Mercury induces polyclonal B cell activation,autoantibody production and renal immune complex deposits in young (NZB × NZW)F1 hybrids

It is well established that in susceptible mouse strains, chronic treatment with subtoxic doses of mercuric chloride (HgCl₂) induces a systemic autoimmune disease, which is characterized by increased serum levels of IgG1 and IgE antibodies, by the production of anti-nucleolar antibodies and by the development of immune complex-mediated glomerulonephritis. Susceptibility to mercury is partly under the control of major histocompatibility complex genes. To study the susceptibility to mercury further, we investigated the in vivo effects of mercury in young autoimmune disease prone (NZB × NZW)F1 (H-2^d/z) mice prior to establishment of spontaneous autoimmune disease. Mercury-susceptible SJL (H-2^s) mice and mercury low-responder BALB/c (H-2^d) mice were used as positive and negative controls, respectively. In (NZB × NZW)F1 mice, treatment with mercury stimulated an intense antibody formation characterized by increased numbers of splenic IgG1 and IgG3 antibody-producing cells as well as by elevated serum IgE levels. Injection with mercury also induced an increased production of IgG1, IgG2b and IgE antibodies in SJL, but not in BALB/c mice. The mercury-induced IgG1 response in (NZB × NZW)F1 and SJL mice was found to be polyclonal and autoantibodies against double-stranded (ds)DNA, IgG, collagen, cardiolipin, phosphatidylethanolamine as well as antibodies against the hapten trinitrophenol were produced. In addition, SJL, but not (NZB × NZW)F1 or BALB/c mice, produced IgG1 anti-nucleolar antibodies after treatment with mercury. Further studies demonstrated that (NZB × NZW)F1 and SJL mice developed high titers of renal mesangial immune complex deposits containing IgG1 antibodies 3 weeks after injection with mercury. Thus, a mouse strain genetically prone to develop spontaneous autoimmune diseases is highly susceptible to mercury-induced immunopathological alterations.     

Molecular and Idiotypic Analyses of the Antibody Response to Cryptococcus neoformans Glucuronoxylomannan-Protein Conjugate Vaccine in Autoimmune and Nonautoimmune Mice

The antibody response to Cryptococcus neoformans capsular glucuronoxylomannan (GXM) in BALB/c mice frequently expresses the 2H1 idiotype (Id) and is restricted in variable gene usage. This study examined the immunogenicity of GXM-protein conjugates, V (variable)-region usage, and 2H1 Id expression in seven mouse strains: BALB/c, C57BL/6, A/J, C3H, NZB, NZW, and (NZB x NZW)F(1) (NZB/W). All mouse strains responded to vaccination with GXM conjugated to tetanus toxoid (TT), the relative magnitude of the antibody response being BALB/c approximately C3H > C57BL/6 approximately NZB approximately NZW approximately NZB/W > A/J. Analysis of serum antibody responses to GXM with polyclonal and monoclonal antibodies to the 2H1 Id revealed significant inter- and intrastrain differences in idiotype expression. Thirteen monoclonal antibodies (MAbs) (two immunoglobulin M [IgM], three IgG3, one IgG1, three IgG2a, two IgG2b, and two IgA) to GXM were generated from one NZB/W mouse and one C3H/He mouse. The MAbs from the NZB/W mouse were all 2H1 Id positive (Id(+)) and structurally similar to those previously generated in BALB/c mice, including the usage of a V(H) from the 7183 family and Vkappa5.1. Administration of both 2H1 Id(+) and Id(-) MAbs from NZB/W and C3H/H3 mice prolonged survival in a mouse model of cryptococcosis. Our results demonstrate (i) that V-region restriction as indicated by the 2H1 Id is a feature of both primary and secondary responses of several mouse strains; and (ii) that there is conservation of V-region usage and length of the third complementarity-determining region in antibodies from three mouse strains. The results suggest that V-region restriction is a result of antibody structural requirements necessary for binding an immunodominant antigen in GXM.     

