THE PATHOLOGIC EFFECTS OF INTRAVENOUSLY ADMINISTERED SOLUBLE ANTIGEN-ANTIBODY COMPLEXES : II. ACUTE GLOMERULONEPHRITIS IN RATS

FcγRIIb on liver sinusoidal endothelium clears small immune complexes

It has long been known that the ITIM-bearing IgG Fc receptor (FcγRIIb, RIIb) is expressed on liver sinusoidal endothelial cells (LSEC) and that the liver is the major site of small immune complex (SIC) clearance. Thus, we proposed that RIIb of LSEC eliminates blood-borne SIC, thereby controlling immune complex-mediated autoimmune disease. Testing this hypothesis, we found most RIIb of the mouse, fully three-quarters, to be expressed in liver. Moreover, most (90%) liver RIIb was expressed in LSEC, the remainder in Kupffer cells. An absent FcRγ in LSEC implied that RIIb is the sole FcγR expressed. Testing the capacity of liver RIIb to clear blood-borne SIC, we infused mice intravenously with radio-iodinated SIC made of OVA and rabbit IgG anti-OVA. Tracking decay of SIC from the blood, we found the RIIb knockout strain to be severely deficient in eliminating SIC compared with the wild-type strain, terminal half-lives being 6 and 1.5 h, respectively. RIIb on LSEC, a major scavenger, keeps SIC blood concentrations low and minimizes pathologic deposition of inflammatory immune complex.

Autoantibodies, autoimmune disease, and the birth of immune diagnostics

The appearance of autoantibody to DNA followed sequentially by the disappearance of anti-DNA and appearance of DNA antigen in a patient with systemic lupus erythematosus demonstrated that autoantibodies participate in immune complex-mediated pathogenesis. Continuing studies showed that autoantibodies are also useful biomarkers in clinical diagnosis and important reagents for elucidating the structure and function of intracellular proteins in cell biology. Recently, autoantibodies to tumor-associated antigens have been identified in cancer, and these findings have expanded the field of cancer immunodiagnostics.

Molecular bases of immune complex pathology

The binding of antigens with antibodies forms immune complexes in the body. Usually these complexes are eliminated by the system of mononuclear phagocytes without development of pathological changes. This review highlights principal mechanisms responsible for safe removal of immune complexes in primates and humans. Special attention is given to diseases known as "immune complex diseases", when antigen-antibody complexes induce inflammatory reactions. The review considers key experimental works that significantly contributed to current knowledge of etiology and pathogenesis of type III hypersensitivity. Some factors of the development of immune complex syndrome such as level of humoral immune response to antigen, isotype and affinity of forming antibodies, the amount of immune complexes, and the consequences of their interaction with the complement system and Fc-receptors are analyzed based on the molecular mechanisms involved. The review contains a retrospective analysis of the most significant scientific achievements in immune complex pathology investigation within the last 100 years.

Pathology of lupus nephritis

The glomerular pathology of lupus nephritis is the result of diverse immune insults which are probably of independent pathogenetic origins. Although lupus nephritis is looked upon as a classic example of immune complex-induced microvascular injury resulting from circulating DNA double stranded polynucleotide antigens/anti-DNA antibody complexes, other mechanisms, including in situ reactivity of free antibody with fixed antigens and the role of sensitized T-cells, are probably an important part of the picture. This complexity makes categorization of glomerular pathology into a clinically relevant classification an important goal so that our experiences can be reliably compared. This review describes the various glomerular lesions commonly encountered in lupus nephritis and, based upon data derived from experimental models, emphasizes the importance of understanding the clinical relevance of the reported morphology. We point out that the severity of glomerular damage is not merely the accrued result of immune complex induced injury to individual capillaries, but involves capillary necrosis and thrombosis, neither of which may have anything to do with immune complexes or immune aggregates. In fact, the segmental lesions of glomerular capillary necrosis and thrombosis may have a great deal to do with the response to therapy and the ultimate outcome of the patient. While discrete morphologic lesions such as mesangiopathy, acute inflammation, necrosis, thrombosis, epimembranous lesions and podocytopathy are readily described, it is important to note that any given case can represent any combination of these insults. In this context, the new proposed International Society of Nephrology Classification is presented and its strengths and weaknesses discussed.

