Analysis of autoantibodies to glycolipids on thymocytes in New Zealand black mice.

Carbohydrate specificities of thymocyte cytotoxic autoantibodies in New Zealand Black (NZB) mice were examined using liposome immune lysis assay (LILA) system. NZB mice progressively produced antibodies to nine neutral glycolipids and two gangliosides tested by 10 months of age. Such increases were not detected in normal BALB/c and CBA/J mice. Among these antibodies, antibodies to ceramide monohexoside (CMH), ceramide dihexoside (CDH), paragloboside (PG), ceramide pentahexoside (CPH), asialo GM1 (GA1), asialo GM2 (GA2), GM4 and GM2 in the plasma of NZB mice were absorbed by single cell suspensions of autologous untreated as well as protease-treated thymocytes. In contrast, antibodies to ceramide trihexoside (CTH), globoside (Glo), and Forssman antigen (For) were not absorbed by these cells. Analysis of glycolipid compositions of young NZB thymocytes demonstrated that strict correlation was observed between the presence of glycolipids on thymocytes and absorbing pattern of anti-glycolipid antibodies by thymocytes. These data indicate that anti-carbohydrate antibodies with thymocyte binding capacity in NZB mice mainly recognize sugar portions of glycolipids rather than glycoproteins on thymocytes. The failure to find such carbohydrate specific antibodies in some normal strains of mice suggested that these antibodies may be important for subsequent immunologic abnormalities in NZB mice.     

Suppression of in vivo granulopoiesis by anti-asialo GM1 serum

In vivo effects of anti-asialo GM1 (GA1) serum on hemopoiesis were studied by morphological examination of the blood, bone marrow, and spleen and by measuring the number of granulocyte-macrophage colony-forming units (CFU-GM) per femur after injecting of the anti-serum into mice intraperitoneally. The number of circulating lymphocytes markedly decreased 2 days after injection and then recovered, but circulating granulocytes gradually declined and reached a nadir at 6 days, then rapidly recovered. Granulopoietic activity in the bone marrow was reduced on day 2, but recovered profusely from day 4, followed by marrow neutrophilia on day 10. The spleen showed marked extramedullary granulopoiesis on days 6 and 10. CFU-GM per femur increased by 24 hours, reaching a maximum value 250% of normal on day 3, then returned to the normal level. CFU-GM growth was not affected by the treatment of anti-GA1 serum plus complement in vitro. These results suggest that the proliferating compartment of the myeloid series in the bone marrow was eliminated by anti-GA1 serum injection that led to a decrease in granulocytes and an increase in CFU-GM.     

Auto-MHC class II-reactive T cell line obtained from MRL/+mice suffering from "lpr-GVHD". I. Characterization of surface phenotypes, specificities and functions in vitro

When MRL/Mp-(+)/+ (MRL/+) mice are lethally irradiated and then reconstituted with bone marrow or spleen cells from MRL/Mp-lpr/lpr (MRL/lpr) mice, they develop a graft-versus-host disease (GVHD)-like syndrome, colloquially known as "lpr-GVHD". To analyze the roles of the MRL/lpr T cells in the development of "lpr-GVHD" and autoimmune diseases, several T cell lines were established from the spleen cells of MRL/+ mice suffering from "lpr-GVHD". The surface phenotypes, specificities, and functions of a representative clone (l/+T1) of the cloned T cell lines were characterized. The l/+T1 cells showed Thy-1.2+, L3T4+ and T3+, but Lyt-2- and B220- phenotypes. Proliferative response was observed by co-culturing the cells with spleen cells from MRL/+, MRL/lpr, AKR/J, and C3H/HeN mice, but not from BALB/c or C57BL/6 mice. Furthermore, the l/+ T1 cells responded to spleen cells of B10.BR and B10.A but not B10.D2 mice. The proliferative response of l/+ T1 cells to MRL/+ spleen cells was inhibited by anti-I-Ek (but not anti-I-Ak or anti-Kk) antibodies, suggesting that the specificity of l/+T1 cell culture enhanced the proliferative response only in the presence of appropriate stimulators. Treatment of stimulator cells with J11d.2 + C (but not anti-Thy-1.2 + C or 33D1 + C) abolished the stimulatory effect, indicating that B cells are effective stimulator cells for auto-MHC class II-reactive l/+T1 cells. When MRL/+ splenic B cells were co-cultured with l/+T1 cells, both B cell proliferation and IgM production were observed. In addition, IgM-class rheumatoid factor and anti-ssDNA antibody activities were found in the supernatants of MRL/+ splenic B cells co-cultured with l/+T1 cells. These results are discussed in relation to "lpr-GVHD" and autoimmunity in MRL/lpr mice.     