Differences in the occurrence of hypertension among (NZB X NZW)F1, MRL-lpr, and BXSB mice with lupus nephritis.

Lupus-prone (NZB X NZW)F1 (B X W) mice and MRL-lpr and BXSB mice were examined for the prevalence of hypertension and levels of plasma renin activity (PRA). Hypertension (greater than 145 mmHg) was observed only in female and male B X W mice with severe nephritis; in female MRL-lpr and male BXSB mice severe nephritis developed without blood pressure elevation (80-135 mmHg). The B X W parental strains, NZB and NZW, and the MRL-lpr congenic partners, MRL- +, did not become hypertensive as they aged. Other strains of mice, aged 3-32 months (A/HeN, BALB/cJ, BALB/cByJ, B10.S/Sg, B10.D2/ oSn , CBA/J, C3H/HeJ, SJL/J and [SJL X NZW]F1), also had normal blood pressure (98-122 mmHg). All mice with lupus nephritis had low PRA, even those with hypertension; furthermore, the MRL-lpr strain had low or undetectable PRA (2 +/- 1 ng/ml/hr), even when kidneys were normal. NZB, NZW, and MRL- + mice had normal PRA (10-16 ng/ml/hr). Thus, B X W mice frequently developed low renin hypertension during the last phase of their renal disease; whereas MRL-lpr and BXSB mice died from renal disease without observable increases in blood pressure.     

Identification of an epitope on the recombinant bovine PrP that is able to elicit a prominent immune response in wild-type mice

The main cause for the development of transmissible spongiform encephalopathies (TSE) is the conformational change of prion protein from the normal cellular isoform (PrP(C)) into the abnormal isoform, named prion (PrP(Sc)). The two isoforms have the same primary structure, and with PrP being highly conserved among different species, no immune response to PrP(Sc) has been observed in infected humans or other mammals so far. The problem of inducing immune response was encountered when producing monoclonal antibodies against PrP, therefore mice lacking a functional Prnp gene were predominantly used for the immunization. In the present paper we report that by immunizing wild-type BALB/c mice with chemically unmodified recombinant bovine PrP a potent humoral immune response was achieved. Furthermore, we were able to isolate the monoclonal antibody (mAb) E12/2 and few other mAbs, all reacting specifically with bovine and human PrP, but not with PrP from several other mammals. The epitope of mAb E12/2 is located at the C-terminal end of helix 1, with His155 being crucial for binding. It has been proven that mAb E12/2 is useful for human and bovine TSE research as well as for diagnostics. Our results show that there are sufficient structural differences between mouse and bovine PrP to provoke a prominent humoral immune response.     

Guanidine hydrochloride extraction and detection of prion proteins in mouse and hamster prion diseases by ELISA

Current detection of transmissible spongiform encephalopathy (TSE) relies on the proteolytic generation of a protease-resistant core from the scrapie isoform of prion protein (PrP(Sc)) followed by immunoblotting. This process is non-quantitative, time-consuming, and technically demanding. Recently, an alternative in vitro test for TSE based on the differential extraction of brain homogenates using guanidine hydrochloride followed by DELFIA (Dissociation Enhanced Lanthanide FluoroImmunoAssay) has been developed. In the present study, this approach was adopted using a panel of anti-PrP monoclonal antibodies (MAbs) in conventional sandwich enzyme-linked immunosorbent assay (ELISA) to investigate hamster and two distinct strains of mouse prion diseases. Although PrP species were present in both soluble and insoluble fractions from normal as well as TSE samples, only the PrP species in the insoluble fractions from the latter samples were protease-resistant. In addition, certain anti-PrP MAb pairs could distinguish the PrP species in infected brains from those in the normal samples. The ability to differentiate disease-associated PrP isoforms without proteinase K digestion could serve as a panacea for developing a reliable and rapid diagnostic test for prion diseases.     

Genetic association between natural autoantibody responses to histones and DNA in murine lupus.

