Epidemic acute glomerulonephritis associated with type 49 streptococcal pyoderma. II. Correlative study of light, immunofluorescent and electron microscopic findings

Clinico-Pathogenic Similarities and Differences between Infection-Related Glomerulonephritis and C3 Glomerulopathy

Recently, the comprehensive concept of "infection-related glomerulonephritis (IRGN)" has replaced that of postinfectious glomerulonephritis (PIGN) because of the diverse infection patterns, epidemiology, clinical features, and pathogenesis. In addition to evidence of infection, hypocomplementemia particularly depresses serum complement 3 (C3), with endocapillary proliferative and exudative GN developing into membranoproliferative glomerulonephritis (MPGN); also, C3-dominant or co-dominant glomerular immunofluorescence staining is central for diagnosing IRGN. Moreover, nephritis-associated plasmin receptor (NAPlr), originally isolated from the cytoplasmic fraction of group A Streptococci, is vital as an essential inducer of C3-dominant glomerular injury and is a key diagnostic biomarker for IRGN. Meanwhile, "C3 glomerulopathy (C3G)", also showing a histological pattern of MPGN due to acquired or genetic dysregulation of the complement alternative pathway (AP), mimics C3-dominant IRGN. Initially, C3G was characterized by intensive "isolated C3" deposition on glomeruli. However, updated definitions allow for glomerular deposition of other complement factors or immunoglobulins if C3 positivity is dominant and at least two orders of magnitude greater than any other immunoreactant, which makes it challenging to quickly distinguish pathomorphological findings between IRGN and C3G. As for NAPlr, it was demonstrated to induce complement AP activation directly in vitro, and it aggravates glomerular injury in the development of IRGN. A recent report identified anti-factor B autoantibodies as a contributing factor for complement AP activation in pediatric patients with PIGN. Moreover, C3G with glomerular NAPlr deposition without evidence of infection was reported. Taken together, the clinico-pathogenic features of IRGN overlap considerably with those of C3G. In this review, similarities and differences between the two diseases are highlighted.

Nephritis-Associated Plasmin Receptor (NAPlr): An Essential Inducer of C3-Dominant Glomerular Injury and a Potential Key Diagnostic Biomarker of Infection-Related Glomerulonephritis (IRGN)

Nephritis-associated plasmin receptor (NAPlr) was originally isolated from the cytoplasmic fraction of group A Streptococci, and was found to be the same molecule as streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and plasmin receptor (Plr) on the basis of nucleotide and amino acid sequence homology. Its main functions include GAPDH activity, plasmin-binding capacity, and direct activation of the complement alternative pathway (A-P). Plasmin trapped by deposited NAPlr triggers the degradation of extracellular matrix proteins, such as glomerular basement membranes and mesangial matrix, and the accumulation of macrophages and neutrophils, leading to the induction of plasmin-related endocapillary glomerular inflammation. Deposited NAPlr at glomerular endocapillary site directly activates the complement A-P, and the endocapillary release of complement-related anaphylatoxins, C3a and C5a, amplify the in situ endocapillary glomerular inflammation. Subsequently, circulating and in situ-formed immune complexes participate in the glomerular injury resulting in NAPlr-mediated glomerulonephritis. The disease framework of infection-related glomerulonephritis (IRGN) has been further expanded. GAPDH of various bacteria other than Streptococci have been found to react with anti-NAPlr antibodies and to possess plasmin-binding activities, allowing glomerular NAPlr and plasmin activity to be utilized as key biomarkers of IRGN.

Clinical and Pathophysiological Insights Into Immunological Mediated Glomerular Diseases in Childhood

The kidney is often the target of immune system dysregulation in the context of primary or systemic disease. In particular, the glomerulus represents the anatomical entity most frequently involved, generally as the expression of inflammatory cell invasion or circulant or in situ immune-complex deposition. Glomerulonephritis is the most common clinical and pathological manifestation of this involvement. There are no universally accepted classifications for glomerulonephritis. However, recent advances in our understanding of the pathophysiological mechanisms suggest the assessment of immunological features, biomarkers, and genetic analysis. At the same time, more accurate and targeted therapies have been developed. Data on pediatric glomerulonephritis are scarce and often derived from adult studies. In this review, we update the current understanding of the etiologic events and genetic factors involved in the pathogenesis of pediatric immunologically mediated primitive forms of glomerulonephritis, together with the clinical spectrum and prognosis. Possible new therapeutic targets are also briefly discussed.

