Development of murine lupus in CD4-depleted NZB/NZW mice. Sustained inhibition of residual CD4+ T cells is required to suppress autoimmunity.

Chronic administration of anti-CD4 mAb prevents autoimmune disease in NZB/NZW F1 (B/W) mice. This may be due either to CD4 cell depletion or to inhibition of CD4 cell function. To evaluate the relative importance of these mechanisms, we devised a system in which the consequences of cell depletion could be analyzed independent of the inhibitory effects of chronic mAb therapy. This was accomplished by performing adult thymectomy before mAb administration. Specifically, female B/W mice underwent thymectomy or sham thymectomy at age 6 wk, followed at age 3 mo by a short course of either anti-CD4 (2 mg/wk for 3 wk) or saline. Treatment with anti-CD4 depleted 90% of circulating CD4 cells, but a small subpopulation (10%) of CD4 cells was refractory to depletion. In non-thymectomized mice, the CD4 population gradually reconstituted after cessation of therapy. In contrast, in thymectomized mice, recovery of CD4 cells was prevented by the absence of the thymus. Despite the striking reduction in CD4 cells in thymectomized mice, severe autoimmune disease developed, with autoantibody levels, proteinuria, and mortality comparable with non-thymectomized, nondepleted controls. The unexpected development of lupus nephritis in thymectomized, CD4-depleted B/W mice suggested that the thymus might be required to achieve the benefits of therapy with anti-CD4. To exclude this possibility, we demonstrated that chronic therapy with anti-CD4 prevents autoimmunity in thymectomized B/W mice. These findings imply that: 1) substantial depletion of CD4 T cells is not sufficient to suppress autoimmunity; 2) suppression of autoimmunity requires sustained functional inhibition of CD4 T cells; and 3) a small subpopulation of CD4 cells that is refractory to depletion by anti-CD4 is sufficient to promote the full expression of murine lupus in B/W mice.

Regulation of autoimmunity and donor cell engraftment by recipient Lyt-2+ cells during the graft-versus-host reaction.

When lymphocytes from DBA/2 mice are transferred to (C57BL X DBA/2)F1 (BDF1) mice, the ensuing graft-vs.-host reaction (GVHR) causes an autoimmune illness resembling human SLE. To examine the role of recipient T cells in this process, BDF1 mice were depleted of L3T4+ or Lyt-2+ cells by thymectomy followed by treatment with mAbs to L3T4 or Lyt-2. This produced sustained depletion of these T cell subsets. Subsequent grafting with parental DBA/2 lymphocytes produced autoimmune disease in mice depleted of L3T4+ cells and controls but not in mice depleted of Lyt-2+ cells. Analysis of blood lymphocytes 4 wk after donor cell transfer demonstrated that BDF1 recipients depleted of Lyt-2+ cells were virtually repopulated with donor T lymphocytes, compared with less than or equal to 35% donor cell engraftment in all other groups. Thus, recipient Lyt-2+ cells influence both host cell engraftment and autoimmunity during the parent-into-F1 GVHR.

Effect of androgen therapy on survival and suppressor cell activity in aged NZB/NZW F1 hybrid mice.

Male NZB/NZW F1 hybrid (B/W) mice survive their first year of life and die of lupus nephritis or lymphoid malignancy during the second year. Androgen therapy, even if delayed until 9 months of age, improves survival considerably. We report here that androgen therapy in aged B/W mice is associated with improved cell-mediated immune function as well as increased survival. Androgen treated mice have significantly augmented spleen cell responses to phytohaemagglutinin (PHA) and a decreased incidence of abnormal splenic suppressor activity. These results suggest that androgen may prolong survival in B/W mice in part through an effect on abnormally suppressive regulatory cells that impair T lymphocyte function.

Thymic influences on autoimmunity in MRL-lpr mice.