IgG anti-cardiolipin antibodies in murine lupus

The frequency and nature of IgG anti-cardiolipin and anti-ds-DNA antibodies among MRL/lpr, MRL/+ and NZB/W F1 mice (murine lupus strains) and non-autoimmune inbred strains of mice (NIH/Swiss and Balb/c) were analysed by ELISA. High titres of anti-ds-DNA were detected in autoimmune strains (MRL/lpr, 69%; MRL/+, 50%; and NZB/W, 80% positive), whereas anti-cardiolipin antibodies were detected only in MRL/lpr (69%) and MRL/+ (17%) mice. IgG subclass analysis of these antibodies in 20 MRL/lpr sera revealed that all four subclasses were represented. When tested for fine antigenic specificity, anti-cardiolipin antibodies in MRL/lpr and MRL/+ mice bound to acidic phospholipids rather than to neutral phospholipids and were not inhibited by DNA. In MRL/lpr mice, anti-cardiolipin antibodies were first detected at 2 months, peaked around 5 months and then declined preterminally. To determine whether complications associated with anti-cardiolipin antibodies were present in MRL/lpr mice, blood counts were performed and litter sizes were determined. Although no significant decreases in the red and white blood cell counts were observed in MRL/lpr mice, platelet counts were significantly lower compared with NIH/Swiss (P < 0.001) and Balb/c (P < 0.005) mice. MRL/lpr mice had significantly fewer pups per delivery compared with a normal strain (MRL/lpr, 5.3+2.6; NIH/Swiss, 72 +/- 2.1; P < 0002). These observations indicate that the serological characteristics of IgG anti-cardiolipin antibodies in MRL/ lpr mice are similar to those of anti-cardiolipin antibodies in humans with lupus. Whether these autoantibodies are pathogenetically related to thrombocytopenia and a small litter size in MRL/lpr mice remains to be determined.     

Accelerated expression of anti-Sm and Y2 idiotype differ in dependence on T cell subsets in MRL/+ mice.

We investigated the role of MRl T cells in the induction of anti-Sm antibodies and Y2 idiotype. Four injections of Sm antigen in Freund's complete adjuvant were required to induce peak amounts of specific anti-Sm antibody in young BALB/c and MRL/+ mice. The Y2 idiotype was expressed in MRL/+ mice but not in BALB/c mice. Expression of both anti-Sm, predominantly IgG2a heavy chain, and Y2 idiotype was augmented in MRL/+ mice after two injections of Sm if, prior to immunization, mice received splenic T cells from naive MRL/lpr or immunized, but not naive MRL/+ mice. These results suggest that the lpr gene contributes to the ability of autoimmune T cells to augment the anti-Sm antibody response. Treatment of primed MRL/+ donor T cells with anti-CD4, but not anti-CD8, antibodies and complement removed the ability to augment anti-Sm antibody production. In contrast, augmentation of Y2 idiotype production was abrogated by pretreatment of donor T cells with either anti-CD4 or anti-CD8. These results suggest that, while MRL/+ CD4+ T cells play an important role in anti-Sm antibody production, additional interaction between CD4+ and CD8+ T cells augments Y2 expression.     

Auto-MHC class II-reactive T cell line obtained from MRL/+ mice suffering from lpr-GVHD. II. Analyses of functional characteristics of T cell line by in vivo administration.

