MRL/lpr-->severe combined immunodeficiency mouse allografts produce autoantibodies, acute graft-versus-host disease or a wasting syndrome depending on the source of cells

Mature dendritic cells readily break tolerance in normal mice but do not lead to disease expression

OBJECTIVE

To examine the ability of mature dendritic cells (DCs) or macrophages intentionally exposed to lipopolysaccharide or apoptotic or necrotic cells to break tolerance in normal mice.

METHODS

We adoptively transferred into C57BL/6 mice a variety of syngeneic myeloid antigen-presenting cell populations exposed to different activation stimuli as well as to meals of necrotic and apoptotic cells. We studied expression of autoimmunity in the immunized mice by serologic evaluation of autoantibody production, subclass analysis of Ig production, clinical evidence of kidney disease, glomerular immune complex deposition, and renal pathology.

RESULTS

Injection of mice with DCs incubated with apoptotic or necrotic cells, as well as, surprisingly, with DCs cultured in media alone, induced high levels of IgG autoantibodies, including anti-double-stranded DNA (anti-dsDNA) antibodies. In striking contrast, transfer of equivalent-treated macrophages failed to generate IgG autoantibodies. IgG was deposited in the kidneys of mice vaccinated with DCs, but despite high levels of anti-dsDNA antibodies, these mice did not develop overt nephritis. Serologic evaluation of the antibody response revealed that the mice primarily developed elevated levels of IgG1 antibodies, including high levels of IgG1 anti-dsDNA.

CONCLUSION

The data suggest that mature myeloid DCs are able to break tolerance and induce lupus autoantibodies in normal hosts, but that other susceptibility factors must be in place to induce long-lasting autoimmunity and clinical expression of disease.

Bone marrow cells as an origin of immune-mediated hearing loss

The MRL/lpr mouse, which is homozygous for the recessive lpr genes and has a mutation in the Fas gene encoding a cell-surface receptor for apoptosis, exhibits severe lymphadenopathy and develops systemic lupus erythematosus (SLE)-like disease. It has recently been reported that this mouse also manifests sensorineural hearing loss (SHL) with cochlear pathology at 20 weeks of age. We examined the effects of reconstituting severe combined immunodeficient (SCID) mice with MRL/lpr bone marrow on the development of SHL. These mice normally develop neither SHL nor cochlear pathology. Immune-mediated SHL and cochlear pathology did, indeed, occur following transfer of MRL/lpr bone marrow into SCID mice. These findings suggest that the development of SHL and cochlear pathology observed in MRL/lpr mice and in SCID mice receiving MRL/lpr bone marrow are the result of bone marrow defects rather than the result of a problem intrinsic to the cochlea.

Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells

Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells The MRL/lpr mouse, which has a mutation in the Fas gene encoding a cell-surface receptor for apoptosis, shows an accumulation of abnormal immunocompetent cells and SLE-like disease. It has recently been reported that this mouse also manifests sensorineural hearing loss (SHL) with cochlear pathology at 20 weeks of age. We examined the effects of injecting MRL/lpr spleen cells on the development of SHL in severe combined immunodeficient (SCID) mice, which originally develop neither SHL nor cochlear pathology. Immune-mediated SHL and cochlear pathology were, indeed, transferred to the SCID mice by the injection of spleen cells from the MRL/lpr mice. These findings suggest that cell-mediated immunity is involved in the development of SHL and cochlear pathology.

Functional characterization of lymphoid cells generated in serum-deprived culture stimulated with stem cell factor and interleukin 7 from normal and autoimmune mice