We have examined the role of the thymus in the development of autoimmunity in MRL/Mp-lpr/lpr (MRL-lpr) mice. MRL-lpr mice develop a lymphoproliferative disorder characterized by features of systemic lupus erythematosus and by massive proliferation of a subpopulation of Lyt-1+23- T cells. Using fluorescein-conjugated monoclonal antibodies and the fluorescence-activated cell sorter, we have found an abnormal pattern of differentiation within the MRL-lpr thymus characterized by a loss of Lyt-123+ thymocytes and an increased frequency of Lyt-1+23- thymocytes. Neonatal thymectomy retarded lymphoproliferation, reduced autoantibody concentrations, improved renal function, and prolonged life. Furthermore, neonatal thymectomy resulted in a relatively specific elimination of the subset of T cells involved in the lymphoproliferative process. These findings suggest that thymic maturation of T cells with alloantigenic characteristics of a helper subpopulation may contribute to the marked lymphoproliferation and severe autoimmunity of MRL-lpr mice. Neonatal thymectomy may protect against autoimmunity by preventing the maturation of this helper subpopulation.

Clearance of sensitized erythrocytes in NZB/NZW mice. Effects of castration and sex hormone treatment.

The clearance of particulate immune complexes consisting of erythrocytes sensitized with IgG or complement was investigated in (NZB x NZW)F1 (B/W) mice. Treatment of castrated B/W mice with androgen or estrogen was able to modulate this clearance. Young (3-month-old) male and female B/W mice cleared IgG-sensitized mouse erythrocytes rapidly, whereas older males (13 months) and females (7 months) showed a marked impairment in their ability to clear these cells. In addition, erythrocytes sensitized with complement in the absence of antibody were cleared within 5 min in young B/W mice. Older mice showed a greater and more rapid clearance rate of these cells. Castrated female B/W mice treated with androgen implants from three weeks of age showed improved clearance of IgG-sensitized erythrocytes at 7 months, whereas estrogen-treated male mice showed delayed clearance. These results suggest an age-dependent defect in the clearance of IgG-sensitized particles, perhaps due to diminished levels of serum complement and/or saturation of Fc receptors. In addition, there is an alteration in the clearance of complement-sensitized erythrocytes which may be related to changes in macrophage activity or enzyme inactivators of C3 and C4. The possible mechanisms responsible for the hormonal modulation of clearance are discussed in relation to the known ability of these hormones to influence autoimmune diseases.

Quantitative immunofluorescence microscopy of renal glomeruli from mice exhibiting murine lupus erythematosus.

Pathologic changes in renal glomeruli of mice with systemic murine lupus erythematosus were quantified using microfluorophotometry. Cryostat sections were taken from kidneys of affected mice, stained with fluorescein-conjugated anti-mouse immunoglobulin, and the extent of immune complex glomerulonephritis was determined. A subjective microscopic examination procedure, which has been used previously, was compared with quantitative microfluorophotometry and a close correlation between the results using each of the two methods was found. Since the microfluorometric procedure measures the total fluorescence per glomerulus, subjective microscopy must estimate that same quantity in a linear fashion. The present advance in measuring capability indicates good potential for rapid, quantitative measurements for further studies on systemic lupus erythematosus, and on other tissue sections stained with fluorescent antibodies.

Short gastric veins as the major portal of entry for milk-borne murine mammary tumor virus.

The flow pattern of the short gastric veins that drain the fundic portion of the stomach appeared to influence mammary tumorigenesis. In I and C57BL mice, strains that are highly resistant to murine mammary tumor virus (MuMTV)-induced mammary tumorigenesis, the short gastric veins empty directly into the splenic vein outside the spleen, connecting with the portal system. In (C57BL X I)F1 mice, which are highly susceptible to MuMTV-induced mammary tumorigenesis, the short gastric veins empty directly into the superior hilus of the spleen, connecting with the splenic parenchyma. Neonatal splenectomy or cauterization of the short gastric veins of (C57BL X I)F1 mice prior to the introduction of MuMTV by foster-nursing delayed the onset and reduced the final incidence of mammary tumors. When neonatal splenectomy was performed after milk-borne MuMTV introduction, it caused premature appearance of mammary tumors without affecting the final tumor incidence. In A, BALB/c, C3H, DBA/2, GR, and RIII mice, strains that are susceptible to MuMTV-induced mammary tumorigenesis, the short gastric veins also empty into the superior hilus of the spleen. Our findings suggest that susceptibility to mammary taumorigenesis may depend on the direct entry of milk-borne MuMTV into the splenic environment through the short gastric veins that drain the fundus of the stomach.

Delayed androgen treatment prolongs survival in murine lupus.

