A REVIEW OF GLOMERULAR ULTRASTRUCTURE IN SYSTEMIC LUPUS ERYTHEMATOSUS Francis R. Comedord D e p a ~ m e n t o f E x p e r i m e n t a l M e d ~ e , Universi~ College, Go/way. A classification of glomerular lesions Introduction ENAL involvement is a major com- in SLE R p o n e n t of the mudisystem disease, Between 1957 and 1966, a number of systemic lupus erythematosus (SLE). It papers, reviewed by Comerford and occurs in over haft the patients with the Cohen (1967), described a spectrum of disease and is a common cause of death ultrastructural abnormalities in renal (Estes and Christian, 1971). In spite of biopsies from patients with SLE. ~hese much investigative effort over the past included epithelial cell abnormalities, 25 years, the optimal management of dense deposits in relatiorf to the capillupus r~ephritis has not yet ~eest est- lary wall and mesangium, thickening and ablished (Wagner, 1976). In part, this perforation of the basement membrane, uncertainty may be due to problems in endothelial and mesangial proliferation calegorizing the morphology of the renal and apparent phagocytosis of dense lesions, leading in turn to difficulties in material by endettlegal cytoplasm, Based attributing prognostic significance to on eleclron microscopic studies of kidspecific findings. ney biopsies from 13 patients with SL.E. The evaluation of possible renal dis- Comerford and Cohen (1967) proposed ease in a patient suffering from SLE may a classification of glomerular abnormalinvolve the measurement of several dif- itJes. Lesions were assigned to one of ferent indices, immunologic abnormality three groups according to the type of may be represented by raised blood involvement of the l)eripherel glome'rular levels of antibodies to specific nuclear capillary wall (i.e. the free portion of the constituents and by decreased blood e~pigary wall, excluding the mesangJal levels of complement components. Renal and juxtamesangia] regions). The classifunct)onal abnormalities may include fication is illustrated in diagrammatic proteinuria, haematuria, cylindruria, dis- form in Figure f. ordered blood chemistry and abnormal Group 1 SLE Glomeru/ar Lesions, Fig. clearance vahzes. The study of kidney biopsy specimens by light microscopic, 2. No dense deposits in relation to electron microscopic and immunofluor- the glomeru/ar peripheral capillary wall. escent techniques permits evaluation of Abnormalities found were epithelial foot the morphology and irnmunopathology process fusion and rnicrovgli, variable nodularity and thickening of the periphof the lesion. eral basement membrane, endotherial From these considers'lions, it will be and mesang~al proliTeradon and occasapparent that the topic discussed in this ional mesangial dense deposits. review, uitrastructural glomerular abnormalities, represents only one limited Group II SLE Glomerular Lesions. area in the delineation of renal involve- Figs. 3 and 4. Subepithelial or intramemment in SLE. There is an obvious need, branous dense deposits in relation to however, to determine the value and the glomerular peripheral capillary wall. utility of each individual investigative NO subendothelial dense deposits. technique. There were areas of fusion of epithelial

Fig. i--Diagrammatic representation of the peripheral glemerular ca~3illary loop in SLE The basement membrane ( B M ) is represenLed, in e•ch diagram by the eentra~ gray band wilh 8pilhelium to the left and el]ale'.helium to the Tighi. Dense deposits ate shown in black. Group 1 lesions may show nodu]al or unilerm thickening of 1he B M and the~e are no dense deposits in relation to the perlpheral capilJary wall. Group II Jesions are characterized by the presence of subepithellal or intramembranous dense deposits. Group I[I les~ons show subendethellal dense deposits. See text for full description cell foot p r o c e s s e s - - o f t e n three or more micrornetres in extent. Dense deposits were present on the epithelial aspect of the basement m e m b r a n e (Fig. 3) or within it (Fig 4). T h e b a s e m e n l membrane itself was olten t h i c k e n e d in a u n i f o r m or irregular m a n n e r and findings resembling m e m b r a n o u s glomerulonephritis were seen in some specimens. Endothelial ce!l proliferation was variable. Mesangial abnormalities included proliferation of cells and matrix, dense deposits and the presence of c o l l a g e n