We have investigated the phenotypic and functional characteristics of murine pre-B cells obtained in semisolid and liquid culture with stem cell factor (SCF) and interleukin 7 (IL-7). Both serum-supplemented and serum-deprived culture conditions were used. The source of bone marrow cells was either normal mice (CD1 and C3H) or the lupus strain of mice MRL/lpr and its congenic strain MRL/+. SCF (100 ng/ml) and IL-7 (250 ng/ml) supported murine B cell proliferation in vitro from all the murine strains analyzed both in serum-supplemented and serum-deprived conditions. Maximal colony growth was observed in both cases when the factors were used in combination. The growth factors alone induced some colony growth in serum-supplemented cultures but were either ineffective or had modest activity in serum-deprived cultures. Cells harvested from the colonies or generated in liquid cultures and stimulated with SCF + IL-7 in the absence of serum had almost exclusively a pre-B cell phenotype (BP-1+, B220+, slg-, CD4-, CD8-, Mac-1-, RB-6-). Both the maximal colony growth in semisolid culture and the maximal number of cells in liquid culture were observed at day 12-14. At this time, the pre-B cells failed to differentiate further and started to die. Pre-B cells generated in vitro were, however, capable of differentiating in vivo. SCID mice injected with 2 x 10(6) pre-B cells had readily detectable serum levels of IgM (54 +/- 26 micrograms/ml) and IgG (60 +/- 95 micrograms/ml) at 4 weeks and 6 weeks posttransplantation, respectively. Mature B and T cells of the donor major histocompatibility complex type were detected in the SCID mice at sacrifice 14 weeks posttransplantation. These data indicate that purified (> 80% BP-1+) populations of functional pre-B cells can be grown from murine bone marrow of normal mice as well as of lupus mice in serum-deprived cultures stimulated with SCF and IL-7. These cultures, therefore, provide a highly enriched source of pre-B cells but also contain T cell precursors that differentiate upon adoptive transfer into SCID mice.

Targeting of pancreatic islets of severe combined immunodeficient mice by passive transfer of allogeneic spleen cells from non-obese diabetic mice

The precise role of immune cells in beta cell killing and their manner of invasion of pancreatic islets in insulin-dependent diabetes mellitus (IDDM) are unclear. We have attempted to target pancreatic islets of severe-combined immunodeficient (SCID) mice with spleen cells from diabetic and non-diabetic female non-obese diabetic (NOD) mice given i.p. or i.v. Pancreatic, liver and kidney sections of SCID mice were assessed histologically for the presence of donor cells. The presence of raised levels of serum Ig was also used as an index of engraftment of donor cells in the periphery of SCID mice. All six SCID mice which received i.v. spleen cells from normal Swiss mice died within 2 weeks from graft versus host disease (GVHD) whereas five out of nine mice survived for 30 days after i.p. injection. No deaths were recorded after i.v. or i.p. injection of spleen cells from NOD mice. Pancreatic islets of four out of six SCID recipients of diabetic and three out of five recipients of non-diabetic spleen cells following i.p. injection showed lymphocytic infiltrates in the peri-islet and perivascular regions. All SCID mice which received i.v. spleen cells from diabetic (six SCID recipients) and non-diabetic NOD mice (seven SCID recipients) showed peri-islet and perivascular infiltrates in their pancreas. Immunohistochemical analysis showed that the islet engrafted cells were of CD4 and CD8 phenotype. Donor cells were also observed in the exocrine pancreas of some recipients. A majority of mice showed various degrees of lymphocytic aggregates in the perivascular regions of the liver but not in the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

CD4-8- T-cells increase in MRI/lpr mice treated with thymic factors

The in vivo effect of thymic factors on immature lymphocytes was analysed in MRL/lpr mice. This strain carries a genetic defect that causes during their life cycle a block of T-cell differentiation and abnormal proliferation of CD4-8- (double-negative, DN) T-lymphocytes. In vivo administration of four preparations of thymic factors, thymopentin (TP-1), thymopoietin (TP-5), thymolymphotropin (TLT), and thymomodulin (TMD) into young (2-month-old) MRL/lpr mice induced a significant increase of DN T-cells both in the thymus and in the peripheral lymph nodes, with a concomitant decrease of double-positive (DP) T-cells in the thymus and of single-positive (SP) T-cells in the lymph nodes. The level of DNA fragmentation measured as propidium iodide fluorescence was increased in the thymus population of young mice and in the lymph node population of old mice treated with TLT. SCID mice transplanted with lymph node cells from MRL/lpr donors (MRL-->SCID) developed graft versus host (GvH) reaction due to the activation of MRL CD8+ alloreactive T-cells. This model was used to analyse the effect of TMD/TLT in vivo on MRL cell proliferation and expansion; in fact, spleen cells from MRL-->SCID mice after treatment with TMD/TLT showed an increased cell proliferation, and an expansion of DN T-cells with a concomitant decrease of SP cells (both CD4+ and CD8+ cells). Decreased SP cell numbers in this context could explain why TMD/TLT treatment of SCID mice engrafted with MRL cells increased their survival compared to untreated MRL-->SCID mice.