Female NZB/NZW F1 mice were treated as adults with 5-alpha-dihydrotestosterone powder packed into subcutaneous implants. Two treatment protocols were followed: (a) 3-mo-old mice received 6 mg of androgen, and (b) 6-mo-old mice were castrated and given 12 mg of androgen. Sham females received empty implants. Mice were followed monthly for surival, for antibodies to DNA and polyadenylic acid, and for renal histopathology. The percent survival at 11 mo was 74% for mice treated at 3 mo, compared to 11% for the sham controls, and 100% for mice treated at 6 mo, compared to 20% for their sham controls. Androgen-treated mice had less immune complex glomerulonephritis as determined by immunofluorescent and electron microscopy. Surprisingly, treated mice had no significant sustained reduction in antibodies to DNA although they had reduced antibodies to polyadenylic acid. These results suggest that androgens can still prolong survival and reduce immune complex deposition even when treatment is delayed to an age when disease is relatively established. After delayed androgen treatment, mice survive despite the presence of high levels of IgG antibodies to DNA.

beta-Estradiol reduces natural killer cells in mice.

beta-estradiol was administered to mice continuously by diffusion from a silastic tube that was implanted subcutaneously at 4 weeks of age. Four to 6 weeks of estrogen administration caused a substantial reduction in natural killer cell activity in the spleens from mice of either sex. Androgen (5alpha-dihydrotestosterone) did not. Castration of male or female mice did not affect natural killing and did not alter the effect of beta-estradiol. Estradiol did not affect natural killing in vitro and the loss of natural killing was not due to a soluble or a cellular suppressor of natural killing. The effects of estradiol were not dependent on the thymus, since estradiol reduced natural killing in mice that had been neonatally thymectomized. After removal of the estrogen implant, natural killing recovered over a period of 8 weeks. The loss of natural killing may reflect a loss of bone marrow secondary to estrogen-induced osteosclerosis.

Lipopolysaccharide induction of IgM antibodies to polyadenylic acid in normal mice.

Lipopolysaccharide (LPS) is able to induce autoantibodies reversibly in normal mice. Single or multiple doses of LPS induced a rapid and dose-dependent rise in antibodies to Poly A from 113 ng to 590 ng/ml serum as determined by Millipore filter radioimmunoassay. The response peaked at day 3 and was over by day 21. No response was seen if the LPS was chemically inactivated or injected into genetically nonresponsive mice. Antibodies were specific for Poly A and were not induced by T cell mitogens. Sucrose gradient ultracentrifugation demonstrated only IgM antibody. Neonatal thymectomy altered neither the immunoglobulin class nor quantity of antibody. Neonatal splenectomy did not affect antibody class but reduced the amount produced. No free Poly A could be detected in circulation after LPS stimulation. These findings suggest that normal mice have B lymphocytes capable of limited and reversible autoantibody production.

Effect of castration and sex hormone treatment on survival, anti-nucleic acid antibodies, and glomerulonephritis in NZB/NZW F1 mice.

NZB/NZW F1 mice of both sexes were castrated at 2 wk of age and implanted subcutaneously with silastic tubes containing either 5-alpha-dihydrotestosterone or estradiol-17-beta. Mice receiving androgen showed improved survival, reduced anti-nucleic acid antibodies, or less evidence of glomerulonephritis as determined by light, immunofluorescent, and electron microscopy. By contrast, opposite effects were observed in castrated mice receiving estrogen. Intact male NZB/NZW F1 mice received androgen implants at 8 mo, an age when they develop an accelerated autoimmune disease associated with a decline in serum testosterone concentration. Such treated mice had improved survival and reduced concentrations of antibodies to DNA and to polyadenylic acid (Poly A). Prepubertal castration of male NZB/NZW F1 mice results in an earlier appearance of IgG antibodies to Poly A. This effect of castration was prevented if neonatal thymectomy was also performed.

Androgenic hormones modulate autoantibody responses and improve survival in murine lupus.