Epidemiology, pathogenesis, treatment and outcomes of infection-associated glomerulonephritis

For over a century, acute 'post-streptococcal glomerulonephritis' (APSGN) was the prototypical form of bacterial infection-associated glomerulonephritis, typically occurring after resolution of infection and a distinct infection-free latent period. Other less common forms of infection-associated glomerulonephritides resulted from persistent bacteraemia in association with subacute bacterial endocarditis and shunt nephritis. However, a major paradigm shift in the epidemiology and bacteriology of infection-associated glomerulonephritides has occurred over the past few decades. The incidence of APSGN has sharply declined in the Western world, whereas the number of Staphylococcus infection-associated glomerulonephritis (SAGN) cases increased owing to a surge in drug-resistant Staphylococcus aureus infections, both in the hospital and community settings. These Staphylococcus infections range from superficial skin infections to deep-seated invasive infections such as endocarditis, which is on the rise among young adults owing to the ongoing intravenous drug use epidemic. SAGN is markedly different from APSGN in terms of its demographic profile, temporal association with active infection and disease outcomes. The diagnosis and management of SAGN is challenging because of the lack of unique histological features, the frequently occult nature of the underlying infection and the older age and co-morbidities in the affected patients. The emergence of multi-drug-resistant bacterial strains further complicates patient treatment.

A unified pathogenesis for kidney diseases, including genetic diseases and cancers, by the protein-homeostasis-system hypothesis

Every cell of an organism is separated and protected by a cell membrane. It is proposed that harmony between intercellular communication and the health of an organism is controlled by a system, designated the protein-homeostasis-system (PHS). Kidneys consist of a variety of types of renal cells, each with its own characteristic cell-receptor interactions and producing characteristic proteins. A functional union of these renal cells can be determined by various renal function tests, and harmonious intercellular communication is essential for the healthy state of the host. Injury to a kind of renal cells can impair renal function and induce an imbalance in total body health. Every acute or chronic renal disease has unknown etiologic substances that are responsible for renal cell injury at the molecular level. The immune/repair system of the host should control the etiologic substances acting against renal cells; if this system fails, the disease progresses to end stage renal disease. Each renal disease has its characteristic pathologic lesions where immune cells and immune proteins, such as immunoglobulins and complements, are infiltrated. These immune cells and immune proteins may control the etiologic substances involved in renal pathologic lesions. Also, genetic renal diseases and cancers may originate from a protein deficiency or malfunctioning protein under the PHS. A unified pathogenesis for renal diseases, including acute glomerulonephritis, idiopathic nephrotic syndrome, immunoglobulin A nephropathy, genetic renal diseases such as Alport syndrome, and malignancies such as Wilms tumor and renal cell carcinoma, is proposed using the PHS hypothesis.

C3 glomerulopathy and current dilemmas

C3 glomerulopathy (C3G) is a recently identified disease entity caused by dysregulation of the alternative complement pathway, and dense deposit disease (DDD) and C3 glomerulonephritis (C3GN) are its components. Because laboratory detection of complement dysregulation is still uncommon in practice, "dominant C3 deposition by two orders greater than that of immunoglobulins in the glomeruli by immunofluorescence", as stated in the consensus report, defines C3G. However, this morphological definition possibly includes the cases with glomerular diseases of different mechanisms such as post-infectious glomerulonephritis. In addition, the differential diagnosis between DDD and C3GN is often difficult because the distinction between these two diseases is based solely on electron microscopic features. Recent molecular and genetic advances provide information to characterize C3G. Some C3G cases are found with genetic abnormalities in complement regulatory factors, but majority of cases seem to be associated with acquired factors that dysregulate the alternative complement pathway. Because clinical courses and prognoses among glomerular diseases with dominant C3 deposition differ, further understanding the background mechanism, particularly complement dysregulation in C3G, is needed. This may resolve current dilemmas in practice and shed light on novel targeted therapies to remedy the dysregulated alternative complement pathway in C3G.

