Toxoplasma gondii infection inhibits the development of lupus-like syndrome in autoimmune (New Zealand Black x New Zealand White) F1 mice

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of autoantibodies and lupus nephritis. In the present study using New Zealand Black (NZB) x New Zealand White (NZW) F1 (NZBW F1) mice, we planned to investigate the effects of Toxoplasma gondii infection on the progress of lupus nephritis. Female NZBW F1 mice at the age of 2 months were perorally infected with T. gondii. The T. gondii infection reduced the number of mice developing proteinuria and immune complex deposits in their kidneys and prolonged their life span. A marked decrease in the levels of IgM and IgG anti-DNA antibodies, especially IgG2a and IgG3 subclasses, was observed in T. gondii-infected NZBW F1 mice at 9 months of age. The level of anti-HSP70 IgG autoantibody in the sera of NZBW F1 mice was significantly higher than that in control mice at 9 weeks after T. gondii infection. Moreover, NZBW F1 mice treated with anti-self heat shock protein 70 (HSP70) monoclonal antibody were substantially protected against the onset of glomerulonephritis. Further, down-regulation of intracellular expression of IFN-gamma and IL-10 was shown in spleen cells of T. gondii-infected NZBW F1 mice. This was consistent with the previous data indicating the involvement of Th1-type and Th2-type cytokines in the development of lupus-like nephritis. These results suggest that T. gondii infection is capable of preventing the development of autoimmune renal disorder in NZBW F1 mice.     

Immunoglobulin and complement deposits in the lungs of New Zealand Black/White mice

Summary Forty-four New Zealand Black/White (NZB/W) F1 hybrid mice were studied for evidence of immune complex deposition in the lungs and kidneys. Positive immunofluorescence was seen in the lungs of 27 mice. The pattern of lung fluorescence was granular in association with capillary walls in 16 mice and intracellular in 12. The incidence of granular fluorescence was increased with age and was seen in 80% of the lungs of mice over 13 months old.There was a correlation between capillary wall fluorescence in the lungs and the kidneys (P<0.001) and between lung cellular fluorescence and renal mesangial fluorescence (P<0.001). The role of immune complex deposition in human pulmonary disease is discussed.     

The role of low affinity antibody in immune complex disease. The quantity of anti-DNA antibodies in NZB/W F1 hybrid mice.

The level and avidity of anti-DNA antibody in the serum of New Zealand Black/White (NZB/W F1) hybrid mice has been determined. The results show that there is an age and sex-related variation in the avidity of this antibody. In mice of both sexes, the avidity of circulating anti-DNA antibody increases up to 5 months of age; thereafter the avidity falls with increasing age. These variations are more marked in males, but female mice consistently have lower avidity anti-DNA antibody than males. Thus the time of onset, time course and severity of the murine lupus syndrome in NZB/W F1 mice are associated with the presence of increasing levels of low avidity anti-DNA antibody in the serum. These results are discussed in the context of the possible role of low avidity antibody in immune complex disease.     

Thymic function in NZB mice. I. Duration of thymic function in New Zealand Black (NZB) mice

Ageing 6–9-month-old NZB mice have been grafted with a syngeneic new-born thymus. Rapid normalization of the initially low level of circulating thymic factor (TF) and of responsiveness of spleen cells to phytohaemagglutinin (PHA) and concanavalin A (con A) was observed. However, this restoration was transient, both serum TF and mitogen responsiveness returning to the initially low levels within a month. These data support the idea that NZB mice present an early depression of thymus endocrine function, independent of anti-thymus antibodies and that recovery of mitogen responsiveness may be transient, directly dependent on serum TF level.     

Reduction of graft-versus-host disease in neonatal F1 hybrid mice.

