Resistance of schistosomula to in vitro damage by macrophages was evident as early as 18 hr after host infection and was complete in worms recovered at 42 hr. The insusceptibility of lung-stage larvae is apparently not due to a defect in effector cell-target contact, because the induction of extensive macrophage adherence to the worms by the addition of anti-mouse red blood cell antisera to the cultures had no effect on parasite viability. These findings provide additional support for the concept that schistosomula during their development to the lung stage undergo a generalized change affecting their susceptibility to a variety of different immunologic effector mechanisms.

Macrophages as effector cells of protective immunity in murine schistosomiasis. II. Killing of newly transformed schistosomula in vitro by macrophages activated as a consequence of Schistosoma mansoni infection

Plastic adherent peritoneal cells from Schistosoma mansoni-infected mice have previously been shown to exhibit nonspecific tumoricidal activity in vitro. In this report we show that these same cell populations kill significant numbers of skin-stage schistosomula in vitro in the absence of added antibody. Larval killing by these activated cells could be enhanced by the use of suspension rather than monolayer cultures and by addition of heat-inactivated immune mouse serum to the cultures. Adherence of cells to schistosomula was also enhanced under the same conditions, suggesting that cell binding to the larvae might be critical in the development or expression of microbicidal activity. In support of this hypothesis, the same level of enhancement of cell binding and larval damage was observed upon substitution of concanavalin A for immune mouse serum. Killing of schistosomula appeared to be mediated solely by activated macrophages in the peritoneal cell suspensions from S. mansoni-infected mice, because partially purified preparations of eosinophils were virtually inactive in these assays. Likewise, inflammatory macrophages from uninfected mice were unable to kill schistosomula under the same conditions, emphasizing the importance of activation in the development of killing capability. The finding that macrophages activated as a consequence of S. mansoni infection are able to kill larval schistosomes in vitro suggests that these cells may play a role in concomitant immunity to schistosomiasis in vivo.

Macrophages as effector cells of protective immunity in murine schistosomiasis. II. Killing of newly transformed schistosomula in vitro by macrophages activated as a consequence of Schistosoma mansoni infection

Plastic adherent peritoneal cells from Schistosoma mansoni-infected mice have previously been shown to exhibit nonspecific tumoricidal activity in vitro. In this report we show that these same cell populations kill significant numbers of skin-stage schistosomula in vitro in the absence of added antibody. Larval killing by these activated cells could be enhanced by the use of suspension rather than monolayer cultures and by addition of heat-inactivated immune mouse serum to the cultures. Adherence of cells to schistosomula was also enhanced under the same conditions, suggesting that cell binding to the larvae might be critical in the development or expression of microbicidal activity. In support of this hypothesis, the same level of enhancement of cell binding and larval damage was observed upon substitution of concanavalin A for immune mouse serum. Killing of schistosomula appeared to be mediated solely by activated macrophages in the peritoneal cell suspensions from S. mansoni-infected mice, because partially purified preparations of eosinophils were virtually inactive in these assays. Likewise, inflammatory macrophages from uninfected mice were unable to kill schistosomula under the same conditions, emphasizing the importance of activation in the development of killing capability. The finding that macrophages activated as a consequence of S. mansoni infection are able to kill larval schistosomes in vitro suggests that these cells may play a role in concomitant immunity to schistosomiasis in vivo.

Macrophages as effector cells of protective immunity in murine schistosomiasis. III. Loss of susceptibility to macrophage-mediated killing during maturation of S. mansoni schistosomula from the skin to the lung stage

Newly transformed skin-stage and lung-stage schistosomula were compared in terms of their susceptibility to killing mediated by activated mouse macrophages in vitro. Although skin-stage schistosomula were readily killed by macrophages activated as a consequence of either BCG or Schistosoma mansoni infection and used either as cell monolayers or in suspension, lung-stage larvae appeared to be totally resistant to this effector mechanism and survived normally when reinjected into mice. Resistance of schistosomula to in vitro damage by macrophages was evident as early as 18 hr after host infection and was complete in worms recovered at 42 hr. The insusceptibility of lung-stage larvae is apparently not due to a defect in effector cell-target contact, because the induction of extensive macrophage adherence to the worms by the addition of anti-mouse red blood cell antisera to the cultures had no effect on parasite viability. These findings provide additional support for the concept that schistosomula during their development to the lung stage undergo a generalized change affecting their susceptibility to a variety of different immunologic effector mechanisms.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. II. Analysis of immunity in hosts deficient in T lymphocytes, B lymphocytes, or complement