Post-streptococcal glomerulonephritis associated with atypical hemolytic uremic syndrome: to treat or not to treat with eculizumab?

A 7-year-old male with poststreptococcal glomerulonephritis (PSGN) developed hemolytic uremic syndrome (HUS) and achieved remission. He was treated with eculizumab for 1 year. The eculizumab was discontinued and the patient remained in remission. This is the 10th reported case of PSGN associated with HUS. The histopathological feature observed at the 1-year follow-up was indistinguishable from the expected findings in an individual with healed PSGN without associated HUS. The relatively good prognosis in most prior cases and the absence of any reported recurrences strongly suggest that this form of atypical HUS does not warrant long-term eculizumab therapy.

Streptococcal Infection-related Nephritis (SIRN) Manifesting Membranoproliferative Glomerulonephritis Type I

We herein report the case of an 18-year-old boy who developed nephrotic syndrome and hypertension after upper airway inflammation. Post-streptococcal acute glomerulonephritis was diagnosed on the basis of a high antistreptolysin O titer, hypocomplementemia, proteinuria, and microscopic hematuria. A renal biopsy was performed due to persistent proteinuria, and the pathological diagnosis was membranoproliferative glomerulonephritis (MPGN) type I. Glomeruli showed positive staining for nephritis-associated plasmin receptor (NAPlr), a nephritogenic group A streptococcal antigen, and plasmin activity was found in a similar distribution as NAPlr deposition. This rare case of streptococcal infection-related nephritis (SIRN) manifesting MPGN type I supports the histological diversity of SIRN.

A common immunopathogenesis mechanism for infectious diseases: the protein-homeostasis-system hypothesis

It was once believed that host cell injury in various infectious diseases is caused solely by pathogens themselves; however, it is now known that host immune reactions to the substances from the infectious agents and/or from the injured host cells by infectious insults are also involved. All biological phenomena in living organisms, including biochemical, physiological and pathological processes, are performed by the proteins that have various sizes and shapes, which in turn are controlled by an interacting network within the living organisms. The author proposes that this network is controlled by the protein homeostasis system (PHS), and that the immune system is one part of the PHS of the host. Each immune cell in the host may recognize and respond to substances, including pathogenic proteins (PPs) that are toxic to target cells of the host, in ways that depend on the size and property of the PPs. Every infectious disease has its own set of toxic substances, including PPs, associated with disease onset, and the PPs and the corresponding immune cells may be responsible for the inflammatory processes that develop in those infectious diseases.

Clinical and histologic resolution of poststreptococcal glomerulonephritis with large subendothelial deposits and kidney failure

A 16-year-old male adolescent who had fallen and scratched his knee developed cold-like symptoms. Gross hematuria, oliguria, and peripheral edema appeared about 2 weeks after his fall. Tests showed hypocomplementemia, increased antistreptolysin O titers, and severe kidney failure with hematuria/proteinuria. Kidney biopsy showed endocapillary proliferative glomerulonephritis visible using light microscopy and deposits of complement C3 on capillary walls, detectable using immunofluorescence microscopy. Although these findings suggested that he had acute poststreptococcal glomerulonephritis (APSGN), electron microscopy failed to detect subepithelial humps, a feature typical of APSGN; instead, massive electron-dense deposits were visible in the subendothelial space. A second biopsy performed 3 months later showed mesangial cell proliferation without endocapillary proliferation using light microscopy and the disappearance of subendothelial electron-dense deposits in electron micrographs, suggesting that APSGN had resolved. Glomerular deposition of nephritis-associated plasmin receptor, a nephritogenic streptococcal antigen, was observed in the first biopsy specimen, but not the second. The patient required 4 hemodialysis treatments, and within 1 year of supportive therapy only, kidney function and urinalysis had normalized. This is an interesting case of APSGN presenting with acute kidney injury and atypical massive subendothelial deposits, but no subepithelial deposits on electron microscopy, a pattern resembling that in membranoproliferative glomerulonephritis type I.

