T-cell Deprived Mice Research Articles

Immune-dependent thrombocytopaenia in mice infected with Schistosoma mansoni.

As has been shown previously, immunologically intact mice with patent Schistosoma mansoni infections had a significantly lower mean platelet number than intact uninfected mice (P<0.0001). However, platelet numbers in T-cell deprived mice with patent infections were not significantly different from those in uninfected T-cell deprived mice. Also, platelet counts in both the infected and uninfected T-cell deprived groups were not significantly different from those in intact uninfected mice. The S. mansoni-induced thrombocytopaenia in mice is thus seemingly immune dependent. Immunologically intact mice with chronic 12-week-old S. mansoni infections had IgG antibodies that were reactive in an ELISA-type assay with whole fixed platelets of both mouse and human origin. In Western immunoblots the IgG antibodies from chronically-infected mice reacted in particular against mouse and human platelet antigens of 90, 37 and 30 kDa. Antisera raised from 2 rabbits, immunized respectively with mouse and human platelet antigens, cross-reacted with antigens of the larval, adult worm and egg stages of S. mansoni. These results support the hypothesis that an anti-platelet antibody response may be the cause of the thrombocytopaenia observed in mice with patent schistosome infections.

Immune attrition of adult schistosomes

Mouse infection models are described that demonstrate reduction in the rate of egg production in Schistosoma haematobium worms 6-10 weeks after the onset of oviposition and loss of Schistosoma bovis worms around 10 weeks after infection. Neither phenomenon has been shown in Schistosoma mansoni- or Schistosoma japonicum-infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by transference of the ability to reduce a S. bovis worm burden in immuno-compromised hosts with immune serum. Vaccination with irradiation-attenuated parasites of S. haematobium was also shown to have consequences for the adults of challenge infections of either S. haematobium or of S. bovis, but not of S. mansoni. Thus, prior vaccination resulted in an abrogation of the reduced egg production by S. haematobium and S. bovis worms and also of the adult worm elimination that occurred in non-vaccinated S. bovis-infected mice. These models are being used to define the targets and mechanisms involved in the attrition of adult worms of schistosomes with terminal spined eggs.

The susceptibility of adult schistosomes to immune attrition.

Mouse infection models are described that demonstrate reduction of egg production in Schistosoma haematobium infections and both worm loss and reduced fecundity in S. bovis infections. Neither phenomenon could be shown in S. mansoni infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by serum transfer of the ability to reduce a S. bovis worm burden into immunocompromised hosts. Vaccination with irradiation attenuated parasites was also shown to have consequences for the adults of a challenge infection of S. haematobium and S. bovis specifically. Prior vaccination resulted in an abrogation of the anti-fecundity and adult worm elimination that occurred in non-vaccinated similarly infected mice. These models are being used to define the targets and mechanisms involved in anti-adult attrition. A serological assay, quantitation of a circulating antigen (CAA) has been assessed for its ability to measure worm burdens of different species of schistosome in mice. This assay will be used to question whether anti-adult immunity contributes to the pattern of infection with S. mansoni and S. haematobium in man.

The effect of cyclosporin A on Trypanosoma musculi infection of mice

Cyclosporin A treatment of mice infected with Trypanosoma musculi mimicked the effect of T-cell deprivation in increasing the parasitemia and lowering the antibody responses. However, in contrast to T-cell deprivation, cyclosporin A treated mice were still able to clear the parasites from the blood. As expected, T-cell deprived mice were not responsive to cyclosporin A. It is suggested that antibodies against T-independent antigens of the parasite are ineffective in promoting elimination of the trypanosomes. These findings support the importance of T-helper cells in the final elimination of T. musculi from the blood of mice.

The response toSchistosoma bovisin normal and T-cell deprived mice

Normal and T-cell deprived mice have been compared in their response to infection with Schistosoma bovis. The deprived mice survived longer than comparably infected, immunologically intact controls, despite an increased longevity of the adult S. bovis worms in the former animals giving rise to higher tissue egg densities. The reduced pathology in deprived mice was due to inhibition of T-cell dependent granuloma formation around tissue-bound schistosome eggs, with concomitantly decreased tissue disruption as evidenced by smaller spleens and lower circulating transaminase concentrations. These observations on S. bovis contrast with the greater morbidity and earlier mortality induced by S. mansoni in T-cell deprived mice, the latter due to an hepatotoxic potential of S. mansoni eggs that is expressed in the absence of the host immune response. The absence of hepatocyte damage around S. bovis eggs in deprived mice indicates that this schistosome lacks such a toxin, and this could explain why during S. bovis infection synthesis of the two acute-phase proteins, complement C3 and serum amyloid P-component (SAP) here seemed less T-dependent than has previously been found during S. mansoni infection of mice. In a time-course experiment the hypergammaglobulinaemia induced by S. bovis, and the specific IgG antibody response against egg antigens were significantly T-cell dependent during the early stages of patency. Similarly, in most experiments assayed once between 9 and 11 weeks after S. bovis infection, deprived mice had significantly reduced hypergammaglobulinaemias, and reduced specific IgM and IgG antibody responses against both worm and egg antigens.