The pathologic effects of intravenously administered soluble antigen-antibody complexes. I. Passive serum sickness in mice

The intravenous administration to mice of soluble antigen-antibody complexes in antigen excess resulted in a high incidence of glomerulonephritis and less frequently in endocarditis or arteritis. These lesions are present within 48 hours of the first of 3 injections and disappear within 2 weeks. The same pathological changes were produced with complexes prepared from either rabbit or chicken antibody. In the case of rabbit antibody, the severity of the glomerulonephritis was greater with the ovalbumin antiovalbumin system than with the BSA system. Anaphylaxis regularly occurred in mice given complexes prepared from rabbit antibody, but was not seen following administration of complexes prepared from chicken antibody. Pretreatment with cortisone diminished the severity of the glomerulo-nephritis and resulted in accumulation of amorphous, eosinophilic material within glomerular capillaries in mice injected with antigen-antibody complexes. The rabbit antibody used in these experiments failed to sensitize guinea pig skin to passive cutaneous anaphylaxis when injected in the form of soluble complexes. This indicates that these complexes do not dissociate to a detectable extent in vivo and thus favors the interpretation that complexes localize as such in the sites where tissue damage occurs. Chicken anti-mouse erythrocyte antibody produced hemolysis of mouse red cells in the presence of mouse complement. In contrast to a similar rabbit anti-serum, the hemolytic activity of the chicken antibody with mouse complement was very slight. This suggests that complement does not play an important role in the pathogenesis of these experimental lesions.

Glomerulonephritis induced in sheep by injections of heterologous glomerular basement membrane and Freund's complete adjuvant

Sheep injected every 2 weeks with heterologous GBM and Freund's adjuvant by any one or combination of the following routes: intramuscular, subcutaneous, or intradermal, develop uniformly a fulminating, extracapillary glomerulonephritis, invariably fatal within 27 to 90 days after the first injection. The chief histologic feature is marked fibroepithelial proliferation of Bowman's capsule with crescent formation. The appearance of the lesions resembles the acute, subacute, and chronic stages of human glomerulonephritis, and depends on when the animal was sacrificed. Freund's adjuvant or heterologous GBM alone does not produce such a nephritis. The combination of placental tissue and Freund's adjuvant under the present experimental conditions was also unable to produce a nephritis. The clinical course, increase in nitrogen retention, evolution of renal lesions, and death, all describe a fulminating disease. The disease most characteristically resembles fatal, fulminating human subacute glomerulonephritis. The changes in serum proteins, decrease in serum albumin, and increase in serum globulin, occurred approximately the same in both the GBM-treated and the control adjuvant group. Similar changes have been reported from hyperimmunization alone, and so it is not clear how much these changes are due to immunization and how much is due to the nephritic process. The changes in serum cholesterol were not considered statistically significant. Circulating serum antibodies which localized (by fluorescent antibody technique in vitro) on basement membrane structures of the heterologous donor kidney antigen or which produced nephritis in the heterologous donor species (rat and dog) were found in serum of sheep sick or dying of nephritis. The passive transfer of nephritis by serum antibodies marks the first successful instance of transfer of nephritis by serum antibody to a heterologous species from an animal which had developed nephritis itself. The serum antibodies involved in the transfer of disease to the donor species appear to be unrelated to the mediators of nephritis in the sheep and may represent only the previously known heteronephrotoxic antibodies. By various biologic criteria the sheep nephritis presumably occurs by an autoimmune mechanism. However, it is not known whether the sheep nephritis is mediated by sensitized cells and/or antibodies. The latent period was estimated to end about 16 to 71 days after the first injection. Azotemia was estimated to begin about 17 to 78 days after the first injection. Proteinuria and azotemia began approximately 23 and 13 days before death. The rapid progression to a fatal termination defined the fulminating character of this disease.

