MRL/1 and BXSB male mice have a systemic lupus erythematosus (SLE)-like disease similar to but more acute than that occurring in NZB X W mice. The common elements of lymphoid hyperplasia, B-cell hyperactivity, autoantibodies, circulating immune complex (IC), complement consumption, IC glomerulonephritis with gp70 deposition, and thymic atrophy were found in all three kinds of SLE mice. On the basis of these common elements, SLE seen in these mice can be considered a single disease in the same sense that human SLE is one disease. The differences in the SLE expressed in the different mice are no greater than those found in an unselected series of humans with SLE. However, the significant quantitative and qualitative variations in abnormal immunologic expression suggest that different constellations of factors, genetic and/or pathophysiologic, may operate in the three murine strains and that each constellation is capable of leading, via its particular abnormal immunologic consequences, to the activation of common immunopathologic effector mechanisms that cause quite similar SLE-like syndromes. From an experimental point of view, the availability of several inbred murine strains of commonplace histocompatibility types that express an SLE-like syndrome makes possible innumerable manipulations which should help to elucidate the nature and cause(s) of this disorder.

https://rupress.org/jem/article-pdf/148/5/1198/1089624/1198.pdf

Spontaneous murine lupus-like syndromes. Clinical and immunopathological manifestations in several strains.

Publisher Summary This chapter reviews the histopathologic, serologic, lymphocytic, virological, hormonal, and genetic characteristics of murine models of systemic lupus erythematosus (SLE). The pathogenetic mechanisms underlying murine SLE are highly complex, apparently well-programmed genetically, but still diverse and their bases not as yet well defined. Significant serologic and cellular experimental data support the statement that the final immunopathologic perturbation in murine (and human) SLE is a B lymphocyte hyperactivity with corresponding enhancement of serum antibodies and autoantibodies, particularly IgG, and consequent formation of pathogenic antigen–antibody ICs. On the basis of the available data, it appears that this B cell hyperactivity is polyclonal but not necessarily panclonal in nature, because not only antibodies against a wide array of autoantigens but also antibodies against incidental antigens, such as haptens, can be detected. The presence of autoantibodies and of their idiotypes in some recombinant lupus x normal murine lines expressing the normal partner's V genes, normal mice in which an exogenous or endogenous (Ipr gene) immunostimulator has been introduced, and unmanipulated normal mice indicate that lupus mice are not unique in their structural genetic Ig elements, whose presence determines the development of their autoimmune disease. The cause of B cell hyperactivity in lupus has not yet been fully elucidated. Autonomous B cell maturation does not appear likely, because B cell proliferation and differentiation in lupus mice was found to be dependent on the same number of accessory signals as in normal mice.

Murine models of systemic lupus erythematosus.

Immune reactivity is greater in females than in males. In both experimental animals and in man there is a greater preponderance of autoimmune diseases in females, compared with males. Studies in many experimental models have established that the underlying basis for this sex-related susceptibility is the marked effects of sex hormones. Sex hormones influence the onset and severity of immune-mediated pathologic conditions by modulating lymphocytes at all stages of life, prenatal, prepubertal, and postpubertal. However, despite extensive studies, the mechanisms of sex hormone action are not precisely understood. Earlier evidence suggested that the sex hormones acted via the thymus gland. In recent years it has become apparent that sex hormones can also influence the immune system by acting on several nonclassic target sites such as the immune system itself (nonthymic lymphoid organs), the central nervous system, the macrophage-macrocyte system, and the skeletal system. Immunoregulatory T cells appear to be most sensitive to sex hormone action among lymphoid cells. Several mechanisms of action of sex hormones are discussed in this review. The possibility of using sex hormone modulation of immune responses for the treatment of autoimmune disorders is a promising area for future investigation.

Sex hormones, immune responses, and autoimmune diseases. Mechanisms of sex hormone action

Whether B-1a (CD5+) cells are a distinct lineage derived from committed fetal/neonatal precursors or arise from follicular B-2 cells in response to BCR ligation and other, unknown signals remains controversial. Recent evidence indicates that B-1a cells can derive from adult precursors expressing an appropriate specificity when the (self-) antigen is present. Antibody specificity determines whether a B cell expressing immunoglobulin transgenes has a B-2, B-1a or marginal zone (MZ) phenotype. MZ cells share many phenotypic characteristics of B-1 cells and, like them, appear to develop in response to T independent type 2 antigens. Because fetal-derived B cell progenitors fail to express terminal deoxynucleotidyl transferase (TdT) and for other reasons, they are likely to express a repertoire that allows selection into the B-1a population. As it is selected by self-antigen, the B-1 repertoire tends to be autoreactive. This potentially dangerous repertoire is also useful, as B-1 cells are essential for resistance to several pathogens and they play an important role in mucosal immunity. The CD5 molecule can function as a negative regulator of BCR signaling that may help prevent inappropriate activation of autoreactive B-1a cells.

Origins and functions of B-1 cells with notes on the role of CD5.

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.

/pdf/effect-of-castration-and-sex-hormone-treatment-on-survival-56shoxf5nq.pdf

Effect of castration and sex hormone treatment on survival, anti-nucleic acid antibodies, and glomerulonephritis in nzb/nzw f1 mice.

Publisher Summary This chapter discusses the New Zealand Black (NZB) strain of mice that has attracted the attention of investigators throughout the world as an experimental model for human connective tissue disease. The mice developed an autoimmune type of hemolytic anemia with autoantibody production, and they were the first documented strain of experimental animals to develop autoimmune disease spontaneously. The autoimmune phenomena of the NZB strain appeared in all F 1 hybrids. In some of the hybrid strains, the autoimmune disorder maintained the NZB characteristic of erythrocyte autoantibody production. But in certain others, the nature of the process changed to one of antinuclear antibody production and renal disease in a form closely resembling lupus nephritis. The chapter describes the patterns of development of the disease processes in the two groups of mice. The NZB X NZW hybrid strain with its hybrid vigor, its clear-cut laboratory markers, and its accurately predictable pattern of disease, is a much more satisfactory model. The two groups of animals represent two rather different types of autoimmune disorder. Disorders could be transmitted by isogenic grafts of immunologically competent cells from the spleen, thus identifying such cells as the executive clones responsible for autoantibody production.

B J Helyer

Papers

The immunology and pathology of nzb mice.