Functional characteristics of an autoreactive (I-Ek-restricted) T cell line (l/+ T1), previously established from MRL/M(p-)+/+(MRL/+) mice with lpr-GVHD, were analyzed in vivo. Intravenous injection of l/+ T1 cells to non-irradiated H-2k (MRL/+ or AKR) mice (but not H-2d mice) induced enhanced spontaneous proliferation of recipient spleen cells; this was also I-Ek self-restricted. This augmented self-reactivity seemed to be mediated by recipient L3T4+ T cells, since few l/+ T1 cells were detected in the spleen cells of l/+ T1-injected AKR mice by cell surface marker analyses, and the treatment of the spleen cells with anti-Thy-1.1 antibody (Ab) or anti-L3T4 Ab plus complement abolished this enhanced spontaneous proliferation. The production of IgM rheumatoid factor (RF) in AKR mice and IgG RF in MRL/+ mice increased, although no enhancement of anti-ssDNA Ab production was observed. Judging from both spleen B cell proportion and serum Ig levels, autoantibody induction by the injection of l/+ T1 cells was not associated with polyclonal B cell activation. When lethally irradiated B10 congenic mice were used as recipients, B10. BR mice showed elevated levels of IgM anti-ssDNA and IgM RF 1 wk after l/+ T1 cell injection; it is likely that lethal irradiation causes autoantigens, particularly DNA, to be exposed. These findings suggest that the autoreactivity of l/+ T1 cells can be transferred to recipient L3T4+ T cells via T-T interaction or the immunological network, and that increased autoreactivity induces autoantibody production in the presence of autoantigen stimulation. In contrast to the stimulatory effects observed in AKR and MRL/+ mice, MRL/Mp-lpr/lpr(MRL/lpr) mice showed a different response to the injection of l/+ T1 cells; spontaneous proliferation of spleen cells and autoantibody production were not enhanced, and suppression of the mitogen responses was observed. It is discussed that lpr-GVHD may be due to these unusual features of MRL/lpr mice.     

MRL/MpJ-Faslpr mice show abnormalities in ovarian function and morphology with the progression of autoimmune disease

Abstract

The immune system is known to affect reproductive function, and maternal–fetal immune tolerance is essential for a successful pregnancy. To investigate the relationship between autoimmune disease and female reproductive function, we performed a comparative analysis of the ovarian phenotypes for C57BL/6 mice, autoimmune disease-prone MRL/MpJ (MRL/+) mice and congenic MRL/MpJ-Fas^lpr (MRL/lpr) mice harboring a mutation in the Fas gene that speeds disease onset. Both MRL-background strains showed earlier vaginal opening than C57BL/6 mice. The estrous cycle became irregular by 6 and 12 months of age in MRL/lpr mice and mice of the other two strains, respectively. Histological analysis at 3 months revealed that the number of primordial follicles was smaller in MRL-background mice than in C57BL/6 mice after 3 months. In addition, MRL/lpr and MRL/+ mice displayed lower numbers of ovarian follicles and corpora lutea at 3 and 6 months, and 6 and 12 months, respectively, than that in age-matched C57BL/6 mice. MRL/lpr and MRL/+ mice developed ovarian interstitial glands after 3 and 6 months, respectively. In particular, MRL/lpr mice showed numerous infiltrating lymphocytes within the ovarian interstitia, and partially stratified ovarian surface epithelia with more developed microvilli than that observed in C57BL/6 mice at 6 months. No significant differences in serum hormone levels were observed between the strains. In conclusion, MRL/lpr mice display altered ovarian development, morphology and function consistent with the progression of severe autoimmune disease, as these findings are less severe in MRL/+ counterparts.     

Unusual cell surface properties of the T lymphocyte population expanding in MRL/Mp-lpr/lpr mice.

MRL/Mp-lpr/lpr (lpr/lpr) mice but not the congenic MRL/Mp-+/+ (+/+) mice, develop a generalized lymph node (LN) hypertrophy reflecting the expansion of a T-cell population that acts as an enhancing factor for autoimmunity. In order to characterize better this T-cell population, we investigated some of its surface properties in comparison with those of +/+ T cells. Electrophoretic measurements revealed that lpr/lpr T cells possess a lower electronegative surface charge than %/% T cells which indicates that the two cell types differ in the molecular composition of their plasmic membrane periphery. This notion was substantiated by the quantification of T- and B-cell markers and of lectin-binding sites on these cells using single- and two-colour flow cytofluorimetry. In agreement with recent observations by Lewis, Giorgi & Warner (1981) lpr/lpr T cells exhibited lower levels of Thy-1 and Lyt-1 antigens than +/+ T cells and were mostly devoid of Lyt-2 antigen. Although lpr/lpr lymph node (LN) cells displayed similar amounts of surface receptors for peanut agglutinin as +/+ LN cells, the expression of surface receptors for other lectins were either lower (Limulus polyphemus agglutinin, Maclura pomifera agglutinin, Concanavalin A) or higher (Helix pomatia agglutinin, Soya bean agglutinin, Bandeiraea simplicifolia agglutinin I, Phytohaemagglutinin L) on lpr/lpr T cells than on +/+ T cells. These data indicate that the T cells accumulating in hypertrophied lpr/lpr LN are endowed with unique surface characteristics which may explain some of the functional abnormalities of these cells.     