Parasitological observations of Schistosoma bovis in normal and T-cell deprived mice.

A laboratory life-cycle of Schistosoma bovis was established in order to study the host-parasite relationship in immunologically intact and T-cell deprived mice. Normal mice were found to have 'self-cured' their S. bovis infections almost completely by 10 weeks after cercarial administration, and there was no evidence of self-cure by day 79 in T-cell deprived animals. Thus, groups of deprived mice autopsied between 9 and 11 weeks after infection were invariably found to have greater worm burdens and a greater total number of eggs in the liver than comparably-infected normal mice. However, liver egg counts/worm pair were similar in the two types of host, and differences between normal and deprived mice with respect to total S. bovis egg counts in the intestine were also not consistently in the same direction in all experiments. Faecal egg counts were always less in deprived mice than in normal mice, even in an experiment in which the deprived mice had a significantly higher intestinal tissue egg count than the normal control group. The results are discussed in relation to the better known S. mansoni/mouse host-parasite relationship.

Regeneration of spleen colony-forming cells and granulocyte-monocyte progenitors in T-cell deprived mice treated with cyclophosphamide

The role of T cells in regeneration of CFU-S(d8) and GM-CFU was investigated in adult Cy treated mice. CBA mice were deprived of T cells by adult thymectomy and irradiation (TIR) and treated with 200 mg/kg Cy. The type of CFU-S(d8) and GM-CFU regeneration curve after Cy was not different from that found in nonthymectomized, irradiated (NIR) mice. The activity of a stimulator of CFU-S(d8) proliferation was increased to the same degree in the bone marrow of both TIR and NIR mice. However CFU-S(d8) recovered to a higher level in TIR than in NIR mice. The results presented demonstrate that T-cell depletion in adult mice influences CFU-S(d8) growth.

Immunological control of hepatotoxicity and parasite egg excretion in Schistosoma mansoni infections: stage specificity of the reactivity of immune serum in T-cell deprived mice

Within seven weeks of infection with 200 Schistosoma mansoni cercariae, T-cell deprived mice have been shown to suffer from extensive microvesicular damage to hepatocytes, and an inability to excrete parasite eggs at the same rate as comparably infected, immunologically intact controls. Administration of serum (CIS) from chronically infected, immunologically intact donors prevented the development of microvesicular cell damage and partially restored egg excretion rates in infected deprived mice. Serum pools obtained from mice injected either with intact S. mansoni eggs or with a homogenate of eggs emulsified in Freund's complete adjuvant (FCA) were as effective as CIS in preventing hepatotoxicity and restoring the rate of egg excretion in infected deprived recipients. The degree of protection of liver tissue afforded by immune sera could be monitored either by histopathological examination of liver sections or by estimation of serum transaminase concentrations, the results from both assays being generally in agreement. Sera from donor mice injected with cercarial or worm antigens in FCA were relatively inactive either in protecting against S. mansoni-induced liver damage or in reconstituting egg excretion rates in infected deprived mice. Serum from donor mice infected with 25 cercariae became hepato-protective between 49 and 53 days after infection of the donors, and the degree of hepatoprotective activity and egg excretion reconstituting capacity in the serum of 25 cercariae-infected donors was shown to increase between 8 and 16 weeks after infection. Increasing the size of infection of the serum donors to 100 cercariae gave only a marginal increase of hepatoprotective activity at 7 weeks when compared with serum donors infected with 25 cercariae for 7 weeks. Liver parenchymal cells of very heavily infected, immunologically intact mice were found to show microvesicular damage similar to that in livers of infected deprived mice, and administration of CIS to these normal mice was histopathologically protective. However, the elevated serum transaminase concentrations obtaining in the infected normal mice were not reduced to any extent by CIS. The results obtained from serum-reconstituted deprived mice are discussed in terms of the contribution they may make to a better understanding of the host-parasite relationship in immunologically intact mice.