Attenuation of lpr-graft-versus-host disease (GVHD) in MRL/lpr spleen cell-injected SCID mice by in vivo treatment with anti-V beta 8.1,2 monoclonal antibody

When MRL/lpr (H-2k) spleen cells were intraperitoneally injected into C.B-17-scid/scid (severe combined immunodeficient (SCID)) (H-2d) mice, the SCID (SCID-MRL/lpr) mice manifested a severe wasting syndrome with weight loss, splenic atrophy, and lymphoid cell infiltration in the liver and lung, as seen in lpr-GVHD. In contrast, MRL/+ spleen cell-injected SCID (SCID-MRL/+) mice did not show lpr-GVHD. The spleens of SCID-MRL/lpr mice showed progressive increases in donor CD4+ and CD8+ T cells from 4 to 12 weeks after injection and a decrease in B cells at 12 weeks. SCID-MRL/+ mice showed a stable engraftment of CD4+ and CD8+ T cells and a progressive increase in B cells. Analyses of T cell receptor (TCR) repertoires (V beta 6, V beta 8.1,2 and V beta 11) revealed that the V beta 8.1,2+ T cells were found more frequently in SCID-MRL/lpr mice than in SCID-MRL/+ mice. When SCID-MRL/lpr mice were treated with intraperitoneal injection of an anti-V beta 8.1,2 (KJ16) MoAb, V beta 8.1,2+ T cells were markedly depleted, and the severity of lpr-GVHD was attenuated at 4 and 8 weeks after treatment, in contrast to normal rat IgG-injected SCID-MRL/lpr mice. However, the KJ16 MoAb-treated SCID-MRL/lpr mice suffered from severe lpr-GVHD 12 weeks after treatment, although V beta 8.1,2+ T cells were still maintained at a low level. These findings suggest that V beta 8.1,2+ T cells are a major T cell population that mediates lpr-GVHD in the early stage of lpr-GVHD, but that in the later stage, the other T cell populations may proliferate naturally or in accordance with the depletion of V beta 8.1,2+ T cells, and contribute to the development of lpr-GVHD.

Autoimmunity versus allo- and xeno-reactivity in SCID mice

The ability of SCID mice to accept xenografts has been exploited to study the survival, function and potential of peripheral blood mononuclear cells (PBMC) from patients with autoimmune disorders to produce tissue injury in the mouse. Studies performed with PBMC obtained from patients with organ specific and multisystem autoimmune diseases indicate that human PBMC survive in SCID mice for several months, produce IgG and autoantibodies with the same specificities as are found in the donor. Tissue injury is not generally observed in the SCID mouse recipient. SCID mice have also been partially reconstituted with bone marrow from BB (diabetic) and MRL (lupus) mice. SCID mice injected with both spleen cells from mice with collagen induced arthritis together with native bovine collagen developed more severe arthritis than the donors. SCID mice have therefore proven to be a useful resource to study autoimmunity. In both xeno- and allografts of mature lymphocytes, graft versus host reactions occur. Further studies will be necessary to improve donor cell survival without aggravating graft versus host disease.

The Fas protein is expressed at high levels on CD4+CD8+ thymocytes and activated mature lymphocytes in normal mice but not in the lupus-prone strain, MRL lpr/lpr

The lymphoproliferation (lpr) mutation in the MRL strain of mice is caused by the insertion of the early transposable element ETn in the Fas gene. The insertion causes a striking decrease in Fas mRNA expression and is associated clinically with marked acceleration of the lupus-like disease. To further explore the role of the Fas protein in T-cell selection in the thymus and tolerance in the peripheral immune system, we produced a monospecific polyclonal anti-murine Fas antibody that binds to a polymorphic region of the protein. Fas protein expression was detected on approximately 90% of BALB/c and MRL +/+ thymocytes, and the expression was highest on CD4+CD8+ thymocytes, the stage at which most thymocytes die by apoptosis. In contrast to the high level of expression of Fas on thymocytes, Fas was detected on < 10% of normal splenic T cells. After activation of splenic T cells with Con A or anti-CD3 and interleukin 2, Fas expression increased approximately 10-fold. Fas expression on splenic B cells was also markedly up-regulated after activation with lipopolysaccharide or anti-mu antibodies. The Fas protein was not detected on resting or activated lymphocytes obtained from MRL lpr/lpr mice. Together, these findings suggest that Fas plays a role in both thymic selection and T-cell survival in the periphery and that the accelerated autoimmunity in MRL lpr/lpr mice results from a defect in both of these pathways.