Post-streptococcal acute glomerulonephritis in children: clinical features and pathogenesis

Post-streptococcal acute glomerulonephritis (PSAGN) is one of the most important and intriguing conditions in the discipline of pediatric nephrology. Although the eventual outcome is excellent in most cases, PSAGN remains an important cause of acute renal failure and hospitalization for children in both developed and underdeveloped areas. The purpose of this review is to describe both the typical and less common clinical features of PSAGN, to outline the changes in the epidemiology of PSAGN over the past 50 years, and to explore studies on the pathogenesis of the condition with an emphasis on the search for the elusive nephritogenic antigen.

Exposure to organic solvents--a missing link in poststreptococcal glomerulonephritis?

Fifteen patients with evidence of acute poststreptococcal glomerulonephritis were asked about their contact with vapours of organic solvents. Six patients reported brief exposure shortly before the onset of glomerulonephritis, 4 fairly long exposure, and 5 none or insignificant. At the latest followup, 3 of 4 patients who were still exposed to such solvents had proteinuria and a low glomerular filtration rate (GFR), and 2 were hypertensive. Of the 11 patients who had never been or were no longer exposed, the GFR was insignificantly decreased in 2, none had proteinuria and none were hypertensive. Fifteen age-and sex-matched controls, who had been infected with group A beta-hemolytic streptococci, T type 12, had not been exposed, or the exposure was insignificant and not related to the streptococcal infection. Exposure to organic solvents or other nephrotoxic agents may be the condition which determines the outcome of an infection with nephritogenic streptococci.

Ultrastructural observations in a case of BK virus nephropathy with viruses in glomerular subepithelial humps

BK virus nephropathy is a known cause of renal transplant dysfunction and failure. The disease is identified by examination of kidney biopsy tissue utilizing histopathological techniques. Ultrastructural examination of two glomeruli revealed pathology within one glomerulus. Glomerular basement membranes contained subepithelial humps of deposit-like material and BK viruses were identified within this material. Viruses were identified within intertubular capillaries. There was evidence of cytoplasmic clearance of viruses from the glomerular basement membrane by podocytes. The findings may be relevant to the investigation of hump formation and antigen clearance in BK virus nephropathy and postinfectious glomerulonephritis.

Immunoglobulin G has a role for systemic protein modulation in vivo: a new concept of protein homeostasis

The constant level of various proteins including albumin and cellular components in intravascular pool in vivo is strictly controlled by an unknown homeostatic mechanism, although there are fluctuations seen in pathologic conditions. Because the majority of the IgG in the serum is regarded as self-reactive natural autoantibodies, IgG may have a role to react with all proteins in vivo. It is hypothesized that like an immune system, a homeostatic mechanism for the protein pool also has a sensitive role to identify and memorize the extent and repertoire of both normal and pathogenic proteins on an individual basis, and IgG may be one of the major players in performing these functions. This hypothesis may explain the unresolved clinical observations as followed: (1) the marked increased IgG levels observed in self-limiting diseases presumed to come from immunological insults such as acute poststreptococcal glomerulonephritis and Kikuchi-Fujimoto disease, (2) an immediate reduction of all protein levels except immunoglobulins after intravenous immunoglobulin (IVIG) treatment in Kawasaki disease, (3) a unified explanation for the variety of immunomodulating effects exerted by IVIG, (4) the IgG-enzyme complexes observed in benign conditions such as macroamylasemia and hyperphosphatasemia, and (5) the marked decreased IgG level, which is correlated with the albumin level in minimal change nephrotic syndrome. IgG may be a 'watch-dog' for the disturbances of protein homeostasis in vivo. IgG may control the pathogenic proteins that appeared in disordered states, and it may help prevent the loss of proteins in case of nephrotic syndrome.