Identification and partial purification of an antigen (ω 1 from Schistosoma mansoni eggs which is putatively hepatotoxic in T-cell deprived mice

T-cell deprived mice heavily infected with Schistosoma mansoni suffer from severe microvesicular damage to hepatocytes within seven weeks of infection. The damage can be prevented by administration of serum (CIS) obtained from mice chronically infected with S. mansoni or from mice immunized with intact or homogenized S. mansoni eggs. Reaction of serum samples from individual chronically infected mice in immunoelectrophoresis with S. mansoni egg homogenate has enabled the identification of at least 12 distinct immuno precipitation reactions. Precipitating antibody against one S. mansoni egg antigen, ω 1, has been detected in all mice with patent chronic infections, and anti- ω 1 antibody is the most concentrated of the precipitating anti-egg antibody species in pooled CIS. Pooled serum obtained from infected intact mice reacting predominantly against ω 1 was found partially to prevent the hepatotoxicity reaction on transfer to infected deprived mice. Serum samples from mice injected with egg homogenate fractionated either by preparative electrophoresis or by cation exchange chromatography, and containing antibodies reactive with antigen ω 1 in immuno-precipitation, were fully protective against liver cell damage induced by S. mansoni in deprived mice. Sera from mice immunized with other S. mansoni egg fractions, and which did not contain antibodies reactive with ω 1, were not hepatoprotective. Antigen ω 1 is compared and contrasted with other S. mansoni egg antigens that have been described.

Schistosoma Mansoni Infections in T-Cell Deprived Mice, and the Ameliorating Effect of Administering Homologous Chronic Infection Serum

Liver changes occurring in mice deprived of their T-cells by a combination of thymectomy and anti-mouse thymocyte serum, and in immunologically intact control mice, were followed during the early stages of heavy Schistosoma mansoni infections. Lesions in both groups began developing by day 38 and were maximal by day 48. Hepatic changes in control mice culminated in large hypersensitivity granulomas, tissue eosinophilia, portal periphlebitis, fibrosis, vascular obstruction, and infarction leading to arterialization and preferential sinusoidal channeling. Deprived mice showed greatly reduced egg reactions composed principally of macrophages, monocytes, and occasional neutrophils, and only minimal alteration of liver architecture; however, focal and disseminated hepatocellular lesions became prominent as the infections progressed, and by day 48 virtually every hepatocyte was affected. Typically, hepatocytes showed microvesicular cytoplasmic damage (steatosis) or ballooning degeneration with accompanying nuclear pyknosis or karyorrhexis. This cellular pathology may be attributed to the direct or indirect effect of eggs or egg products on liver cells. The administration of chronic infection serum obtained from immunocompetent mice to T-cell deprived mice dramatically eliminated the hepatocellular lesions. It also increased eosinophil participation and fibrosis in the egg reactions but did not restore the size and other cellular features typical of egg hypersensitivity granulomas. Serum from uninfected normal mice was found to lack these effects.

Schistosoma Mansoni Infections in T-cell Deprived Mice, and the Ameliorating Effect of administering Homologous Chronic Infection Serum

Liver changes occurring in mice deprived of their T-cells by a combination of thymectomy and anti-mouse thymocyte serum, and in immunologically intact control mice, were followed during the early stages of heavy Schistosoma mansoni infections. Lesions in both groups began developing by day 38 and were maximal by day 48. Hepatic changes in control mice culminated in large hypersensitivity granulomas, tissue eosinophilia, portal periphlebitis, fibrosis, vascular obstruction, and infarction leading to arterialization and preferential sinusoidal channeling. Deprived mice showed greatly reduced egg reactions composed principally of macrophages, monocytes, and occasional neutrophils, and only minimal alteration of liver architecture; however, focal and disseminated hepatocellular lesions became prominent as the infections progressed, and by day 48 virtually every hepatocyte was affected. Typically, hepatocytes showed microvesicular cytoplasmic damage (steatosis) or ballooning degeneration with accompanying nuclear pyknosis or karyorrhexis. This cellular pathology may be attributed to the direct or indirect effect of eggs or egg products on liver cells. The administration of chronic infection serum obtained from immunocompetent mice to T-cell deprived mice dramatically eliminated the hepatocellular lesions. It also increased eosinophil participation and fibrosis in the egg reactions but did not restore the size and other cellular features typical of egg hypersensitivity granulomas. Serum from uninfected normal mice was found to lack these effects.