Pre-immunization of BALB/c (H-2d) mothers with C57BL/10 (H-2b) or CBA/H (H-2k) spleen cells partially protected the F1 hybrid offspring of (BALB/c x C57BL/10) or (BALB/c x CBA/H) matings from graft-versus-host-disease (GVHD) induced by neonatal intraperitoneal inoculation with spleen cells of the paternal strain. The effects achieved were manifest as a reduction in mortality. Experiments to establish whether the phenomenon was antibody mediated were performed by passive pre-immunization of BALB/c mothers with alloantisera obtained from BALB/c previously immunized with C57BL/10 spleen cells. Alloantisera produced an equivalent reduction in GVHD mortality. Some of the F1 mice that survived challenge with paternal strain spleen cells were proven to be haemopoietic chimaeras using immunofluorescence with anti-MHC monoclonal antibodies and polymorphism of the enzyme glucose-phosphate-isomerase present in the strains used. The possible mechanisms of protection from GVHD in our mouse model are discussed.     

The paradoxical effects of diethyldithiocarbamate: comparisons between New Zealand black/white F1 hybrid and Balb/c mice

Diethyldithiocarbamate (DTC), an immunomodulative agent suggested to enhance T cells, has been shown to prolong life in autoimmune MRL-lpr/lpr mice. In addition to increased survival, MRL-lpr/lpr mice treated with DTC displayed a number of changes in expression of cell surface antigens as well as decreased serum autoantibody levels. To determine if DTC treatment would have similar positive effects on another murine model of autoimmune disease, we studied the New Zealand Black/White F1 hybrid (NZB/W). In addition, the effects of DTC treatment on cell surface antigen expression were compared between the NZB/W and a normal murine strain, the Balb/c. DTC treatment increased the density of cell surface antigens in the NZB/W, but decreased the density of these antigens in the Balb/c. Treatment with DTC induced distinct changes in the percentage of cells expressing specific surface antigens that differed between the NZB/W and the Balb/c. There was no affect on serum anti-DNA and anti-histone antibody levels or on survival in NZB/W mice treated with DTC. Therefore, while DTC treatment did not successfully influence the disease course in the NZB/W, it did result in specific changes in cell surface antigens. These data demonstrate that DTC is capable of inducing a variety of immunologic changes depending upon the strain treated.     

Genetic control of the immune response to ferritin in F1 hybrid mice.

The immune response to the antigen horse spleen ferritin, has been investigated in ten inbred parental strains and seven different F1 hybrid strains of mice, using an antigen excess technique. The degree of dominance in an F1 hybrid system can be estimated by using the Fisher dominance index. The responses in F1 hybrid animals, obtained from crosses of high and low responder parents, varied from dominant to recessive but the overall mean dominance index for the ferritin immunogenetic system was found to be -0.0467 +/- 0.0083 (mean +/- s.e.), a value close to zero, which suggests a codominant mode of inheritance of IR-genes to ferritin and this is consistent with most published data in other F1 IR-gene systems.     

Suppression of autoimmune disease in New Zealand mice associated with infection with malaria. I. (NZB × NZW) F1 hybrid mice

Female (NZB × NZW) F₁ hybrid (B/W) mice were infected with Plasmodium berghei at the age of 1 month. In contrast to the high mortality from renal disease observed in control female mice of this strain, all of the malaria-infected female mice were alive at 12 months of age and none had any clinical features of severe renal disease. This finding gives some support to the hypothesis that a background of repeated parasitic infection may modify the development of autoimmune disease in man.     

Autoimmunity and tumor resistance. 3-Methylcholanthrene tumorigenesis in New Zealand Black mice.