Genetic regulation of the spontaneous anti-histone antibody production in systemic lupus erythematosus (SLE) was studied using the H-2-congenic and T cell receptor beta chain gene complex (TCR beta)-congenic NZB and NZW strains and their crosses. We found that the original, parental H-2d/d NZB mice produced significantly higher titers of serum IgM class anti-histone antibodies than did the congenic H-2d/z or H-2z/z NZB mice. However, none of these three NZB strains produced IgG antibodies. The NZW strain of any H-2 haplotype did not produce IgM and IgG anti-histone antibodies. The IgG anti-histone antibodies were produced only by H-2d/z heterozygous NZB x NZW F1, but not by homozygous H-2z/z or H-2d/d NZB x NZW F1 mice. In studies using (NZB x NZW) F1 x NZB backcross mice, only the progeny having both H-2d/z and NZW-type TCR beta genotypes produced high amounts of IgG antibodies. There was a tight linkage between the NZW-type TCR beta and the production of IgG anti-histone antibodies in TCR beta-congenic NZB x NZW F1 mice. All these findings were in keeping with our preceding observations on the genetic regulation of anti-DNA antibodies in these mice and suggest that certain common mechanisms such as super-antigen-mediated or common idiotope-mediated regulations may underlie the production of these two distinct autoantibodies in NZB x NZW F1 mice.     

Disease-associated prion protein is not detectable in human systemic amyloid deposits

Cerebral and cardiac amyloid deposits have been reported after scrapie infection in transgenic mice expressing variant prion protein (PrP(C)) lacking the glycophosphatidylinositol anchor. The amyloid fibril protein in the systemic amyloid deposits was not characterized, and there is no clinical or pathological association between prion diseases and systemic amyloidosis in humans. Nevertheless, in view of the potential clinical significance of these murine observations, we tested both human amyloidotic tissues and isolated amyloid fibrils for the presence of PrP(Sc), the prion protein conformation associated with transmissible spongiform encephalopathy (TSE). We also sequenced the complete prion protein gene, PRNP, in amyloidosis patients. No specific immunohistochemical staining for PrP(Sc) was obtained in the amyloidotic cardiac and other visceral tissues of patients with different types of systemic amyloidosis. No protease-resistant prion protein, PrP(res), was detectable by Western blotting of amyloid fibrils isolated from cardiac and other systemic amyloid deposits. Only the complete normal wild-type PRNP gene sequence was identified, including the usual distribution of codon 129 polymorphisms. These reassuringly negative results do not support the idea that there is any relationship of prions or TSE with human systemic amyloidosis, including cardiac amyloid deposition.     

CpG oligodeoxynucleotide-enhanced humoral immune response and production of antibodies to prion protein PrPSc in mice immunized with 139A scrapie-associated fibrils

Prion diseases are characterized by conversion of the cellular prion protein (PrP(C)) to a protease-resistant conformer, the srapie form of PrP (PrP(Sc)). Humoral immune responses to nondenatured forms of PrP(Sc) have never been fully characterized. We investigated whether production of antibodies to PrP(Sc) could occur in PrP null (Prnp(-/-)) mice and further, whether innate immune stimulation with the TLR9 agonist CpG oligodeoxynucleotide (ODN) 1826 could enhance this process. Whether such stimulation could raise anti-PrP(Sc) antibody levels in wild-type (Prnp(+/+)) mice was also investigated. Prnp(-/-) and Prnp(+/+) mice were immunized with nondenatured 139A scrapie-associated fibrils (SAF), with or without ODN 1826, and were tested for titers of PrP-specific antibodies. In Prnp(-/-) mice, inclusion of ODN 1826 in the immunization regime increased anti-PrP titers more than 13-fold after two immunizations and induced, among others, antibodies to an N-terminal epitope, which were only present in the immune repertoire of mice receiving ODN 1826. mAb 6D11, derived from such a mouse, reacts with the N-terminal epitope QWNK in native and denatured forms of PrP(Sc) and recombinant PrP and exhibits a K(d) in the 10(-)(11) M range. In Prnp(+/+) mice, ODN 1826 increased anti-PrP levels as much as 84% after a single immunization. Thus, ODN 1826 potentiates adaptive immune responses to PrP(Sc) in 139A SAF-immunized mice. These results represent the first characterization of humoral immune responses to nondenatured, infectious PrP(Sc) and suggest methods for optimizing the generation of mAbs to PrP(Sc), many of which could be used for diagnosis and treatment of prion diseases.     