Relationship between tumour growth rate and proteic variations in interstitial subcutaneous fluid and serum: Possible thymic control

Some murine tumours stimulate the proliferation of target cells in diffusion chambers implanted subcutaneously near the tumour. The growth of tumours with or without the property to stimulate the proliferation of target cells was studied in relation to the proteic variations in interstitial subcutaneous fluid and serum in normal hosts and thymectomized or thymus-deprived hosts. “Stimulating” tumours were found to exhibit a much faster growth than “non stimulating” tumours, in normal hosts. A significant protein decrease was observed in interstitial fluid of mice bearing “stimulating” tumours as compared to control mice. In contrast, the analysis of interstitial fluid and serum of mice bearing “non stimulating” tumours revealed a significant proteic increase. The study of the growth behaviour of these tumours in T-cell deprived mice revealed a deceleration of the “stimulating” tumours, and a heavy acceleration for the “non stimulating” tumours. No proteic variation as compared to control mice was found in interstitial fluid and serum of tumour bearing T-cell deprived mice. The hypothesis was formulated that some relationship exists between tumour growth rate and proteic variations in interstitial subcutaneous fluid and serum which might be under thymic control.

T-cell activation in murine malaria.

THE immune response of rodents to malaria is thymus dependent. Plasmodium berghei infections are more severe in neonatally thymectomised rats than in intact controls1, whereas P. yoelii (P. berghei yoelii) infections which are self-resolving in normal CBA mice prove fatal in T-cell deprived CBA mice (Jayawardena et al., unpublished) or congenitally athymic nude mice2. Malarial infections are also known to depress immune responses to certain antigens. In the mouse, they reduce the antibody3 and splenic plaque forming cell4 response to sheep red blood cells (SRBCs), render animals more susceptible to lymphomagenic viruses5, and severe long term infections prolong xenogeneic skin graft survival time6. It has been suggested that such impaired immune reactivity reflects defective lymphocyte or macrophage function, but there has been no unequivocal evidence in support of these possibilities.

Effect of local injection of Corynebacterium parvum on the growth of a murine fibrosarcoma.

Local injection (i.e. injection at the site of tumour inoculation) of strains of C. Parvum which have a significant anti-tumour effect when given systemically (i.e. intravenously or, in the case of subcutaneous tumour transplant, intraperitoneally) strongly inhibits the growth of isogeneic transplants of a fibrosarcoma in intact CBA mice but has little or no effect on subcutaneous transplants of the same tumour in T-cell deprived mice. The anti-tumour effect of local injection of C. parvum, unlike that of systemic injection in this particular tumour system, thus appears to be T-cell dependent.

The effect of cell dose and distribution on the development of a transplanted tumour

Experiments with an isogeneically-transplanted murine sarcoma which has a TD 50 of about 30 cells have shown inter alia that for a given total cell dose the proportion of mice which develop tumours is not altered by distributing the dose among 10 sites as against concentrating it in a single site, whereas the tumour volume per mouse 24 days after inoculation may be markedly reduced. At doses of 100 cells per site or more the chance of take at a site is not influenced by the presence of other sites, but the mean rate of growth at a site is reduced in the presence of other sites. In T-cell deprived mice single site inoculation of 1000 cells results in slower growth than in intact mice, but distribution of the dose among multiple sites in deprived mice does does not further reduce the total tumour volume (measured 18 or 24 days after inoculation). In the light of these and other findings it is postulated that, following tumour inoculation, there is an early local host reaction probably mediated by macrophages, which causes rapid destruction of some of the transplanted cells, the number destroyed depending partly on the intensity of the reaction and partly on a mutually protective effect of the tumour cells. With tumours which possess tumour-specific transplantation antigens there is in addition a slower immunological reaction which may destroy some or all of the cells which have survived the early reaction. A modification of the hypothesis put foreward previously to account for the slower growth of the tumour in T-cell deficient mice is proposed.

The growth of tumours in T-cell deprived mice and their response to treatment with Corynebacterium parvum.

Severe depletion of thymus-derived lymphocytes does not reduce, and may significantly increase, the resistance of mice to syngeneic tumours, although it grossly impairs their ability to reject allotransplants. Injection of killedC. parvumcauses further inhibition of tumour growth in T-cell deprived mice to an extent comparable to that resulting from the same dose ofC.parvumin normal mice. This appears to lend support to the hypothesis that the antitumour effect ofC. parvumdepends primarily on macrophage stimulation.