Skin tumors induced by the subcutaneous injection of 3-methylcholanthrene (3-MC) in New Zealand Black (NZB) mice had a delayed development and lower frequency compared with BALB/c and C57BL mice. In the SJL/J strain, the incidence of tumors was lower than in the NZB, but with the same delayed development. Most of the tumors in the BALB/c, C57BL, and SJL/J strains were sarcomas; more than one third of the tumors in the NZB mice were squamous cell carcinomas. The greatest frequency and most rapid development of tumors in the NZB, as a function of age at the time of injection of 3-MC, occurred at 4 months. Young (3.5 and 7 weeks) and 12-month-old tumor incidence in the 4-month-old NZB was decreased by treatment with antithymocyte serum (ATS). Five hundred rad whole-body x-irradiation accelerated the onset of tumors but did not increase the final incidence. 3-MC injection and the presence of skin tumors had no influence on the development of glomerulonephritis or hematopoietic neoplasms in the NZB mice. Coombs' positive anemia was not influenced by 3-MC injection, but there was an earlier and increased incidence of positive Coombs' tests in tumor-bearing animals. Liver aryl hydrocarbon hydroxylase (AHH) specific activity was low in the young NZB, increased gradually with age, and was higher in the female mice.     

Accelerated autoimmune disease and lymphoreticular neoplasms in F1 hybrid PN/NZB and NZB/PN mice

This report describes the first studies of inheritance of autoimmunity in inbred Palmerston North (PN) mice, a model of systemic lupus erythematosus (SLE). Mating of PN mice with the nonautoimmune DBA/2 strain produced evidence that PN disease had a recessive mode of inheritance. When PN mice were crossed with autoimmune NZB mice, female offspring from both crosses developed anti-DNA antibodies and died prematurely with vasculitis, renal disease, and lymphomas. In contrast, reciprocal hybrid males had different patterns of mortality; PN/NZB males from the PN female X NZB male mating had moderately prolonged life spans, whereas NZB/PN males from the opposite cross (NZB female X PN male) had prolonged survival to the mean age of 104 weeks. To determine if testicular hormones were solely responsible for increased longevity in hybrid males, PN/NZB and NZB/PN mice were castrated at 2 weeks of age and compared to sham-operated littermate controls. Prepubertal castration did not influence longevity in PN/NZB males, but loss of gonadal hormones significantly reduced life spans in reciprocal NZB/PN males. Female hybrids were not affected by oophorectomy. Because castration changed disease expression only in male hybrids from the NZB female X PN male cross, it was concluded that parentage influenced sensitivity to the protective effects of male hormones. Although surgical sterilization had disparate effects on males, castrated PN/NZB and NZB/PN males consistently outlived oophorectomized females. The lack of clear-cut reversal of disease in males subjected to early castration suggested that nonhormonal, possibly genetic, factors contributed to longevity in both groups of male hybrids.     

Abnormalities of third-order suppressor T cells in old (New Zealand black x New Zealand white) F1 mice.

The suppressor T cell (Ts) function of old NZW, NZB, C57BL/6 and (NZB X NZW) F1 [B/W)F1), mice to the 2,4-dinitro-1-fluorobenzene (DNFB) hapten was studied. Intravenous administration of dinitrophenyl (DNP) coupled syngeneic lymphoid cells (which normally induce DNP specific suppression) did not result in suppression of DNFB-specific contact hypersensitivity (CS) responses in old NZB or (B/W) F1 mice. Nevertheless, when spleen cells from these old mice were injected into young mice (either (B/W)F1 or A/Sn), strong suppression of the induction phase of CS responses was observed. In addition, effector phase suppressor activity was also observed when splenic cells from tolerized old (B/W) F1 donors were transferred into young (B/W)F1 mice during the effector phase of the CS response. In both cases, the significant cells in the transfer were I-J+ T cells. Thus, the old mice retained functional Ts1 and Ts2 suppressor cells. However, the suppressive activity of the old mice could be reconstituted with spleen cells from primed young mice, suggesting that they have a defect in the Ts3 subset. This was further supported by the finding that the significant cells from the primed young mice were I-J positive and cyclophosphamide-sensitive.     