Pathological studies on nephrotoxic serum nephritis accelerated with rabbit gamma-globulin in mice

In order to characterize nephrotoxic serum nephritis accelerated with rabbit gamma-globulin in mice, histopathological studies were carried out 15 days after NTS injection, the time when increases in urinary protein and serum cholesterol and a decrease in serum albumin were apparent. Characteristic changes were widespread thickening of glomerular capillary walls and widening of mesangial areas, owing to deposits of mesangial matrixlike substances. The mesangial interposition into subendothelial areas and the resultant narrowing of the capillary lumen were shown ultrastructurally. In severely affected glomeruli, a hyaline nodular lesion was observed. Visceral epithelial cells demonstrated fusion of the foot processes, microvilli formation, occasional proliferation, and enlargement. Parietal epithelial cells proliferated, forming a cellular crescent. Based on these characteristics, it appears this nephritic model shares a common pathology with human membranoproliferative glomerulonephritis type 1 and crescentic glomerulonephritis and can be considered an appropriate model for producing severe nephritis for short periods.

Some hemodynamic determinants of immune complex trapping by the kidney

This study was undertaken to help clarify the relationship between capillary hemodynamic events and the tissue uptake of circulating immune complexes (IC). In each of 23 dogs, bovine serum albumin (BSA) and rabbit antiBSA soluble IC labeled with 125I were given by constant i.v. infusion, and IC uptake by a normally perfused kidney was compared to that of the contralateral kidney in which renal blood flow (RBF) was changed by renal artery constriction or raised ureteral pressure. In these same animals, IC uptake in 15 other major organ systems was also measured simultaneously. During IC infusion microspheres of 85Sr were injected to measure cardiac output and tissue blood flow, and red cells labeled with 51Cr were infused to mark tissue vascular volume. At completion of the IC infusion, tissue samples were taken from the kidneys and the 15 other major organs systems. From the isotope content of each tissue, we determined IC content, blood flow rate, vascular transit time, and fractional uptake of IC (FIC). In addition, glomeruli were isolated from renal cortex to assess IC uptake in glomerular versus renal nonglomerular tissue. We found that 1) for kidney, IC delivery rate, capillary hydrostatic pressure, and capillary ultrafiltration rate are less important than the plasma IC concentration in determining IC uptake; 2) for each organ studied, the principal determinant of IC uptake per gram of tissue, at any given PIC, is vascular volume per gram of tissue; 3) tissue vascular volume per gram of tissue may determine IC uptake per gram of tissue because tissue vascular volume determines the capillary surface area in contact with circulating IC or because tissue vascular volume determines tissue vascular transit time, at any given tissue blood flow rate.

Antinuclear antibodies (ANA): immunologic and clinical significance

The methods currently used for the detection of ANA have been analyzed, with emphasis on their practical application to the diagnosis of the CTD. The use of the indirect IF-ANA test was recommended as a screening procedure to detect ANA. The need to standardize the technique using a single substrate and fluorescent conjugates with uniform F/P ratios was stressed. Most importantly, the value of titrating ANA for the diagnosis of the CTD was discussed. ANA titers higher than 1/500 are usually very significant clinically, often found in spontaneous or drug-induced SLE and few other CTD. The immunologic aspects of ANA and their potential value as aids in the diagnosis and management of the CTD were discussed. Anti-nDNA antibodies have been found to have a high degree of specificity for SLE and high titers of these antibodies correlate well with low levels of serum complement and severity of kidney involvement. The spectrum of ANA in the sera from patients with SLE has been expanded with the finding of anti-Sm antibodies which, when detected by gel precipitation with prototype serum, have been found so far only in SLE. Some of these antibodies have been found to have prognostic significance. Patients with MCTD and a group of patients with SLE have high titers of serum ANA with specificity for an RNase-sensitive component of ENA. The group of SLE patients defined by the presence of these antibodies (anti-Mo) have a better prognosis and in general develop only mild nephritis or have no kidney involvement at all. High titers of pure antinucleolar antibodies probably are found almost exclusively in the sera of patients with scleroderma. Some ANA have organ specificity, and GS-ANA have been found in all patients with Felty's syndrome and in a large proportion of patients with RA. One of the great advances in the field has been the recognition that ANA can be induced in the human and in experimental animals by the use of a number of therapeutic agents. Some of these agents can also induce a clinical picture resembling spontaneous SLE, though kidney involvement does not occur or is extremely mild. It is interesting that the whole spectrum of ANA can be found in drug-induced LE except anti-nDNA antibodies which have been associated to the pathogenesis of immune complex nephritis in spontaneous SLE. There is no doubt that research on ANA has contributed a great deal to the understanding of the CTD and will continue to be a valuable tool for the clinician and the investigator.