Laboratory mice with genetic or induced immunodeficiencies were vaccinated with irradiated cercariae of Schistosoma mansoni and assayed 4 wk later for their resistance to challenge infection. Athymic nude mice failed to develop immunity to challenge or detectable antibody responses to schistosomula, whereas heterozygote (nu/+) controls and nude mice with thymus grafts displayed highly significant levels of resistance and anti-schistosomulum antibody. Similarly, no resistance or antibody production as observed in vaccinated mice that had been made deficient in B lymphocytes by the injection of anti-mu-chain antisera from birth. In contrast, normal levels of vaccine-induced resistance were observed in mice genetically deficient in the fifth component of complement (C5) and in mice decomplemented before challenge by treatment with cobra venom factor. These results indicate that the resistance to challenge infection induced by irradiated cercariae is both thymus and B lymphocyte dependent and therefore is likely to result from specific immune responses directed against schistosome worms. The data also argue against a role for complement in the effector mechanism of vaccine-induced immunity.

Decreasing immunogenicity of developing schistosome larvae

Cercariae, skin stage schistosomula, and lung stage schistosomula of Schistosoma mansoni were attenuated by gamma irradiation and tested for their ability to induce protective immunity against cercarial challenge in C57Bl/6J mice. The highest levels of resistance were induced by cercariae administered either percutaneously or intramuscularly. Skin stage schistosomula inoculated intramuscularly gave less protection while lung stage schistosomula from syngeneic donors were the least immunogenic. A similar ranking in immunogenicity was observed when the anti-skin stage schistosomular antibody responses induced by the different parasite stages were compared. In contrast, none of the immunization protocols were found to stimulate antibodies capable of recognizing lung stage schistosomula. These results suggest that, as schistosome larvae mature from the cercarial to the lung stage, they undergo a substantial loss in immunogenicity. This change may help explain the failure of older larvae to be immunologically destroyed in infected hosts.

Enhanced resistance to acute infection with Trypanosoma cruzi in mice treated with an interferon inducer

For an exploration of the effects of interferon-inducible resistance mechanisms in acute American trypanosomiasis, the synthetic interferon inducer tilerone hydrochloride was administered to mice of the C57BL/6J strain, which is highly resistant to Trypanosoma cruzi, 18 to 24 h before infection with a potentially lethal dose of bloodstream trypomastigotes. Although all of the control mice died within 30 days of the acute infection, approximately 50% of the tilerone-treated animals were able to survive indefinitely (P less than 0.05). The tilerone-treated mice demonstrated significant levels of serum interferon and splenic natural killer cells at the time of infection. Macrophages isolated from the peritoneal cavities of tilerone-treated C57BL/6J mice appeared to kill significant numbers of trypanosomes during 2 to 3 days of in vitro culture, indicating that activated macrophages may contribute to the enhanced resistance to T. cruzi infection in these mice. Beige mice treated with tilerone did not survive T. cruzi infection as well as tilerone-treated heterozygotes did, suggesting a role for natural killer cells in interferon-induced resistance. These results suggest that interferon or effector mechanisms enhanced by interferon induction can play a significant role in influencing resistance to T. cruzi infection.

Cytotoxicity of cytosine arabinoside on mouse progenitor stem cells

In vitro colonogenic assay of mouse marrow granulocytic progenitor cells (spleen and agar colony forming cells) was carried out to determine the cytotoxic effect of 1-B-D-arabinofuranosyl cytosine on granulopoiesis. Mainly, the drug cytotoxicity on progenitor cells depended upon exposure time. Endotoxin stimulated colony forming cells showed enhanced cytotoxicity with shorter (25 min) exposure time as compared to a longer exposure of 60 min. A 60 min exposure was found to give maximum cytotoxic effect on spleen colony forming cells. With prolonged incubation, the cytotoxic effect of the drug on spleen colony forming and agar colony forming cells was more or less the same. Incubation of granulocytic precursor cells with the cytotoxic drug, in vitro, produced effects similar to those previously reported with in vivo drug administration. Therefore, some of these techniques can be employed as improved screening models for evaluating the cytotoxic agents in clinical trials.

