Pj Hoedemaeker

EXPERIMENTAL GLOMERULONEPHRITIS IN RAT INDUCED BY ANTIBODIES DIRECTED AGAINST TUBULAR ANTIGENS .3. INVITRO EVALUATION OF CELL-MEDIATED IMMUNE-RESPONSES AGAINST IMMUNE-COMPLEXES INFLUENCED BY IMMUNOSUPPRESSIVE THERAPY

In this paper, cell-mediated immunity (CMI) as evaluated by in vitro migration inhibition assays an in vivo delayed type skin reactions in experimental immune complex glomerulonephritis (ECGN) was studied as well as the effect of treatment with immunosuppressive drugs on these immune responses. In glomerulonephritic rats MIF production as well as delayed type skin reactions could be demonstrated directed against tubular brushborder antigen (Fx1A) containing immune complexes or to their constituents (FX1A or rabbit IgG). Treatment of the animals with immunosuppressive drugs during settled disease state (autologous phase) abolished these cellular immune reactions. However, neither the glomerular depositions of rat IgG associated with the autologous phase, nor the urinary excretion was influenced. When treatment of the animals was started simultaneously with the induction of the ECGN both cellular and humoral immune responses as well as proteinuria were affected. It was concluded that although in this glomerulonephritis model specific MIF response after specific stimulation in vitro as well as DTH reactions could be detected against immune complexes or their constituents, these immune reactions seem not to play important role in this ECGN in particular with respect to the proteinuria.In heterologous immune complex glomerulonephritis glomerular deposition of immune complexes occurs immediately after an injection with heterologous antibody directed against antigen, derived from the brush border of the tubules. The injected antibody is thought to combine with circulating Fx1A antigen to form immune complexes which subsequently are deposited in the glomeruli. However, perfusion of rat kidneys in absence of this antigen likewise resulted in prompt localization of immune complexes along the glomerular basement membrane. Further, Fx1A antigen was shown to be present in the capillary wall, especially in the filtration slits and on the cell membrane of epithelial cells. From these findings it was concluded that in this model of glomerulonephritis the deposited immune complexes are formed locally instead of being deposited from the circulation. This concept of fixed antigen may also be relevant to the pathogenesis of other forms of experimental glomerulonephritis and probably also for human glomerulonephritis.

Studies on the Mechanism of Binding and Uptake of Immune Complexes by Various Cell Types of Rat Liver in Vivo

Soluble heterologous immune complexes (IC) were used to study the mechanism of IC binding to rat liver in vivo. Binding of IC to the various cell types of the liver, endothelial cells, hepatocytes. and Kupffer cells, was only inhibited by aggregated swine immunoglobulins. Binding was not inhibited by the absence of complement components. Intravenous injection of asialoglycoproteins. to block the galactose receptor, could not prevent IC binding. We conclude that Fc receptors play an important role in the binding of soluble heterologous IC to hepatocytes. endothelial cells, and Kupffer cells.

LYMPHOKINES IN SENSITIZED RATS .1. MIGRATION-INHIBITORY FACTOR(S) FROM SPECIFICALLY STIMULATED THYMOCYTES INVITRO

Cell-mediated immune responses were studied in Wistar rats by migration inhibition factor (MIF) assays in vitro of lymphoid cells derived from thymus, spleen and peripheral blood and peritoneal exudates and by delayed cutaneous hypersensitivity reactions in vivo. Using PPD and purified diphtheria toxoid as soluble test antigens it appeared that significant migration inhibition was observed only when sensitized thymus and peritoneal exudate cells were used in the direct capillary migration system. Indirect MIF assays, using both capillary and agarose techniques, showed that migration inhibitory activity was found in thymus culture supernatants as well as in spleen culture supernatants of sensitized animals. The MIF activity in thymic cell culture supernatants seemed to be antigen-independent, although in this respect no definitive conclusions can be drawn from the present results. Migration inhibition in direct and indirect techniques always correlated with a positive delayed-type skin reaction. It is suggested that a population of thymus cells of sensitized animals is able to produce MIF on specific antigenic stimulation in vitro. This might support the idea that a cell population within the thymus possesses characteristics of peripheral T cells.

Renal Antigens in Experimental Immune Complex Glomerulonephritis

The study of experimental glomerulonephritis has greatly extended our knowledge and understanding of human glomerulopathies. One of the models in experimental glomerulonephritis is the autologous immune complex glomerulonephritis (AIC), which was originally described by Heymann et al. (1959) and was given its present name by Edgington et al. (1967). They elucidated its pathogenesis and demonstrated glomerular deposition of immune complexes, consisting of an antigen normally present in the brush border of the proximal tubules of rat kidney and its specific antibody. The glomerulopathy can be induced in certain rat strains by immunization with a crude antigen fraction from the brush border (Fx1A) or with the purified nephritogenic antigen (RTEα5) in Freund’s complete adjuvant (Edgington et al., 1968). This procedure results after 6 weeks in glomerular deposition of immune complexes, which are localized exclusively at the epithelial side of the GBM. Morphologically and clinically the disease resembles human membranous glomerulopathy.