Electron microscopic studies of human glomerulonephritis with ferritin-conjugated antibody. Localization of antigen-antibody complexes in glomerular structures of patients with acute glomerulonephritis

1. Kidney biopsies from 4 cases of severe acute glomerulonephritis were obtained 11 to 25 days after the onset of clinical manifestations of the disease. These tissues were treated with ferritin-conjugated antibodies to 7S gamma-globulin, beta(1C), and Type 12 streptococcal products. Adjacent pieces of the biopsied material were treated with control ferritin-labeled antisera or with ferritin alone. As further controls, normal renal tissue and renal tissue from patients with other kidney diseases were treated with the same antisera. The 3 antisera to 7S gamma-globulin, beta(1C) and Type 12 streptococcus were specifically bound in electron-opaque foreign material in the following renal areas: (a) the lumen of glomerular capillaries; (b) medullary arteriolar walls (2 cases); (c) pinocytic vacuoles and absorption droplets of endothelial or mesangial cells; (d) canals between proliferating mesangial or endothelial cells which connect the capillary lumen with the deep mesangial region or with the endothelial side of the basement membrane; (e) basement membrane proper; (f) subendothelial and certain subepithelial deposits; and (g) Bowman's space. 2. None of the 3 ferritin-conjugated antisera listed above were bound to the nuclei of glomerular cells or to portions of the cytoplasm other than those specified. 3. Ferritin-conjugated antisera to pneumococcus Type II and vaccinia virus and ferritin alone were not bound to any structures in the glomerular tissue. 4. None of the ferritin-conjugated antisera bound to normal renal tissue or to kidney tissue from other renal disease. 5. The data obtained are compatible with the following working hypothesis: Antigen-antibody aggregates of Type 12 streptococcal products, gamma-globulin, and complement are present in the circulating blood of patients with severe acute glomerulonephritis. Large amounts of the complexes are caught in the filtering system of the glomeruli. The inflammatory reactions seen in the glomerular structures result from the presence of the immune complexes and of the polymorphonuclear leukocytes which conjointly may be responsible for the disease.

Homologous disease in the adult rat, a model for autoimmune disease. II. Findings in the joints, heart, and other tissues

Polyarthritis and cardiac lesions have been observed in the adult rat with homologous disease. Changes in the lymphoid tissue and kidney have also been noted. A migratory polyarthritis occurred in over half of the affected animals, and cardiac involvement of varying intensity was present in all. Histologically, the arthritis was characterized by a mononuclear synovial inflammatory reaction. In the heart, the valves and myocardium demonstrated a similar type of response. Cultures of involved joints and hearts for pyogens and pleuropneumonia-like organisms were negative. The lymphoid tissues showed progressive changes in three stages: (a) disappearance of follicles; (b) increase in plasma-like cells and histiocytes; and (c) fibrosis. The second stage tended to coincide with the development of the polyarthritis. The kidney showed mild interstitial mononuclear infiltration. The pathologic changes described appear to be a consequence of reaction between foreign immunologically competent cells and host antigens, but the possibility that these lesions represent a response to antigens derived from unknown infectious agents is, however, not ruled out.