Light and electron microscopic appearance of rat peritoneal mast cells adhering to schistosomula of Schistosoma mansoni by means of complement or antibody

Metrizamide-gradient purified rat peritoneal mast cells were allowed to adhere to schistosomula of S. mansoni that had been preincubated in either minimum essential medium with 5% fetal calf serum (MEM/FCS), heat-inactivated serum from rats 8 weeks after cercarial infection (IRS) fresh normal rat serum as a source of complement (NRS), or IRS and NRS. Adherence was evaluated in sections 0.3 micrometers thick. The preincubation conditions favoring cell adherence were IRS + NRS greater than NRS greater than IRS greater than MEM/FCS. Greater adherence was seen at 60 min than at 10 min. Discharge of mast cell granulates was seen infrequently, was not greater in adherent than nonadherent cells, was not increased by any preincubation condition, and did not occur against the parasite's surface, as would be expected if antigen, antibody, and surface receptors were aggregated there. Electron microscopic examination showed that attachment to the parasite occurred through electron-dense material which was usually fibrillar in appearance. Membrane fusion, such as is seen between human neutrophils and schistosomula, did not occur.

Activation of the alternative complement pathway by Trichomonas vaginalis

The mechanism underlying the lysis of Trichomonas vaginalis by normal human or guinea pig serum was investigated. The involvement of the complement system was demonstrated by the failure of human serum deficient in C3 or C8 to mediate parasite killing and by the ablation of lytic activity observed when fresh sera were heated at 56 degrees C or treated with ethylenediaminetetraacetate. Fixation of human C3 on the parasite surface was demonstrated by indirect immunofluorescence. The involvement of the alternative complement pathway was demonstrated (i) by the inability of properdin-depleted human serum to lyse T. vaginalis and (ii) by the normal killing observed with guinea pig serum lacking C4 and with normal human or guinea pig serum treated with ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid and Mg2+ to selectively inhibit the classical pathway.

Immunogenicity of haptenated schistosomula in vitro

Skin-stage schistosomula of Schistosoma mansoni modified with 2,4,6-trinitrophenyl (TNP) induce primary anti-TNP plaque-forming cell (PFC) responses in normal mouse spleen cells in vitro. The PFC are TNP-specific, and the response is dependent on adherent cells and T lymphocytes. In contrast, comparably haptenated lung stage larvae are weakly or nonimmunogenic in this system, and their inability to stimulate anti-TNP PFC cannot be attributed to a toxic or suppressive effect. These observations suggest that maturation of schistosomula in vivo is accompanied by a decline in their immunogenicity, which, along with other adaptive mechanisms, may promote the survival of parasites in the host environment.

The response of mice immune to Schistosoma mansoni to a challenge infection which bypasses the skin: evidence for two mechanisms of immunity

Mice which had developed immunity to reinfection with Schistosoma mansoni following exposure to 20 cercariae and mice which had been immunized against S. mansoni by exposure to 400 highly irradiated (20 krad) cercariae, were tested for their ability to resist a percutaneous cercarial challenge and an intravenous challenge with 5-day-old lung-stage schistosomula derived from the same cercariae. Although both types of immune mice showed a marked resistance to a cercarial challenge, only the infected mice showed a comparable immunity to an intravenous challenge with lung schistosomula. These results confirm earlier studies which suggest that the major attrition of a cercarial challenge in infected mice occurs at the post-lung stage, whilst the attrition of a challenge infection in mice immunized with highly irradiated cercariae takes place in the skin. They provide further evidence for two separate mechanisms of immunity against S. mansoni in mice.