Comparison of T cell-mediated immune responsiveness of NZB, (NZB x &NZW)F1 hybrid and other murine strains.

The age-dependent capacity of NZB and (NZB x NZW)F1 hybrid, BALB/c, DBA/2, C57BL/6 and C3H mice to generate T cell-mediated immune responses was assessed qualitatively and quantitatively by measuring the following effector functions: (a) the time course of alloreactive cytotoxic T-cell activity triggered in vitro was comparable for NZ and other mouse strains; cell reactivity generated in vivo against EL4 tumour cells was low in young (NZB x NZW)F1 mice and in DBA/2 mice but was comparable for older (NZB x NZW)F1, NZB and other mouse strains; (b) the time-dependent, vaccinia virus-specific, cytotoxic T-cell activity after systemic infection was similar for all mouse strains; (c) the T cell-dependent primary footpad swelling after local injection with lymphocytic choriomeningitis virus was within the same range for all mouse strains tested with respect to size and kinetics of the reaction; (d) the cell-mediated immune protection against Listeria monocytogenes after systemic infection revealed that NZ mice are, independent of age, more susceptible than C3H or C57BL/6 mice and comparable to A strain mice. Therefore, these responses in young, or clinically relatively normal older, NZB or (NZB x NZW)F1 strains that are affected by a lupus-like autoimmune disease did not differ markedly from the range of responses of other mouse strains of 2-14 months of age, which are not known to be similarly diseased. Thus, overall cell-mediated immunity of NZ mice as assessed quantitatively and kinetically in these functional models is within normal ranges. Possible T-cell defects may therefore be selective and either do not occur or were not detected in these models.     

The Effect of Cytokines on the Activation-Induced Apoptosis of B Cells in Autoimmune NZB X NZW F1 Mice

Programmed cell death (apoptosis) is an essential process in the development of various tissues and its involvement has been proposed for the elimination of self-reactive immature T and B lymphocytes when self antigens are first encountered. In order to further investigate the role of apoptosis in the pathogenesis of autoimmune disease, the apoptosis of lipopolysaccharide (LPS)-activated B cells, peritoneal cells from NZB x NZW F1 (NZB/W F1) mice and nonautoimmune BALB/c mice were assayed using an in vitro culture system. Splenic B cells were isolated and then stimulated with LPS before further activated with crosslinking antimu antibody. In addition, the apoptosis of peritoneal cells induced by crosslinking antimu antibody was also analyzed. The data revealed that the specific apoptosis of both activated B cells and peritoneal cells induced by crosslinking antimu antibody was very similar comparing NZB/W F1 and nonautoimmune BALB/c mice. This activation-induced B-cells apoptosis could be rescued, however, with the addition of cytokines such as interleukin (IL)-5 or IL-10, to the culture. The results suggest that there is no endogenous defect in the apoptosis of activated B cells for autoimmune NZB/W F1 comparing nonautoimmune BALB/c mice. Notably, however, abnormally high levels of the type 2 T helper (Th2)-related cytokines such as IL-5 or IL-10 may play an important role in the abnormal expansion of activated B cells in autoimmune NZB/W F1 mice.     

Loss of lymphocyte chalone activity in mice with autoimmune disease.

Lymphocyte chalone from the spleens of old BALB/c, young BALB/c and young NZB mice caused significant suppression of the proliferative response of BALB/c and NZB spleen cells to T and B mitogens, whereas lymphocyte chalone from old NZB spleen did not suppress. Lymphocyte chalone from young and old NZB mice was tested using different ages of NZB/NZW responding spleen cells; at all ages concanavalin A- and lipopolysaccharide-induced proliferation was suppressed less by the chalone from old NZB mice than from that of young NZB mice. The responding NZB/NZW cells were suppressed equivalently at all ages studied. The basis for the loss of lymphocyte chalone activity in old NZB mice remains unknown; however, it appears likely that this event has a role in the disturbance of the negative feedback control system which contributes to NZB autoimmune disease.     