TGF-beta and the endothelium during immune injury

During immune injury, activation of endothelial cells by inflammatory cytokines stimulates leukocyte adhesion to the endothelium, turns the endothelium from an anticoagulant surface to one that is frankly procoagulant, and results in the release of vasoactive mediators and growth factors. Cytokine activation of endothelial cells also results in increased endothelial cell TGF-beta 1 synthesis and enhanced activation of latent TGF-beta, the latter involving a shift of plasmin production from the apical to subendothelial surface. In cytokine-stimulated endothelial cells, TGF-beta hinders leukocyte adhesion and transmigration via inhibition of IL-8 and E-selectin expression. TGF-beta also profoundly diminishes cytokine-stimulated inducible nitric oxide synthase production and instead augments endothelial nitric oxide synthase expression. Thus, some of the TGF-beta actions on endothelium during immune activation can viewed as immunosuppressive. TGF-beta also influences mechanisms of vascular remodeling during the healing phase of immune injury. It stimulates PDGF-B synthesis by endothelial cells, causes bFGF release from subendothelial matrix, and promotes VEGF synthesis by non-endothelial cells. Together these mediators control angiogenesis, a critical component of the vascular repair phenomenon. Further, endothelial cell derived PDGF-B and bFGF influence the proliferation and migration of neighboring cells. Thus, endothelial cells and TGF-beta actions on the endothelium play important roles both during the initial phase of immune injury and during the later remodeling phase.

The current spectrum of infectious glomerulonephritis. Experience with 76 patients and review of the literature

To identify the demographic, clinical, and pathologic features and the prognosis of renal disease in a series of patients with infectious or postinfectious proliferative glomerulonephritis (GN), data were collected from records of 76 adult patients admitted from 1976 to 1993 to 2 neighboring suburban hospital nephrology units, whose catchment population consists of patients living in a suburban borough of Paris with a below-average socioeconomic status. Thirty-four patients (45%) were alcoholics, diabetics, or intravenous illicit-drug users. Sixty-six patients presented with acute nephritic and/or nephrotic syndrome. Acute renal failure was present in 56 (76%) and required dialysis in 14. The diagnostic workup comprised at least 1 renal biopsy in each case. The patient's background, site of infection, clinical course, laboratory variables, and, when available, bacteriologic findings were analyzed in each case to interpret the evolution of the disease. Initial renal biopsy disclosed endocapillary GN in 44 patients, crescentic GN in 26, and membranoproliferative GN in 6. Ten patients had endocarditis. Staphylococci and Gram-negative strains, not streptococci, were the most common bacteria identified. The origin of sepsis was mainly the oropharynx (21), the skin (19) and the lung (14); 19 cases involved multiple sites of infection. Eight patients died (11%), and 20 (26%) recovered renal function, but GN followed a chronic course in 38 (50%), rapidly requiring maintenance dialysis in 6. Poor prognostic factors included age over 50 years, purpura, endocarditis, and glomerular extracapillary proliferation. Twenty-six patients underwent repeat renal biopsy 1 month to 11 years after the initial presentation. The main finding, irrespective of the interval since the first biopsy, was that ongoing or new iatrogenic infection acquired during hospitalization was almost invariably acquired during hospitalization was almost invariably associated with developing glomerular proliferative changes. This study shows that infectious proliferative GN remains common, but that its epidemiology has changed from what was observed until 2 decades ago. The responsible bacteria, when identified, now comprise a majority of staphylococci and Gram-negative strains, in contrast to the streptococci which predominated 3 decades ago. Infectious GN affects with increasing frequency patients with an underlying condition responsible for immunosuppression, especially alcoholism, even in the absence of cirrhosis. Destructive glomerular proliferation persists, especially but not exclusively until infection has been eradicated, and despite rescue treatment with corticosteroids and/or cytostatic drugs. Thus, the prognosis is poor, and infectious GN often ends in renal death. Infection continues in this decade to represent a frequent and probably often overlooked cause of end-stage renal failure.(ABSTRACT TRUNCATED AT 400 WORDS)