Studies of the antibody-dependent killing of schistosomula of Schistosoma mansoni employing haptenic target antigens. II. In vitro killing of TNP-schistosomula by human eosinophils and neutrophils

Purified human eosinophils and neutrophils were compared for their capacity to mediate anti-TNP antibody-dependent killing of schistosomula of Schistosoma mansoni surface labeled with TNBS. In contrast with findings from studies employing human anti-schistosome sera and unmodified larvae, neutrophils in addition to eosinophils were found to be potent killers of schistosomula. Indeed, neutrophils proved to be consistently more effective than eosinophils in killing haptenated larvae throughout the dose response of each of the components (i.e., the TNBS surface label, rabbit anti-TNP sera and cells) of the in vitro reaction. The capacity of neutrophils to kill haptenated parasites is not likely to be due to the use of rabbit antibodies in the assays, since these cells were ineffective in killing unlabeled schistosomula when either rabbit or human anti-schistosome sera were employed. Furthermore, the ability of neutrophils to destroy TNP-labeled schistosomula does not appear to result from sublethal damage induced by the labeling procedure, since haptenated parasites were found to be no more susceptible than unmodified worms to killing mediated by anti-schistosome sera plus eosinophils or complement and, like unlabeled parasites, could not be killed by anti-schistosome sera plus neutrophils. The lethal interaction of neutrophils and haptenated schistosomula was preceded by a rapid and marked adherence of the cells to the worms, an effect that was not observed in the nonlethal interaction of neutrophils with schistosomula induced by anti-schistosome sera. The results argue, therefore, that the capacity of different granulocyte populations to kill schistosomula may be determined by the kinetics and intensity with which the effector cells adhere to the parasites. The findings further suggest that a key factor influencing the differential adherence of the cells to the parasites and their subsequent death may be the nature of the specific antigen-antibody interaction occurring at the surface of the larvae.

Studies of the antibody-dependent killing of schistosomula of Schistosoma mansoni employing haptenic target antigens. II. In vitro killing of TNP-schistosomula by human eosinophils and neutrophils

Purified human eosinophils and neutrophils were compared for their capacity to mediate anti-TNP antibody-dependent killing of schistosomula of Schistosoma mansoni surface labeled with TNBS. In contrast with findings from studies employing human anti-schistosome sera and unmodified larvae, neutrophils in addition to eosinophils were found to be potent killers of schistosomula. Indeed, neutrophils proved to be consistently more effective than eosinophils in killing haptenated larvae throughout the dose response of each of the components (i.e., the TNBS surface label, rabbit anti-TNP sera and cells) of the in vitro reaction. The capacity of neutrophils to kill haptenated parasites is not likely to be due to the use of rabbit antibodies in the assays, since these cells were ineffective in killing unlabeled schistosomula when either rabbit or human anti-schistosome sera were employed. Furthermore, the ability of neutrophils to destroy TNP-labeled schistosomula does not appear to result from sublethal damage induced by the labeling procedure, since haptenated parasites were found to be no more susceptible than unmodified worms to killing mediated by anti-schistosome sera plus eosinophils or complement and, like unlabeled parasites, could not be killed by anti-schistosome sera plus neutrophils. The lethal interaction of neutrophils and haptenated schistosomula was preceded by a rapid and marked adherence of the cells to the worms, an effect that was not observed in the nonlethal interaction of neutrophils with schistosomula induced by anti-schistosome sera. The results argue, therefore, that the capacity of different granulocyte populations to kill schistosomula may be determined by the kinetics and intensity with which the effector cells adhere to the parasites. The findings further suggest that a key factor influencing the differential adherence of the cells to the parasites and their subsequent death may be the nature of the specific antigen-antibody interaction occurring at the surface of the larvae.

Immunogenicity of haptenated schistosomula in vitro

Skin-stage schistosomula of Schistosoma mansoni modified with 2,4,6-trinitrophenyl (TNP) induce primary anti-TNP plaque-forming cell (PFC) responses in normal mouse spleen cells in vitro. The PFC are TNP-specific, and the response is dependent on adherent cells and T lymphocytes. In contrast, comparably haptenated lung stage larvae are weakly or nonimmunogenic in this system, and their inability to stimulate anti-TNP PFC cannot be attributed to a toxic or suppressive effect. These observations suggest that maturation of schistosomula in vivo is accompanied by a decline in their immunogenicity, which, along with other adaptive mechanisms, may promote the survival of parasites in the host environment.