Contribution of the gene linked to the T cell receptor beta chain gene complex of NZW mice to the autoimmunity of (NZB x NZW)F1 mice.

We have investigated the contribution to the autoimmune disease of (NZB x NZW)F1 (NZB/W) mice made by the T cell receptor beta (TcR beta) chain gene complex, or genes linked to it, that are derived from the NZW strain. For this we developed the NZW.TcR beta NZB strain, a NZW congenic line carrying the TcR beta of NZB type, and produced NZB x NZW.TcR beta NZB (NZB/W.TcR beta NZB)F1 mice. We compared the amounts of anti-DNA and anti-histone antibodies and also the severity of lupus nephritis in these mice with those in the original NZB/W F1 mice. We obtained evidence for significantly lower serum levels of autoantibodies to double-stranded and single-stranded DNA and histone, and a later onset and a lower incidence of proteinuria in the NZB/W.TcR beta NZB F1 mice than in the original NZB/W F1 mice. These findings clearly indicate that the gene(s) within or closely linked to the TcR beta chain gene complex on chromosome 6 of the NZW strain acts to intensify the feature of systemic lupus erythematosus in the NZB/W F1 strain. The significant relationship of this finding to the strict dependency of NZB/W F1 disease on the H-2d/H-2z heterozygosity is discussed.     

Interferon-α induces unabated production of short-lived plasma cells in pre-autoimmune lupus-prone (NZB×NZW)F1 mice but not in BALB/c mice

IFN-α is known to play a critical role in the pathogenesis of systemic lupus erythematosus (SLE), but the mechanisms remain unclear. We previously showed that within weeks, exposure to IFN-α in vivo induces lupus in pre-autoimmune lupus-prone NZB×NZW F1 (NZB/W) but not in BALB/c mice. In the current study, we show that in vivo expression of IFN-α induces sustained B-cell proliferation in both BALB/c and NZB/W mice. In NZB/W but not BALB/c mice, B-cell proliferation was accompanied by a rapid and unabated production of autoantibody-secreting cells (ASCs) in secondary lymphoid organs, suggesting that a B-cell checkpoint is altered in the autoimmune background. The majority (>95%) of ASCs elicited in IFN-α-treated NZB/W mice were short-lived and occurred without the induction of long-lived plasma cells. A short course of cyclophosphamide caused a sharp drop in IFN-α-elicited short-lived plasma cells, but the levels recovered within days following termination of treatment. Thus, our work provides new insights into effectiveness and limitations of the current SLE therapies.     

Sex differences in the regulation of experimentally induced autoantibodies in (NZB x NZW)F1 mice.

The ability to induce autoantibodies to erythrocytes in male and female (NZB x NZW)F1 mice was examined. Female (NZB x NZW)F1 mice were shown to produce significantly more autoantibody than the male (NZB x NZW)F1 mice. The regulation of this experimentaly induced autoantibody was studied by examining the ability of male and female (NZB x NZW)F1 mice to generate antigen-specific suppressor cells. A sex difference was found in the ability to generate these suppressor cells. Male mice generated antigen-specific suppressor cells in response to rat RBC which were capable to suppressing the experimental induction of red cell autoantibodies whereas female mice were unable to generate those antigen-specific suppressor cells.     