Significant role of Fas ligand-binding but defective Fas receptor (CD95) in lymph node hyperplasia composed of abnormal double-negative T cells

The functional differences between two mutations of the Fas (CD95) locus, Faslpr (lpr) and Faslprcg (lprcg), were investigated using bone marrow (BM) transplantation on the C3H mouse background. Both lpr/lpr and lprcg/lprcg BM transferred caused lymph node (LN) hyperplasia in lpr/+ and lprcg/+ recipients, although it was clearly smaller than that in lpr/lpr and lprcg/lprcg recipients of lpr/lpr and lprcg/lprcg BM. In addition, both BM induced significantly larger LN hyperplasia in lprcg/+ than lpr/+ recipients. Appearance of CD4- CD8-[double negative (DN)] T cells in the periphery is the most consistent phenotype of Fas mutations. Importantly, the proportion of DN T cells was higher in larger LN hyperplasia in the order of lpr/+, lprcg/+ and lpr/lpr or lprcg/lprcg recipients. On the other hand, both lpr/lpr and lprcg/lprcg BM transferred into wild-type (+/+) mice caused marked LN atrophy. The former, but not the latter, induced wasting syndrome. Faslg1d (gld)-homozygous lpr/lpr BM transferred into +/+ mice elicited LN hyperplasia of the same extent as that in lpr/lpr mice transferred with lpr/lpr BM, but not wasting syndrome. Taken together with the fact that DN T cells massively express Fas ligand (FasL), this study implied that FasL overexpressed on DN cells may be involved in the accumulation of DN T cells in LN, LN atrophy and wasting syndrome, and that lprcg Fas, which can bind to Fas ligand but not transduce apoptosis signal into cells, may modulate these pathological conditions by interfering with the binding of FasL to Fas.     

Follicular dendritic cell dysfunction and disorganization of lymphoid structures in MRL/lpr mice.

The follicular dendritic cell (FDC) in secondary lymphoid organs plays a key role in the function of the germinal center (GC) of the lymphoid follicle (LF) for regulation of the humoral immune response. MRL MpJ-lpr/lpr (MRL/lpr) mice, which have an abnormal humoral immune response, are a model for autoimmune disease. The present study was undertaken to investigate FDC dysfunction and LF disorganization in the spleen and lymph nodes of MRL/lpr mice. In 12-week-old MRL/lpr mice, antigen (Ag) trapping of FDC and half-life of trapped Ag on FDC was reduced. Although immunohistochemistry revealed well-developed FDC networks positive for complement receptors and having in vitro immune complex trapping in cryostat sections, Ag-trapping was not detected in 16-week-old MRL/lpr mice. Moreover a marked decrease in the number of GC and that of GC cell of residual GC in the MRL/lpr mice was observed by 12 weeks of age. Also reduced expression of intercellular adhesion molecule-1, FcgammaRII/III, and FDC-specific Ag (FDC-M1) on FDC was detected in 16-week-old MRL/lpr mice. The accumulation of double negative (CD4-CD8-) T cells, which is a characteristic feature of MRL/lpr mice, was observed around LF; however they did not infiltrate the LF and FDC network. In conclusion the loss of Ag-trapping on FDC and simultaneous disorganization of the lymphoid structure may be related closely to the immunologic abnormality observed in MRL/lpr mice.     

