Microparticles as antigenic targets of antibodies to DNA and nucleosomes in systemic lupus erythematosus.

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by antibodies to DNA and other nuclear molecules. While these antibodies can form immune complexes, the mechanisms generating the bound nuclear antigens are not known. These studies investigated whether microparticles can form complexes with anti-DNA and other anti-nucleosomal antibodies. Microparticles are small membrane-bound vesicles released from dead and dying cells; these particles contain a variety of cellular components, including DNA. To assess antigenicity, microparticles generated in vitro from apoptotic cell lines were tested using murine monoclonal anti-DNA and anti-nucleosomal antibodies as well as plasma from lupus patients. Antibody binding was assessed by flow cytometry. As these studies showed, some but not all of the monoclonal antibodies bound to microparticles prepared from apoptotic HL-60, THP-1 and Jurkat cells. For HL-60 cells, both staurosporine and UV radiation led to the production of antigenically active particles. For the anti-DNA antibody with high particle binding, prior treatment of DNase reduced activity. With plasma from patients with SLE, antibody binding to microparticles was present although a clear relationship with anti-DNA antibody levels was not observed. To determine whether lupus plasma contains immune complexes with particle properties, particle preparations were tested for bound IgG by flow cytometry. These studies indicated that lupus plasma contains particles with IgG binding, with numbers correlated with anti-DNA levels. Together, these findings indicate that microparticles display DNA and nucleosomal molecules in an antigenic form and could represent a source of immune complexes in SLE.

Genetic bases of estrogen-induced tumorigenesis in the rat: mapping of loci controlling susceptibility to mammary cancer in a Brown Norway x ACI intercross.

Exposure to estrogens is associated with an increased risk of breast cancer. Our laboratory has shown that the ACI rat is uniquely susceptible to 17beta-estradiol (E2)-induced mammary cancer. We previously mapped two loci, Emca1 and Emca2 (estrogen-induced mammary cancer), that act independently to determine susceptibility to E2-induced mammary cancer in crosses between the susceptible ACI rat strain and the genetically related, but resistant, Copenhagen (COP) rat strain. In this study, we evaluate susceptibility to E2-induced mammary cancer in a cross between the ACI strain and the unrelated Brown Norway (BN) rat strain. Whereas nearly 100% of the ACI rats developed mammary cancer when treated continuously with E2, BN rats did not develop palpable mammary cancer during the 196-day course of E2 treatment. Susceptibility to E2-induced mammary cancer segregated as a dominant or incompletely dominant trait in a cross between BN females and ACI males. In a population of 251 female (BN x ACI)F(2) rats, we observed evidence for a total of five genetic determinants of susceptibility. Two loci, Emca4 and Emca5, were identified when mammary cancer status at sacrifice was evaluated as the phenotype, and three additional loci, Emca6, Emca7, and Emca8, were identified when mammary cancer number was evaluated as the phenotype. A total of three genetic interactions were identified. These data indicate that susceptibility to E2-induced mammary cancer in the BN x ACI cross behaves as a complex trait controlled by at least five loci and multiple gene-gene interactions.

Genetic determination of susceptibility to estrogen-induced mammary cancer in the ACI rat: mapping of Emca1 and Emca2 to chromosomes 5 and 18.

Hormonal, genetic, and environmental factors play major roles in the complex etiology of breast cancer. When treated continuously with 17beta-estradiol (E2), the ACI rat exhibits a genetically conferred propensity to develop mammary cancer. The susceptibility of the ACI rat to E2-induced mammary cancer appears to segregate as an incompletely dominant trait in crosses to the resistant Copenhagen (COP) strain. In both (ACI x COP)F(2) and (COP x ACI)F(2) populations, we find strong evidence for a major genetic determinant of susceptibility to E2-induced mammary cancer on distal rat chromosome 5. Our data are most consistent with a model in which the ACI allele of this locus, termed Emca1 (estrogen-induced mammary cancer 1), acts in an incompletely dominant manner to increase both tumor incidence and tumor multiplicity as well as to reduce tumor latency in these populations. We also find evidence suggestive of a second locus, Emca2, on chromosome 18 in the (ACI x COP)F(2) population. The ACI allele of Emca2 acts in a dominant manner to increase incidence and decrease latency. Together, Emca1 and Emca2 act independently to modify susceptibility to E2-induced mammary cancer.

Genetic bases of renal agenesis in the ACI rat: mapping of Renag1 to chromosome 14.

Unilateral renal agenesis (URA) is a common developmental defect in humans, occurring at a frequency of approximately 1 in 500-1,000 births. Several genetic syndromes include bilateral or unilateral renal agenesis as an associated phenotype. However, URA frequently occurs in individuals not afflicted by these syndromes and is often asymptomatic. Although it is clear that genetic factors contribute to the etiology of URA, the genetic bases of URA are poorly defined at this time. ACI rats, both males and females, exhibit URA at an incidence of 5%-15%. In this article we characterize the incidence of URA in female and male F(1), F(2), and backcross (BC) progeny from reciprocal genetic crosses between the ACI strain and the unaffected Brown Norway (BN) strain. Through interval mapping analyses of 353 phenotypically defined female F(2) progeny, we mapped to rat Chromosome 14 (RNO14) a genetic locus, designated Renag1 (Renal agenesis 1), that serves as the major determinant of URA in these crosses. Further genotypic analyses of URA-affected female and male F(2) and BC progeny localized Renag1 to a 14.4-Mb interval on RNO14 bounded by markers D14Rat50 and D14Rat12. The data from these genetic studies suggest that the ACI allele of Renag1 acts in an incompletely dominant and incompletely penetrant manner to confer URA.

Genetic mapping of Eutr1, a locus controlling E2-induced pyometritis in the Brown Norway rat, to RNO5.

In certain rat strains, chronic estrogen administration can lead to pyometritis, an inflammation of the uterus accompanied by infection and the accumulation of intraluminal pus. In this article, we report that the Brown Norway (BN) rat is highly susceptible to pyometritis induced by 17beta-estradiol (E2). The susceptibility of the BN rat to E2-induced pyometritis appears to segregate as a recessive trait in crosses to the resistant August x Copenhagen Irish (ACI) strain. In a (BN x ACI)F(2) population, we find strong evidence for a major genetic determinant of susceptibility to E2-induced pyometritis on rat chromosome 5 (RNO5). Our data are most consistent with a model in which the BN allele of this locus, designated Eutr1 (Estrogen-induced uterine response 1), acts in an incompletely dominant manner to control E2-induced pyometritis. Furthermore, we have confirmed the contribution of Eutr1 to E2-induced uterine pyometritis using an RNO5 congenic rat strain. In addition to Eutr1, we obtained evidence suggestive of linkage for five additional loci on RNO2, 4, 11, 17, and X that control susceptibility to E2-induced pyometritis in the (BN x ACI)F(2) population.