Neutrophil adhesion to glomerular mesangial cells: regulation by lipoxygenase-derived eicosanoids

Our results suggest that leukotrienes promote rapid PMN adhesion to glomerular mesangial cells via actions on PMN (LTB4) and mesangial cells (LTD4). Leukotriene-induced adhesion appeared to be mediated by a CD11/CD18-dependent (LTB4) and -independent (LTD4) mechanisms. The specific epitopes mediating LTD4-induced adhesion remain to be defined. Lipoxins did not influence basal adhesion. In contrast, lipoxins markedly inhibited LTD4-, but not LTB4-induced responses. Further elucidation of the components of these adhesion processes, of the pathways for leukotriene and lipoxin biosynthesis in the inflamed glomerulus, and of the counterregulatory actions of lipoxins and leukotrienes may reveal sites for therapeutic intervention in GN. (graph; see text) Data are mean +/- SE of 3 experiments, each conducted in quadruplicate. Leukotriene-induced adhesion was not inhibited by vehicle alone.

Determinants of immune complex-mediated glomerulonephritis

We have studied the influence of steric factors on the clinico-pathologic expression of immune complex-mediated glomerular diseases, utilizing ferritin as an exogenous antigen. The tracer was planted in the left kidney either in the subepithelial layer of the glomerular capillary wall or on the endothelium and lamina rara interna. Subepithelial immune complex formation resulted in non-inflammatory injury with heterologous and autologous proteinuric phases (115 +/- 16 mg/24 hrs on day 2; 183 +/- 16 mg/24 hrs on day 9) lasting four to five weeks. The glomerular filtration rate of the experimental left kidney was reduced by 19% at day 3, and was increased by 20% at day 12 over right kidney values. Immune complexes persisted for more than seven weeks in the lamina rara externa. In contrast, immune complex deposition on the endothelium and in the lamina rara interna led to acute transient anuria, with a 38% drop in glomerular filtration rate at one hour, massive platelet accumulation, followed by a strong inflammatory response. Proteinuria did not develop. Functional and structural integrity was restored within 24 hours, with complete clearing of immune deposits. We conclude that the distribution of exogenous antigens within the capillary wall determines the structural and functional expression of immune-mediated glomerular diseases.

Acute poststreptococcal glomerulonephritis mimicking Henoch-Schönlein purpura

Two children with acute glomerulonephritis, cutaneous vasculitis, and abdominal pain are reported. One child also had transient arthralgia and gastrointestinal hemorrhage. Although the clinical presentation mimicked many of the features of Henoch-Schönlein purpura, both patients had unusual variants of poststreptococcal glomerulonephritis.

The differential diagnosis of crescentic glomerulonephritis. The pathology of specific lesions with prognostic implications

Combined findings from light and electron microscopy with immunofluorescence studies make a definitive diagnosis possible in most cases of crescentic glomerulonephritis. The patient's prognosis and pattern of response to therapy are matters of immediate concern in the light of recent developments in nephrology. The frequency of crescentic lesions varies depending on the specific types of disease, but the idiopathic lesion is seldom seen.

Transplantation in mesangiocapillary glomerulonephritis with intramembranous dense "deposits": recurrence of disease

Six patients with mesangiocapillary glomerulonephritis and intramembranous dense "deposits" developed terminal renal failure and were transplanted, three from living and three from cadaver donors. Eight renal biopsy specimens were obtained from five of the grafts, from 1 to 26 months following transplantation. All six biopsy specimens taken later than seven months following the graft showed recurrence of dense intramembranous "deposits" in the basement membranes of glomeruli, and of Bowman's capsule and tubular basement in five. Recurrence of "deposits" was associated with deposition of C3 on immunofluorescent study in all but one specimen; in addition, IgM was found in two specimens, but IgG and early complement components were absent. Only two patients, however, showed glomerular proliferation associated with profuse proteinuria. In the other subjects the recurrence of the "deposit" was not associated with clinical findings. Graft loss, which occurred in two patients, was predominantly from rejection.