Functional deficiencies of spleen dendritic cells in autoimmune MRL/lpr mice

We investigated functional aspects of splenic dendritic cells (DC) obtained from MRL/MpJ-lpr/lpr (MRL/l) mice, and their normal counterparts, MRL/MpJ-+/+ (MRL/+) mice. In vitro antigen-presenting activity of DC obtained from MRL/l mice was impaired compared with that of DC from MRL/+ mice. Another major functional aspect of DC, i.e., stimulator cell activity in the allogeneic mixed lymphocyte reaction (MLR), was also found to be impaired in MRL/l mice. MRL/l mice and MRL/+ mice were also examined for co-operation between macrophages (M luminal diameter) and DC. We found peritoneal resident M luminal diameter obtained not only from MRL/+ mice but also from MRL/l mice released a soluble factor which enhanced the activity of DC from the respective mice. Furthermore, DC from both MRL/l and MRL/+ mice responded to the culture supernatant of a mouse macrophage hybridoma clone, S44, which releases a factor that enhances the antigen-presenting activity of DC, and their activity as stimulator cells in the allogeneic MLR was enhanced. However, the degree of enhancement was less in MRL/l mice than in MRL/+ mice.     

Interstitial pneumonitis in autoimmune MRL/lpr mice and its treatment with cyclosporin A

Age-associated changes of anti-double-stranded (ds) DNA antibodies, anti-single-stranded (ss) DNA antibodies, and serum immune complex concentrations were studied in MRL/lpr mice. All anti-ds DNA antibodies, anti-ss DNA antibodies, and immune complexes began to be detected in the sera of MRL/lpr mice aged 8 to 13 weeks and increased remarkably after 17 weeks of age. Almost no pathological findings were observed histologically in the lungs of MRL/lpr mice aged 8 weeks but interstitial pneumonitis became evident at 14 weeks of age. Peribronchial and perivascular lymphocyte infiltrations were seen in the lungs of 14-week-old MRL/lpr mice and became more severe at 21 weeks of age. Oral administration of cyclosporin A to 15-week-old MRL/lpr mice markedly prolonged their life span. The lungs of 44-week-old MRL/lpr mice given cyclosporin A showed few pathological findings except for minimal perivascular lymphocyte infiltration.     

Interleukin-1 Contributes to High Level IgG Production in the Murine MRL/Ipr Lupus Model

The autoimmune syndrome in MRL/lpr mice resembles human lupus, both in its serologic and immunopathologic characteristics. The contribution of IL-1 to high-level Ig production in the MRL/lpr model is poorly understood. We investigated the effect of treating B-cell-enriched, or, B plus T cell suspensions derived from either pre-disease or diseased lupus-prone MRL/lpr mice with IL-1ß or IL-1 receptor antagonist (IL-1Ra). Disparate patterns of IgG production by B cells and B plus T cells derived from diseased versus pre-diseased MRL/lpr mice was observed following treatment with IL-1ß. Remarkably, IL-1ß caused significant suppression in IgG production by B cells derived from diseased MRL/lpr mice as compared to B cells derived from pre-disease mice. In mix-and-match experiments with B plus T cells from pre-disease and diseased MRL/lpr mice, both T cell help and B cell hyperactivity, originating in diseased MRL/lpr mice were found to be important factors in high-level IgG production in diseased MRL/lpr mice. Furthermore, IL-1Ra treatment of B plus T cell co-cultures derived from diseased MRL/lpr mice was able to significantly suppress IgG production, whereas, IL-1Ra treatment of B plus T cell co-cultures derived from pre-disease MRL/lpr mice demonstrated virtually no suppression in IgG production. Collectively, these results indicate a potentially important but complex role for IL-1 in influencing high-level IgG production in MRL/lpr mice with established disease.     

Anti-nRNP anti-nuclear antibody-secreting cells are represented in the B-lymphocyte repertoire of normal and MRL/MP-lpr/lpr lupus mice.

Spleen cells from MRL-lpr/lpr, CBA and BALB/c mice were cultured in vitro and assayed for production of anti-nuclear antibodies. Spleen cells from all species produced IgM antibodies to a nRNP (U1-RNP)-specific antigen and to double-stranded DNA (dsDNA) after stimulation with LPS. The specificity of the anti-nRNP antibodies was shown, by immunoblotting, to be directed against the 33,000 MW polypeptide of nRNP/Sm. CBA mice produced more IgM autoantibody in vitro than MRL/lpr or BALB/c mice. In contrast, IgG anti-nRNP and anti-dsDNA antibody were not produced by any of the strains. Our data show that anti-nRNP and anti-dsDNA precursor B cells are part of the normal murine immune repertoire and are not confined to the MRL/lpr strain. This suggests that the spontaneous development of anti-nRNP and anti-dsDNA antibodies associated with systemic lupus erythematosis (SLE) is dependent on clonal stimulation and removal of suppressive influences.     