Schistosomiasis: immunologic properties of developing schistosomula

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Cell-mediated cytotoxicity to Trypanosoma cruzi. II. Antibody-dependent killing of bloodstream forms by mouse eosinophils and neutrophils

Mouse mononuclear cells, neutrophils, and eosinophils were tested for their capacity to mediate antibody-dependent cytotoxicity against bloodstream trypomastigotes of Trypanosoma cruzi. Granulocyte populations were found to be far more effective than nonadherent mononuclear cells in an in vitro assay in which the number of motile parasites was measured. Eosinophils and neutrophils were observed to be equally efficient on a cell-per-cell basis in killing the trypomastigotes. These results were verified in parallel experiments in which trypomastigotes, after incubation with antibody and effector cells, were reinjected into susceptible mice and the survival of the animals was determined.

Transformation of hemopoietic stem cells by phytohemagglutinin (PHA) II. Mechanism of action

It has long been known that phytohemagglutinin (PHA) stimulates transformation and growth of immune competent lymphocytes. Lymphoid cell colonies have previously been shown in the spleen with PHA treated lymph node cells from donor mice were injected into irradiated mice. This communication reports the results of in vivo effects of PHA stimulation on agar colony forming units and spleen colony forming units (CFU). C3H/Hej mice injected with 1 ml of PHA-M were found to secrete colony stimulating factors (PHA-CSF) which lead to an increase in the number of agar colony forming units (granulopoiesis). Serum obtained on day 6 after PHA injection showed enhanced granulopoiesis which was four times higher than in the controls. It was found that 1.0 ml and 0.15 ml of PHA-CSF were more effective in promoting the growth of agar colony forming units in agar plates. Intravenous injection of PHA increased the number of spleen-as well as agar colony forming units (CFU). Day 3 appeared to be optimal for in vivo effects of PHA on granulopoietic cells. An increase in the colony forming units was obtainable when previously treated bone marrow and spleen cells taken on day 3 were injected into irradiated mice. There was a fourfold increase of the colony forming units (CFUs) in the spleen and a twofold one in bone marrow cells. As compared to the controls, the increase in agar colony forming units (CFUc) of bone marrow was fourfold and that of the spleen tenfold. On day 5 some effect was still noticeable but it was lower than on day 3. On weight and cell count basis it was found that on day 6 PHA had a significant in vivo effect on the spleen. On the basis of our findings it can be concluded that PHA supports the survival of transplanted stem cells by stimulating their differentiation into unipotent erythroid progenitor cells. It may also be concluded that PHA activates the immune competent stem cells (mostly T lymphocytes) and displays a supporting function for a better stem cell survival and differentiation into the erythroid progenitor cells. The activated lymphocytes secrete a colony-stimulating like factor which stimulates granulopoiesis and also helps in the differentiation of the stem cells.

Enzymatic treatment transforms trypomastigotes of Trypanosoma cruzi into activators of alternative complement pathway and potentiates their uptake by macrophages

In the absence of bound antibody, trypomastigote bloodstream forms of Trypanosoma cruzi fail to activate the alternative complement pathway. We now demonstrate that treatment with trypsin and, to a lesser extent, with sialidase converts these protozoa into activators of the pathway, as judged by their lysis in normal sera or sera genetically deficient in fourth or second component of complement (C4 or C2) and their Mg2+-dependent consumption of C3 as measured by crossed immunoelectrophoresis. In addition, after pretreatment with enzyme and incubation in C5-deficient serum, trypomastigotes were shown to possess both C3 and properdin factor B (B) on their surface as judged by immunofluorescence. Requirement for the late components C5-C9 was suggested by the failure of C5-deficient sera to lyse trypsin-treated parasites. The inability to activate the alternative complement pathway was regained by these organisms after incubation in vitro. This restoration of insusceptibility was inhibited when puromycin was included in the culture medium. Treatment of the trypomastigotes with trypsin also potentiated their uptake by mouse peritoneal macrophages without apparent interference with their capacity to differentiate and multiply inside the cell. These findings suggest that untreated trypomastigotes normally escape recognition by the alternative pathway in vivo because of the presence on their surface of trypsin- and sialidase-sensitive regulatory molecules, the expression of which is dependent on protein synthesis.