Genetic regulation of hypergammaglobulinaemia and the correlation to autoimmune traits in (NZB X NZW) F1 hybrid

To determine the inheritance patterns of both IgM class and IgG class hypergammaglobulinaemias, the locations of genes and the relations of these genes to other autoimmune traits in NZB X NZW (B/W) F1 hybrid, we measured serum levels of both IgM and IgG in NZB, NZW, B/W F1 hybrid, B/W F1 X NZW back-cross and B/W F1 X NZB back-cross mice. The highest serum IgM levels were observed in NZB mice, however the serum IgG levels were normal. In contrast, a large amount of IgG was produced in B/W F1 hybrids, in which the serum IgM levels were lower than those observed in NZB mice. The NZW mice had fairly normal values for both measures. Progeny studies suggested that a single dominant locus (Imh-1) of NZB strain, which is loosely linked to brown-black coat colour locus b and Mup-1 locus on chromosome 4, determines the IgM class hypergammaglobulinaemia. The estimated gene order was Mup-1:b:Imh-1. This IgM class hypergammaglobulinaemia in NZB mice was suppressed to a considerable extent in B/W F1 hybrid mice by either a gene dosage effect or more likely, a regulatory gene locus of NZW strain, being also loosely linked to Mup-1 locus on chromosome 4. As for the IgG class hypergammaglobulinaemia, a complementary effect of two or three genes, either one or two dominant genes derived from NZB and a single dominant gene from NZW strains, determines this trait in B/W F1 hybrid mice. There appeared to be no relationships between the genes responsible for the IgM class and IgG class hypergammaglobulinaemias. When looking at the correlations between the hypergammaglobulinaemias and the traits, anti-double stranded DNA (dsDNA) antibodies and renal disease in both back-cross mice, we found a significant quantitative correlation only between the IgG class hypergammaglobulinaemia and the IgG class anti-dsDNA antibodies in B/W F1 X NZB back-cross mice.     

Efficient in vitro amplification of a mouse-adapted scrapie prion protein

Protein misfolding cyclic amplification (PMCA) is a highly sensitive technique used to detect minute amounts of scrapie prion protein (PrP(Sc)), a major protein component of the infectious agents associated with prion diseases. Although exponential in vitro amplification of hamster scrapie PrP(Sc) has been established, the PMCA used was unsuccessful in achieving good amplification of PrP(Sc) from other animals. Here, we have investigated the cause of the insufficient PrP(Sc) amplification in mice and have developed an improved method suitable for amplification of the PrP(Sc) of the mouse-adapted scrapie prion strain Chandler. Mouse PrP(C), the cellular form of the prion protein, tends to become resistant to proteases during incubation independent of sonication. By adding digitonin to the reaction buffer as a lipid detergent, accumulation of the protease-resistant PrP(C) was inhibited; hence, mouse PrP(Sc) could be amplified to infinite levels. The present study is the first report describing effective amplification of PrP(Sc) of the mouse-adapted scrapie prion and this improved PMCA technique will contribute to prion research that uses mice as experimental animals.     

A versatile prion replication assay in organotypic brain slices

Methods enabling prion replication ex vivo are important for advancing prion studies. However, few such technologies exist, and many prion strains are not amenable to them. Here we describe a prion organotypic slice culture assay (POSCA) that allows prion amplification and titration ex vivo under conditions that closely resemble intracerebral infection. Thirty-five days after contact with prions, mouse cerebellar slices had amplified the abnormal isoform of prion protein, PrP(Sc), >10(5)-fold. This is quantitatively similar to amplification in vivo, but fivefold faster. PrP(Sc) accumulated predominantly in the molecular layer, as in infected mice. The POSCA detected replication of prion strains from disparate sources, including bovines and ovines, with variable detection efficiency. Pharmacogenetic ablation of microglia from POSCA slices led to a 15-fold increase in prion titers and PrP(Sc) concentrations over those in microglia-containing slices, as well as an increase in susceptibility to infection. This suggests that the extensive microglial activation accompanying prion diseases represents an efficacious defensive reaction.     