Antibodies to native DNA and to polyadenylic acid (Poly A) occur spontaneously and undergo a regulated switch from IgM to IgG during the course of autoimmune disease in NZB/NZW F(1) (B/W) mice. B/W females have higher titers and earlier commitment to 7S antibodies to DNA and Poly A, whereas B/W males bind DNA and Poly A primarily by 19S antibodies. We have performed castration experiments to determine the effects of sex hormones on this switch from IgM to IgG.NZB/NZW F(1) (B/W) mice were either castrated or subjected to sham surgery at 2 wk of age and studied for immunoglobulin class of antibodies to nucleic acids at 4, 6, and 7 mo post-surgery. Prepubertal castration of males caused premature death in 60% of mice. Castrated males had a significant decline in their serum testosterone concentration, an increase in DNA and Poly A binding, and an accelerated switch from 19S to 7S antibodies to nucleic acids. Castrated females had no change in mortality. However, castrated females given maintained androgen treatment had a decreased mortality compared to castrated females receiving estrogen (14 vs. 94%). The anticipated switch to 7S antibodies to Poly A was almost eliminated in castrated females. These results suggest that sex hormones modulate immunologic regulation and that androgenic hormones are protective in murine lupus.

Effects of neonatal thymectomy and splenectomy on survival and regulation of autoantibody formation in NZB/NZW F1 mice.

NZW F1 (B/W) mice were subjected to sham surgery or neonatal thymectomy and/or splenectomy and studied for immunoglobulin class of antibodies to double-stranded DNA and polyadenylic acid (Poly A) at 4 to 13 months of age. These antibodies occur spontaneously during the course of autoimmune disease in B/W mice. Sera were fractionated by sucrose density gradient ultracentrifugation and assayed for antibodies by a filter radioimmunoassay method. IgM was recovered in the 19S region and IgG in the 7S region as demonstrated by immunodiffusion. In sham-operated controls, at all ages studied, anti-DNA antibodies were both IgM and IgG, with the former predominating in males, and the latter in females. In both sexes, anti-Poly A antibodies were primarily IgM in young mice. There was a sequential switch from IgM to either enhanced or new IgG production in the following sequence: female anti-DNA and anti-Poly A (6 months), male anti-DNA (9 months), and male anti-Poly A (11 months). Both thymectomy and splenectomy caused earlier death in male mice, whereas females lived significantly longer after thymectomy. Neonatal thymectomy in males caused a premature switch from IgM to IgG antibodies to DNA, but it had a transient effect in females. Thymectomy almost completely prevented the late switch to IgG antibodies to Poly A in both sexes. By contrast, splenectomy promoted the formation of IgG antibodies to Poly A in male mice. These results suggest that the newborn B/W thymus and spleen contain regulatory cells and/or factors exerting different controlling influences on spontaneous antibodies to DNA and Poly A. Male B/W mice appear to be under the regulatory influence of suppressor cells, whereas the predominant regulation in female B/W mice appears to be a helper effect.

Inhibition of mammary tumors by incomplete T-cell depletion.

The effects of neonatal and perinatal thymectomy on mammary tumorigenesis in (C57BL X I)F1fC3H hybrid female mice were determined. When hybrid females were neonatally thymectomized by controlled suction, a procedure that removes thymic lobes completely, a large proportion of animals developed stigmas of a fulminant wasting disease and died before tumors developed. However, when hybrid females were subjected to neonatal thymectomy by continuous suction, a procedure that resulted in retention of thymic remnants, they survived and manifested a significant prolongation of latent period before tumorigenesis. When complete removal of the thymus was carried out in the perinatal period, the effect on mammary tumorigenesis was critically dependent on the age at surgery. The procedure was without effect when performed at 1, 3, and 8 weeks of age. However, when it was performed at 9-12 days of age, there was a delay or a decrease in the appearance of mammary tumors. The extent of T-cell depletion and/or its timing in relationship to the introduction of murine mammary tumor virus appeared to play a critical role in determining the effect on eventual tumor development.

Stimulation of immune mechanisms against mammary tumors by incomplete T cell depletion.

When BALB/cfC3H females are subjected to continous suction thymectomy, a procedure that results in retention of thymic remnants, the latent period before tumor development is significantly prolonged. However, when BALB/cfC3H females are thymectomized by control suction, a procedure which removes thymic lobes completely, there is no effect on mammary tumorigenesis. Our results show that incomplete T cell depletion causes premature onset of non-T cell cytotoxicity, an augmentation of T cell cytotoxicity, and an alteration in a serum-blocking activity to mammary tumor target cells as tested in microcytotoxicity assay. On the other hand, complete neonatal thymectomy effectively and completely abrogates immune response to mammary tumor target cells. The inability of completely thymectomized mice to generate an immune response to MTV suggests (but does not prove) that MTV-induced mammary tumor target cell surface antigens are thymus-dependent.