The role of complement, immunoglobulin and bacterial antigen in coagulase-negative staphylococcal shunt nephritis

We describe three patients with arrested hydrocephalus in whom glomerulonephritis developed secondary to Staphylococcus epidermidis bacteremia from an infected ventriculoatrial shunt. Investigation of the immune-mediated renal disease associated with this chronic infection showed that (1) complement depletion during the acute phase of bacteremia and nephritis was predominantly via the classic pathway; (2) rheumatoid factor was associated with bacteremia, fever, proteinuria and low complement levels; (3) early complement components (C1q, C4, C3), immunoglobulin (predominantly immunoglobulin M [IgM], Staph. epidermidis antigen(s) and electron denxe subendothelial deposits were localized within the renal glomerulus; (4) C1q, and IgM derived from patient serums, were the most prominent in vitro immunoreactants to Staph. epidermidis cell walls; and (5) the causative organisms, Staph. epidermidis, shared common antigens with Staph. aureus, and antibody from patient serums cross reacted with extracts from both of these organisms.

Immunopathologic mechanisms of renal disease

Anti-GBM antibodies and glomerular deposition of circulating immune complexes are responsible for the immunopathogenesis of about 5% and 75% of human glomerulonephritides, respectively. Anti-GBM antibodies most frequently cause rapidly progressive glomerulonephritides, respectively in about half of the patients with pulmonary hemorrhage, the Goodpasture's syndrome. Immune complexes cause a wide variety of glomerulonephritides, including diffuse and focal proliferative, membranous, membranproliferative and rapidly progressive morphologic varieties often accompanied by nephrotic syndrome. Immune complexes cause a wide variety of glomerulonephritides, including diffuse and focal proliferative, membranous, membranoproliferative and rapidly progressive morphologic varieties often accompanied by nephrotic syndrome. Immunopathologic tubulo-interstitial renal injury can be caused by antibodies reacting with TBM or by deposition of immune complexes in tubulo-interstitial tissue. Immunofluorescence studies of renal tissue supplemented by detection of circulating anti-basement membrane antibodies and immune complexes are essential in differentiating the immunopathologic mechanisms of glomerular and tubular injury, and are necessary adjuncts in evaluating patients with glomerulo- and tubulo-interstitial nephritis.

Self-induced glomerulonephritis

A patient is described who developed renal failure due to a severe proliferative glomerulonephritis with hypocomplementaemia and cryoglobulinaemia while repeatedly injecting herself with diphtheria, pertussis, and tetanus vaccine (D.P.T. vaccine). After stopping the antigen administration there was recovery of renal function, complement values returned to normal, and cryoglobulin could no longer be recovered from the sera. The pathogenesis of the glomerulonephritis is discussed.

Hypocomplementemic and normocomplementemic acute nephritis in children: a comparison with respect to etiology, clinical manifestations, and glomerular morphology

Of 182 patients with acute glomerulonephritis, 20 had normal C3 levels at onset. Normocomplementemic and hypocomplementemic patients were similar with respect to incidence and site of preceding streptococcal infection, elevation of ASO titer, distribution by age, sex, race, season, and year,\and glomerular morphology by light and electron microscopy. They differed in that the normocomplementemic patients tended to have normal serum C5 levels and, for reasons not clear, reduced serum albumin and elevated cholesterol levels. The consistent absence by immunofluorescence of IgG in the glomeruli of five hypocomplementemic patients and its presence in five normocomplementemic patients was considered a chance observation. The data suggest that in each group the nephritis was poststreptococcal and that the mechanism producing poststreptococcal glomerulonephritis is capable of acting independently of that activating circulating C3.