T-cell tolerance induction is normal in the (NZB x NZW)F1 murine model of systemic lupus erythematosus

The (New Zealand black (NZB) x New Zealand white (NZW))F1 (NZB/W) mouse strain spontaneously develops an autoimmune disease characterized by anti-dsDNA antibody production and glomerulonephritis. Although evidence suggests that production of pathogenic autoantibodies is T-cell dependent, the immunological defects that lead to activation of these autoreactive T cells are unknown. In particular, it has not been resolved whether autoreactive T cells become activated in these mice because of a generalized defect in T-cell tolerance induction. Previous work has demonstrated that thymic and peripheral tolerance to strongly deleting antigens are intact in NZB/W mice. In this study we investigate whether these mice possess a more subtle T-cell tolerance defect. To this end, we have produced NZB/W mice carrying a transgene encoding beef insulin (BI) which is expressed at levels close to the threshold for T-cell tolerance induction. In BALB/c mice this transgene produces a profound but incomplete state of BI-specific T-cell tolerance, mediated predominantly by clonal anergy. Comparison of BI-specific tolerance in NZB/W, major histocompatibility complex (MHC)-matched (BALB/c x NZW)F1, and BALB/c BI-transgenic mice clearly demonstrates that T-cell tolerance induction is normal in NZB/W mice. The data suggest that the loss of T-cell tolerance that ultimately supports nephritogenic autoantibody production in NZB/W mice does not result from a generalized defect in T-cell tolerance, and by extension likely results from aberrant activation of specific autoreactive T cells.     

Follicular dendritic cell dedifferentiation reduces scrapie susceptibility following inoculation via the skin

Transmissible spongiform encephalopathies (TSEs) are a group of subacute infectious neurodegenerative diseases that are characterized by the accumulation in affected tissues of PrP(Sc), an abnormal isoform of the host prion protein (PrPc). Following peripheral exposure, TSE infectivity and PrP(Sc) usually accumulate in lymphoid tissues prior to neuroinvasion. Studies in mice have shown that exposure through scarified skin is an effective means of TSE transmission. Following inoculation via the skin, a functional immune system is critical for the transmission of TSEs to the brain, but until now, it has not been known which components of the immune system are required for efficient neuroinvasion. Temporary dedifferentiation of follicular dendritic cells (FDCs) by treatment with an inhibitor of the lymphotoxin-beta receptor signalling pathway (LTbetaR-Ig) 3 days before or 14 days after inoculation via the skin, blocked the early accumulation of PrP(Sc) and TSE infectivity within the draining lymph node. Furthermore, in the temporary absence of FDCs before inoculation, disease susceptibility was reduced and survival time significantly extended. Treatment with LTbetaR-Ig 14 days after TSE inoculation also significantly extended the disease incubation period. However, treatment 42 days after inoculation did not affect disease susceptibility or survival time, suggesting that the infection may have already have spread to the nervous system. Together these data show that FDCs are essential for the accumulation of PrP(Sc) and infectivity within lymphoid tissues and subsequent neuroinvasion following TSE exposure via the skin.     

Requirement of H-2 heterozygosity for autoimmunity in (NZB X NZW)F1 hybrid mice

In the F1 hybrid of autoimmune New Zealand Black (NZB) and phenotypically normal New Zealand White (NZW) mice, there occurs a severe systemic lupus erythematosus (SLE)-like autoimmune disease more fulminant than that found in the parental NZB mice. To determine the role of the H-2 complex in the pathogenesis of autoimmune disease of the (NZB X NZW)F1 hybrid, we developed H-2-congenic NZB (NZB.H-2z) and NZW (NZW.H-2d) strains, and compared the degree of autoimmune features between congenic H-2d/H-2d and H-2z/H-2z homozygous F1 hybrids and the original H-2d/H-2z heterozygous (NZB X NZW)F1 hybrid. We found that autoimmune features such as productions of IgG class anti-DNA antibodies and retroviral gp70 immune complexes and the development of renal disease were to a great extent reduced in both H-2 homozygous F1 hybrids, as compared with the H-2 heterozygous (NZB X NZW)F1 hybrid. It would thus appear that the heterozygosity of H-2d haplotype derived from NZB and H-2z from NZW is essential for the autoimmune disease characteristic of the (NZB X NZW)F1 hybrid.