Life-span, spontaneous disease and immunology
Develops autoimmune haemolytic anaemia of the Coombs-positive, warm antibody type (Simpson, 1976; Howie and Simpson, 1974) as well as a nephropathy which is variable in expression and unpredictable in progress, but is probably an immune-complex-induced glomerulonephritis. Burnet (1972a, b) considered that at least two genes are involved, one of which is also present in NZC. Genetic linkage to chromosomes 1, 4, 7, 10, 13 and 19 imply that multiple genes in different combinations contribute to the severe renal disease (Drake et al, 1995).
A virus may also be involved, although Simpson (1976) considered that: `. . .the case for a viral aetiology is unproven, although the possibility exists that virus may be present in incomplete form'. According to Burnet, NZB mice have an abnormally high immunological vigour and resistance to induction of immunological tolerance or paralysis, which is manifested before the animals become Coombs-positive. The condition may be transferred to young isogenic mice by cells from the spleen, but not from other lymphoid organs. Thus, the condition appears to depend on stem cells of immunocyte lines. Autoimmune plaque-forming cells, active against mouse erythrocytes, are present in old mice. Onset and severity of the condition can be influenced by diet (Fernandes et al., 1972., 1972). Theofilopoulos et al (1980) have compared immune function in this and other autoimmune strains. Only NZB splenic lymphocytes from autoimmune donors inoculated into pre-autoimmune NZB or in BALB/c mice could evoke a positive Coombs test (Jenkinson and East (1980). Diethyldithiocarbamate (DTC), an immunomodulative agent which may enhance T cells, prolongs life in autoimmune MRL-lpr/lpr mice, but not in autoimmune NZBxNZWF1 hybrids (Halpern and Yocum 1991). Defect in the expression of the alloantigen, Ly6C, which is not detectable on spleen or lymph node cells (c.f. NOD and ST but contrast most other strains) and may be due to an interruption in the flanking region of the Ly6C gene at a point 475 bp upstream of the transcription initiation site, as found in NOD (Philbrick et al 1990). Ultrastructural pathology of the thymic reticulum revealed several features in common with BXSB and MRL-lpr in varying degrees according to sex and age of the mice. Main anomalies included vacuolized aspect of the thymic epithelium, an increased number of macrophages, interdigitating cells and cystic cavities, the presence of a great number of plasmocytes and mastocytes and extensive interstitial fibrosis and arteriosclerosis. The most intriguing finding was the presence of crystal-like inclusions in epithelial cells (Nabarra et al 1990). Natural autoantibodies are involved in the heamolytic anaemia (Hentati et al, 1994).
Pure-line mice have a high level of natural thymocytotoxic autoantibodies (Auer et al., 1974., 1974), a low immune response to Dextran (cf. 6/10) (Blomberg et al., 1972., 1972), a low lymphocyte phytohaemagglutinin response (30/43) (Heiniger et al., 1975., 1975), a high 25% incidence of serum antinuclear factor (4/17) (Barnes and Tuffrey, 1967) and a poor immune response to DNP-keyhole limpet haemo-cyanin (9/11) (Borel and Kilham, 1974), and are discriminators between `H' and `L' sheep erythrocytes (cf. 12/18) (McCarthy and Dutton, 1975). Mean life-span short (2/17 = 459 days in males, 441 days in females) in SPF fostered conditions (Festing and Blackmore, 1971). Median life-span short (4/4 = 280 days males, 4/4 = 270 days females) (Stutman, 1974). Males resistant but females more susceptible to immunosuppression of contact hypersensitivity by ultraviolet B light (Noonan and Hoffman, 1994)
Hypertrophy of the pituitary in 80% of survivors to 1 year and pituitary tumours in 25% of aged breeders (Russfield, 1966).
Hybrids with NZB
In hybrids with C57BL there is a late-appearing positive direct Coombs test. Hybrids with NZW develop an autoimmune disease resembling human systemic lupus erythematosus (Talal et al., 1972., 1972), with high titres of natural thymocyto-toxic autoantibody in many animals (Shirai and Mellors, 1972). NZBxNZWF1 hybrid B cells apparently differ from normal murine B cells in their capacity to produce IgG antibodies upon T cell-dependent antigenic stimulation. (Riley et al 1991). Genetic analysis of a backcross to NZW shows that one set of loci regulate serum levels of IgG antibodies to double-stranded DNA, single-stranded DNA, total histones and chromatin, and these overlap with loci that control autoantibodies to the viral glycoprotein gp70. These latter loci are most strongly linked with renal disease. A locus on distil chromosome 4 was linked with nephritis but not with any of the autoantibodies measured (Vyse et al, 1996). Daily intraperitoneal injections of DNase from 4-7 months of age resulted in reduced proteinuria and serum creatinine and strikinly less severe renal pathology (Macanovic et al, 1996). Autoimmunity is associated with increased anxiety and less exploratory behaviour (Schrott and Crnic, 1996). Caloric restriction and supplementation with fish oil increases life span and diminishes histological evidence of glomerulonephritis. This is associated with decreased expression of platelet-derived growth factor-A (Troyer et al, 1997)..
Other characteristics
High balsa-wood gnawing activity (12/16) (Fawdington and Festing 1980). High coumarin hydroxylating ability (cf. 4/13) (Lush and Arnold, 1975). Pentobarbital i.p. induces hepatic epoxide hydrase (cf. 4/7) (Oesch et al., 1973., 1973). Sensitive to lethal effects of ozone (2/21) (Goldstein et al., 1973., 1973). Mineral oil injected i.p. induces plasmacytomas (Potter, 1972). High plasma triglyceride (9/11) and cholesterol (11/11) levels (Jiao et al 1990).
Susceptible to mouse hepatitis virus type 3 infection (cf. 5/14) (Le Prevost et al., 1975., 1975). No transmission of murine leukaemia virus (Scripps) to succeeding generations (Jenson et al., 1976., 1976). Carries no detectable endogenous ecotropic MuLV DNA sequences (Jenkins et al 1982). In contrast to ten other strains, it does not carry type I and II endogenous type-c viruses (cf. SWR) (Stephenson et al., 1975., 1975). Totally refractory to infection by Leishmania tropica parasite (Howard et al 1980i0 1980) and to Leishmania major mexicana (Lazama-Davila, 1997). Low immune response to ganglio-series gangliosides (c.f. 4/10) Kawashima et al (1992).
About 30-40% develop neocortical ectopias due to a recessive gene with incomplete penetrance (Sherman et al, 1994)
Poor reproductive performance (24/25). Litter size 3.8 at weaning, colony output 0.5 young/female/week (Festing, 1976a). First litter size high (1/6) but fourth litter low (6/6). Low proportion of females produce four or more litters (6/6) and low percentage of fertile matings (6/6) (Fernandes et al., 1973., 1973). Intermediate breeding performance (17/24) (Hansen et al., 1973., 1973). High bone density of femur (2/11) (Beamer et al, 1996).
Bielschowsky M. and Goodall C. M. (1970) Origin of inbred NZ mouse strains. Cancer Res. 30, 834-836.
Simpson L. O. (1976) An NZB virus or NZB mice with viral infections? Lab. Anim. 10, 249-260.
Stutman O. (1974) Cell-mediated immunity and aging. Fed. Proc. 33, 2028-2032.
Mouse Genome Database (MGD), Gene Expression Database (GXD), Mouse Models of Human Cancer database (MMHCdb) (formerly Mouse Tumor Biology (MTB)), Gene Ontology (GO) |
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