Properdin anc C3 proactivator: alternate pathway components in human glomerulonephritis

Serological and immunopathological studies of human glomerulonephritis have suggested that alternate pathways of activation of the third component of complement may be important in some forms of glomerulonephritis. We have investigated the role of two alternate pathway proteins, properdin and C3 proactivator, in 22 patients with chronic membranoproliferative glomerulonephritis, 21 patients with systemic lupus erythematosus, 20 patients with acute poststreptococcal glomerulonephritis, and 19 patients with other forms of renal disease. C3 (measured at beta(1)A), properdin, and C3 proactivator were assayed by single radial immunodiffusion. In sera with low beta(1)A (< 2 SD), mean properdin was most significantly decreased in patients with acute poststreptococcal glomerulonephritis but was also significantly decreased in chronic membranoproliferative glomerulonephritis and in untreated systemic lupus erythematosus. Properdin levels in other renal disease, acute glomerulonephritis, and chronic membranoproliferative glomerulonephritis with normal beta(1)A levels were not significantly different from normal. A positive correlation between beta(1)A and properdin levels in individual sera was present in all diseases except systemic lupus erythematosus. Serum C3 proactivator was markedly decreased in active systemic lupus erythematosus and there was a positive correlation between beta(1)A and C3 proactivator levels in systemic lupus erythematosus and other renal diseases but not acute poststreptococcal glomerulonephritis. Properdin in fresh sera from four patients with systemic lupus erythematosus and five with chronic membranoproliferative glomerulonephritis showed increased migration toward the cathode on immunoelectrophoresis, suggesting in vivo change of the properdin molecule. The observation of reduced serum levels of properdin and C3 proactivator and altered electrophoretic migration of properdin in some patients with glomerulonephritis provide new evidence for participation of these alternate pathway proteins in glomerulonephritis.

Changing types of nephritogenic streptococci in Trinidad

The relation of seven different M types of streptococci to acute glomerulonephritis associated with skin lesions in South Trinidad has been studied by means of type-specific antibody assays as well as by isolation and identification of the strains. The data indicate that, one after another, five of these strains have prevailed among patients with acute glomerulonephritis during the past five years. At least three of the strains (M-types 55, 49, 57, and/or 60) were associated with epidemic increases in nephritis cases. The appearance of five consecutively predominant types of nephritogenic streptococci during a relatively short period of time is in contrast to the continuing prevalence of M-type 12 strains among nephritogenic streptococci primarily associated with respiratory infections in temperate zones. These observations suggest that the skin sores commonly found on children in tropical Trinidad, provide a particularly suitable environment for development of nephritogenic types. It remains to be seen whether these types will recur or whether new types will continue to emerge in Trinidad.

Glomerular deposition of properdin in acute and chronic glomerulonephritis with hypocomplementemia

Kidney tissue from 97 patients was studied by immunofluorescent techniques using antiserum to purified properdin. All patients with acute poststreptococcal glomerulonephritis showed deposition of properdin and the third component of complement (C3), either as "humps" on the basement membrane, or in the mesangium. In all cases of chronic membranoproliferative glomerulonephritis, properdin and C3 were localized in the glomeruli, most commonly in a lobular pattern on the basement membrane. Activation of C3 by the properdin system may explain the depressed serum levels of C3 and terminal complement components even though levels of earlier components are normal, and the deposition of C3, often without immunoglobulins, in the kidneys of patients with acute glomerulonephritis or chronic membranoproliferative glomerulonephritis.

The influence of the site of infection on the immune response to group A streptococci

The immune response after streptococcal infection of the skin and of the upper respiratory tract (URT) was studied prospectively in a group of normal children, ages 3-6 yr. The children were examined and cultures for group A streptococci were obtained weekly from the throat, nose, and skin lesions (when present). Paired sera were collected at the beginning and end of the study, and the changes in antibody titers were measured for three different streptococcal antigens: streptolysin O, deoxyribonuclease B (DNAse B), and nicotinamide adenine dinucleotidase (NADase). The findings suggest that in contrast to infection of the URT antibody response to streptolysin O is relatively feeble after streptococcal infection which is limited to the skin. The response to NADase is also poor after cutaneous infection. Antibody responses to DNAse B are generally good regardless of the site of the infection. These and other studies indicate that anti-DNAse B is the antibody of choice in studying streptococcal infection of the skin and its complications.