A glycolipid on the surface of mouse natural killer cells

Cytotoxic treatment with rabbit antiserum raised against purified glycosphingolipid “asialo GM1” was capable of eliminating natural killer (NK) activity of spleen cells from different inbred mouse strains including CBA/J, C57BL/6, BALB/c, AKR, and athymic nude mice. The anti-asialo GM 1 antiserum showed little cross-reactivity with structurally related glycolipids, e.g. GM 1, GD 1 b and asialo GM 2 in the microflocculation test. The specific reactivity of this antiserum with NK cells was confirmed by the quantitative absorption of anti-NK activity with graded amounts of asialo GM 1 but not with other glycosphingolipids. The absorption of anti-brain-associated T cell antigen (anti-BAT) with asialo GM 1 also effectively diminished its anti-NK activity, leaving the ability to kill T cells intact. This suggests that the antibody to asialo GM 1 is responsible for the anti-NK activity contained in the anti-BAT antiserum. In contrast to the extreme sensitivity of NK cells to anti-asialo GM 1, alloreactive cytotoxic T killer cells generated in the mixed lymphocyte culture were not killed by anti-asialo GM 1 and complement. These results indicate that asialo GM 1 is expressed on mouse NK cells in a high concentration.     

Expression of Heterozygous lpr Gene in MRL Mice

The presence of the homozygous lpr gene (lpr/lpr) in MRL mice has been regarded as mandatory for the development of the early onset of lupus disease, T-cell dysfunction, and polyclonal B-cell activation. Congeneic MRL mice lacking the lpr gene (MRL +/+) display neither the lupus disease nor the immunological abnormalities within the first year of life. In this study we examined the cellular functions of MRL mice heterozygous at the lpr locus. The results indicate that MRL mice heterozygous at the lpr locus display intermediate delayed-type hypersensitivity compared with homozygous lpr/lpr mice on the one hand and congeneic +/+ mice on the other. Furthermore, proliferative responses to concanavalin A, measured by uptake of [3H]thymidine, were significantly lower in MRL mice heterozygous at the lpr locus than in +/+ mice, but significantly higher than in homozygous MRL lpr/lpr mice. Polyclonal B-cell activation, assessed by measurement of frequencies of IgG-secreting spleen cells, a prominent feature in MRL lpr/lpr mice, was significantly lower in lpr/+ mice and totally absent in +/+ mice. Furthermore, spleen cells spontaneously secreting auto-antibodies were found in large numbers in MRL lpr/lpr mice and in considerably lower but still significant numbers in heterozygous MRL +/lpr mice. In contrast, spleen cells from matched MRL +/+ mice did not display any spontaneous autoantibody production. Taken together, these data provide evidence for immunomodulatory properties of the heterozygous lpr gene.     

Immune complex-degradation ability of macrophages in MRL/Mp-lpr/lpr lupus mice and its regulation by cytokines.

Impaired clearance of circulating and/or deposited immune complexes (IC) by the mononuclear phagocytic system is one of the major factors in the pathogenesis of IC diseases. MRL/Mp-lpr/lpr (MRL/lpr) lupus mice spontaneously develop a lethal glomerulonephritis associated with IC deposition. The ability of macrophages to degrade phagocytozed IC and regulation of this degradation in MRL/lpr mice were examined. In 4-month-old MRL/lpr mice, macrophages accumulated in the affected glomeruli and these macrophages contained many phagosomes containing electron-dense bodies. When culture supernatant of human T cell line HUT102 was administered intraperitoneally into disease-bearing MRL/lpr mice, degradation of these electron-dense bodies in the macrophages in glomeruli was noted. We developed a quantitative in vitro assay for IC degradation activity of MRL/lpr resident peritoneal macrophages (RPM) using peroxidase-labelled IC derived from MRL/lpr mouse sera. The ability of the RPM to degrade IC was remarkably enhanced by the pretreatment with HUT102 cell products and the related human recombinant cytokines, lymphotoxin and IL-1 alpha. Moreover, pretreatment of RPM from non-diseased MRL/Mp-+/+ mice with the culture supernatant of spleen cells from diseased MRL/lpr mice reduced their IC degradation activity. These results suggested that the ability of macrophages to degrade IC in MRL/Mp strains of mice is under the regulation of cytokines, and the impaired ability in the disease-bearing mice may be the result of abnormalities in the cytokine system in these mice.     

