Inhibition of association vs. dissociation of high-avidity DNA/Anti-DNA Conplexes: Possible involvement of secondary hydrogen bonds

Recent results on the conditions of ionic strength needed to prevent the association of dsDNA with high avidity human anti-dsDNA, were compared with the insufficiency of even the highest practicable ionic strengths to effect the dissociation of such antigen-antibody complexes, once formed (1). Further analysis of these results make us conclude that such high avidity dsDNA-anti-dsDNA complexes. which in the initial stages of their formation are mainly of the Coulombic variety. subsequently evolve, at least in part, into hydrogen bonds.     

Dissociation studies of DNA/anti-DNA complexes in relation to anti-DNA avidity

Antibodies to dsDNA differ in their avidity towards the antigen. The electrostatic interaction between DNA and anti-DNA is sensitive to increases in pH and/or ionic strength and therefore, elution studies employing either of these permit discrimination between anti-dsDNA populations that differ in avidity. Another way to determine anti-dsDNA avidity is the calculation of Farr/PEG ratios. These are obtained by division of the amount of anti-DNA measured with the Farr assay (which does not detect low avidity anti-dsDNA) by the amount measured with the PEG assay (which does detect low avidity anti-dsDNA). With these separate approaches, we compared the sera of 17 SLE patients with nephritis with the sera of 17 patients with central nervous system (CNS) involvement. Farr/PEG ratios and sensitivity to high pH elution of anti-dsDNA in the sera of these patients both permitted discrimination between the two groups of patients. The anti-dsDNA of patients with nephritis was found to have a significantly higher avidity towards DNA than anti-dsDNA of patients with cerebral disease. We also observed a significant correlation between Farr/PEG ratios and the salt lability of anti-dsDNA.     

Transforming growth factor-beta trans-modulates the expression of colony stimulating factor receptors on murine hematopoietic progenitor cell lines

Transforming growth factor beta (TGF-beta) is a potent and selective growth inhibitor of early hematopoietic progenitors and leukemic cells. The cellular mechanism(s) underlying this antiproliferative effect is, however, currently unknown. In the present study, we demonstrate that TGF-beta inhibits the expression of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL-3), and granulocyte-CSF (G-CSF) receptors on murine factor-dependent and independent hematopoietic progenitor cell lines without a significant change in receptor affinity. A maximum reduction in GM-CSF receptor numbers of 65% to 77% was observed by 96-hour incubation with TGF-beta. The TGF- beta induced trans-down-modulation of GM-CSF receptors was prolonged, noncytotoxic but reversible, and not due to endogenous production of GM- CSF. The TGF-beta induced reduction in CSF receptor numbers preceded TGF-beta's growth inhibitory action. In addition, the ED50 (1 to 10 pmol/L) for TGF-beta's CSF receptor modulatory and antiproliferative effect was similar. The effect of TGF-beta on cell surface CSF receptor expression was specific, because the expression of other cell surface proteins (Ly 5 and Ly 17) was not affected by TGF-beta treatment, and because other growth inhibitors (tumor necrosis factor and interferon) did not affect CSF receptor expression. These data suggest that the downregulation of the growth of hematopoietic progenitor cells by TGF- beta involves reducing the cell surface expression on growth factor receptors.     

Factors that affect human hemopoiesis are produced by T-cell growth factor dependent and independent cultured T-cell leukemia-lymphoma cells

Some laboratory results and clinical situations suggest that human T cells may be important in the regulation of growth of hematopoietic cells. Since the discovery of T-cell growth factor (TCGF), systems are now available for the long-term specific in vitro propagation of mature normal or neoplastic human T cells, providing an opportunity to study the influence of T cells on hematopoiesis. Recently, 24 cell lines from patients with cutaneous T-cell lymphoma (CTCL) and T-cell acute lymphoblastic leukemia (T-ALL) were grown with TCGF and then assessed for release of humoral factors that affect hematopoiesis. Conditioned media (CM) from these cell lines were tested for erythroid burst- promoting activity (BPA) and granulocyte colony-stimulating activity (CSA). BPA was detected in CM from 3/6 cultures of T-ALL patients and 4/6 CTCL cultures. CSA was found in the CM from 6/8 cultures of T-ALL patients, 7/12 CTCL cultures, and 3/4 CTCL cell lines that become independent of exogenous TCGF for growth. The CSA from several of the neoplastic T-cell cultures stimulated high levels of eosinophil colonies, a possible source of the eosinophilia seen in these patients. The ability of continuously proliferating human T lymphocytes, which retain functional specificity and responsiveness to normal humoral regulation, to produce factors that directly or indirectly stimulate myeloid and erythroid colony formation lends further credence to the role of T lymphocytes in regulating hematopoiesis.     