Particles resembling murine leukaemia virus in New Zealand Black mice

Particles which morphologically resembled murine leukaemia virus were detected by electron microscopy in the tissues (spleen, thymus, inguinal lymph nodes, bone marrow or pancreas) but not in serum or plasma pellets of untreated conventional New Zealand Black (NZB) mice aged 1–82 weeks. They were also found in the corresponding tissues of NZB mice which had been thymectomized shortly after birth. The presence of similar particles in the spleen, thymus or pancreas of conventional NZB embryos and, additionally, in the lymph nodes of NZB mice which had originally been introduced into a germ-free environment by Caesarian section and fostering on germ-free mice of another strain, suggests that the virus is transmitted `vertically' through the germ cells or placenta. Preliminary investigations showed similar particles in the organs of conventional F₁ (NZB × NZW) hybrid and New Zealand White (NZW) mice.

Large numbers of particles also resembling murine leukaemia virus were found in the spleen and in plasma or serum pellets of young conventional NZB mice which had developed reticulum cell neoplasia following serial passage of lymphoid cell suspensions from ageing conventional NZB donors.

The possible relationship of these particles to the autoimmune reactions and malignant changes which occur spontaneously in conventional NZB mice is discussed.

     

Pristane induced arthritis. II. Genetic regulation in F1 hybrid mice and cellular immune abnormalities following pristane injection

Pristane-induced arthritis was investigated in DBA/1, DBA/2, and BALB/c mice, and F1 hybrid mice generated from inter-crosses between these strains. The incidence of disease in F1 hybrid mice was significantly lower than the susceptible parental strains (DBA/1 and BALB/c), and resistance to arthritis was observed in both DBA/2 mice and the (DBA/2 x BALB/c) F1 hybrid mice. Several cellular immune abnormalities were observed in pristane-injected DBA/1 mice. Con A mitogen responses were depressed following pristane injection, and a functional suppressor cell population was detected. Delayed type hypersensitivity responses to type II collagen were observed in pristane injected mice. The intraperitoneal injection of pristane appears to alter immune regulation and induce autoimmune responses to connective tissue components.     

The immune response in NZB × NZW F1 hybrid mice

A study was made of the immune response of NZB × NZW F₁ hybrid (BW) mice against `H' antigen of Salmonella, sheep red blood cells, bovine serum albumin and allogeneic tumour cells. The responses of old BW mice having autoimmune glomerulonephritis were compared with those of young healthy mice. It was found that the mice develop immune depression concurrently with the autoimmune process. In old BW mice, the immune response is of the same type as the response observed in neonatally thymectomized mice. Neither age alone, nor functional deficiency of the thymus could account for this immune depression. It is suggested that the ability to respond to foreign antigens was probably depressed by the competition provided by autoantigens.     

The clearance and localization of nucleic acids by New Zealand and normal mice

The clearance and localization of native DNA, denatured DNA, and double-stranded synthetic RNA was studied in New Zealand Black/White hybrid mice, which develop an illness closely resembling human systemic lupus erythematosus, and in normal mice. The three nucleic acids were rapidly cleared from the circulation in all strains studied. Serum nucleases did not account for this rapid clearance, indicating that the nucleic acids were taken up as macromolecules. The polymers were concentrated in the liver and spleen, suggesting uptake by the reticulo-endothelial system. Animals with circulating antibody cleared the nucleic acids even more rapidly. New Zealand mice did not differ from normal mice in their metabolism of nucleic acids.     

Increased survival times of New Zealand hybrid mice immunosuppressed by graft-versus-host reactions.

New Zealand mice develop autoimmune disease usually accompanied by glomerulonephritis. A graft-versus-host reaction was induced in New Zealand Black X New Zealand White F1 hybrid mice by administration of New Zealand White spleen cells. The mice so treated had diminished antibody responses to both an exogenous antigen (sheep red blood cells) and an endogenous antigen (native DNA). They had much less glomerulonephritis and increased survival times compared to unmanipulated controls, apparently due to immunosuppression. Similar hybrid mice treated with high doses of cyclophosphamide (70mg/kg/week) were more immunosuppressed than mice with graft-versus-host reactions and had even greater survival times.