Long term administration of cyclophosphamide in MRL/1 mice. I. The effects on the development of immunological abnormalities and lupus nephritis

Weekly injection of cyclophosphamide (Cy) into MRL/Mp-lpr/lpr (MRL/l) mice, at a dose of 10-20 mg/kg, from 1 month of age prevented the development of generalized lymph node enlargement, decreased serum levels of anti-DNA antibodies and immune complexes, and markedly prolonged their life span. Cy effectively suppressed enhanced differentiation of B cells, as evidenced by decreased number of immunoglobulin secreting cells in the spleen. Cy was also shown to suppress abnormal expansion of Thy-1 positive cells in lymphoid organs of MRL/1 mice. These results suggested that Cy prevented the development of murine lupus like syndrome in MRL/1 mice through suppression of spontaneous polyclonal B cell activation and also by reducing the number of T cells to exert excessive helper activity on B cells.     

Enhancement of the activities of glycosyltransferases involved in the biosynthesis of mucin-type sugar chains in autoimmune MRL lpr/lpr mouse T cells

Lymph node (LN) T cells from autoimmune MRL/MpJ-lpr/lpr (lpr) mice and control MRL/MpJ-+/+ (+/+) mice were compared as to their cell surface lectin-binding sites and glycosyltransferase activities. T cells from enlarged LN of lpr mice expressed a higher amount of binding sites for lectins reactive to mucin-type sugar chains than normal +/+ mouse T cells. Correspondingly, glycosyltransferase activities involved in the biosynthesis of mucin-type sugar chains were higher in lpr mouse T cells than in +/+ T cells. The activities of UDP-N-acetylgalactosamine (GalNAc):polypeptide GalNAc transferase and UDP-galactose (Gal):asialo bovine submaxillary mucin (BSM) Gal transferase were found to be elevated. The activity of UDP-Gal:asialo-agalacto transferrin Gal transferase, which is involved in the biosynthesis of complex type sugar chains, was also increased in lpr mice but to a smaller extent than the mucin-type Gal transferase activities. An abnormality in sialyltransferase activity was also found in lpr T cells.     

Decay-accelerating factor ameliorates systemic autoimmune disease in MRL/lpr mice via both complement-dependent and -independent mechanisms

Decay-accelerating factor (DAF) is a glycosylphosphatidylinositol-anchored membrane protein that restricts complement activation on autologous cells. Previous studies have established a significant protective activity of DAF in the MRL/lpr murine model of human systemic lupus erythematosus. To dissect the mechanism of protection by DAF in this disease model, we evaluated the effect of C3 gene ablation on disease development in MRL/lpr-Daf-1(-/-) mice. We found no significant difference in lymphadenopathy, splenomegaly, or anti-chromatin autoantibody titer between complement-sufficient and complement-deficient MRL/lpr-Daf-1(-/-) mice. On the other hand, complement deficiency strikingly reduced the incidence and severity of dermatitis in MRL/lpr-Daf-1(-/-) mice. To assess the contribution of DAF expression on lymphocytes versus local tissues in suppressing dermatitis, we generated BM chimeric mice between MRL/lpr-Daf-1(-/-) and MRL/lpr-Daf-1(+/+) mice. Compared with MRL/lpr-Daf-1(-/-) --> MRL/lpr-Daf-1(-/-) controls, MRL/lpr-Daf-1(-/-) --> MRL/lpr-Daf-1(+/+) chimeras developed significantly attenuated dermatitis, suggesting that the protective effect of DAF in suppressing dermatitis is primarily attributable to its local expression. We conclude that DAF works as a complement regulator in the skin to protect MRL/lpr mice from skin inflammation, whereas its inhibitory role in the induction phase of MRL/lpr autoimmunity is complement-independent. Together, these results reveal multiple mechanisms of action for DAF in ameliorating systemic autoimmunity.