Evaluation of erythropoiesis in long-term hamster bone marrow suspension cultures: absence of a requirement for adherent monolayer cells

In long-term hamster bone marrow cultures, proliferation and differentiation of hemopoietic stem cells occurs for several months without need for hydrocortisone or adherent stromal elements, which are requirements for bone marrow growth in all other species studied. Only the most primitive erythroid progenitors (BFU-E) are produced in the cultures. Following treatment of the cells with erythropoietin, these progenitor cells undergo differentiation into mature hemoglobinized red blood cells. Concomitant addition of erythropoietin (Epo) and prostaglandin-E1 (PGE1) results in the production of large numbers of maturing red blood cells. In cultures stimulated with Epo and PGE1, as many as 70% of the cells are benzidine-positive, while Epo alone stimulated as many as 45% of the cells to become erythroid. Epo and PGE1 do not have any apparent deleterious effect on the continuous hemopoiesis occurring in these cultures. Under identical conditions, syngeneic adherent cell cultures do not produce any erythroid elements. The development of mature red blood cells from primitive erythroid precursors occurs in the presence of Epo alone and without any apparent need for adherent stromal elements. These cultures provide a useful in vitro model for dissecting the positive and negative signals that regulate erythropoiesis.     

Low avidity antibodies to dsDNA as a diagnostic tool.

An evaluation of the diagnostic value of low avidity antibodies to double stranded DNA (dsDNA) measured by the polyethylene glycol (PEG) assay was undertaken. By routine screening low avidity anti-dsDNA were detected in the serum samples of 106 hitherto unknown patients. Clinical data of these patients were collected and when only low avidity anti-dsDNA was present (n = 92) a varied disease spectrum was observed. A diagnosis of systemic lupus erythematosus (SLE) was established in 48/92 (52%), lupus-like disease in 21/92 (23%), autoimmune hepatitis in 9/92 (10%), rheumatoid arthritis in 8/92 (9%), and mixed connective tissue disease in 2/92 (2%) of all patients. Patients with definite SLE were all older than 45 years and predominantly female (46/48, 96%). They showed a remarkably low incidence of renal disease (2/69, 3%). When high avidity antibodies to dsDNA as measured by the Farr assay were present as well (n = 14) a diagnosis of SLE could be established in 12/14 (86%) of all patients, indicating the secondary importance of low avidity anti-dsDNA in these patients.     

Changes in clinical features of patients with systemic lupus erythematosus followed prospectively over 2 decades

Summary In the past decades the general concept of the disease course and the prognosis of systemic lupus erythematosus (SLE) has changed dramatically. The improvement in prognosis of our SLE patients is often said to be related to the growing awareness of the disease. This study focussed on whether or not the clinical features at the onset of the disease, and at diagnosis, and the clinical course as well as the age at the onset of the disease had changed during the past decades. No obvious differences were observed in the age at the onset of the disease or in the age at diagnosis. Of the 22 clinical signs studied, only the prevalence of Raynaud's phenomenon at the onset of the disease had increased during the past 20 years. At diagnosis, the prevalence of oral ulcers and false positive syphilis test had decreased. Only small differences in the type but not in the number of exacerbations were observed; in the past 20 years, the prevalence of renal involvement increased from 20% to 43%. However, this was not significant. Our results did not support the theory that during the past 2 decades the disease had changed in its expression, neither did we find that the disease is presently diagnosed at an earlier age, as would be expected from the increased awareness of the disease.