Group fit SLE G/omerular Lesions, Dense deposits in. an immedialely subendethelial location in relation to the glomerular peripheral capillary w a l l Epithe]ial cell abnormal-

Figs, 5 a n d 6

tries were focal foot process fusion, microvilli and dense cytoplasmic i n c l u s i o n s In g e n e r a ] , the basement m e m b r a n e showed less t h i c k e n i n g and nodularity than in G r o u p II lesions. Subepithel~al dense deposits tended to be discrete, Subendothelial dense deposits were immediately adjacent to the inner aspect of the basement m e m b r a n e and varied in size, density and texture. Reticulation of the endothelial cytoplasm was often prominent, and aggregates of dense material were sometimes seen within the endothelial cytoplasm, at t h e cell s u p face partially surrounded by rnicrovini and free in the capillary lumen. Mesangial deposits were often extensive.

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Fig. 2--Group I SLE lesion. A capillary loop is partiaJly occluded by endothelial cerls and the adjacent mesangial region has small dense deposits. CL, capillary lumen; M, mesangial region; EP, epithelial cytoplasm. X 14,000.

Fig. 3--Group rl SLE lesion, Part ef the peripheral g]omerular capillary wall with partial fusion ef epithelial cell,foot processes and several small subepithelia[ dense deposits (one indicated by arrow). CL, capillary lumen; US, urinary space. X 27,000,

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Fig. 4 Group II SLE lesion. Nigh magnification view of the periprleral glomerular capillary wall ~ilh an ,ntramembranousdense deposit (arrow) and nodularity Of the basement membrane9 CL, cap,llary lumen: US, urinary space X 110.000 This is a cumulative classdicahor~t thus Group III lesions may 8how teatures of Grou~ II lesions such as subepithelial dense deposits and Group II lesions may have features of Group I lesions. The correlation of ultrastructural abnormalities with clinical renal disease may be summarized as follows. Patients with Group I lesions have only minor clinical abnormalities Patients wgh Group II I~slons will have variable clinical abnorm3hdes, Patients with Group ill lesions will usually have significant clinical abnormalities, (There are exceptions and Hecbt et al. (1976) have described pahents with Group III lesions and no clinical renal abnormalities) Other workers have described similar correlations (Duioune et al., 1972: Grishman et af.. 1973: Sinniah and Fang, 1976), Glomerular involvement in SLE may

be local and, in con~padson with light microscopy, only a limited sample is examined by electron-microscopy. A minimum of three glomeruli from each specimen were examined in the studies on which the classification was based and in a more recenl study by other investigators {Dillard et al., 1975), Whether this is an adequate sample in all cases remains to be established, Only three groups ol ul~rastructurai abnorma]iges are utilized in this classilication and it is possible that differences b~tween findings within a single group may be significanl. For example, do the Group II lesions illustrated in Fig. 3 and Fig. 4 represent different stages In the pathological process ? If so, then their presence may have different prognostic implications. Similarly, the presence or absence of apparent enctothe]ia] phagocytosis of dense aggregates in Group III lesions may be

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}mportant. Certain investigators have made semiquantitative estimates of the size of dense deposits (Shelp et el., 1971; Grishman et el., 1973; Ginzler et al., 1974), and Dillard et el. (1975) suggest that large subendothelial deposits are associated with more severe disease. The classification of light microscopic findings in lupus nephritis is difficult and different methods have been utilised by various workers. The correlation of light microscopic and electron microscopic findin(js wgI not be exact because of the differences between the two techniques; Hayslett et el. (1972) presented an acceptable comparison between the ultrastructural classification discussed in this review and certain light microscopic classifications of lupus nephritis.

Theevolutionoftheglomerular|eslon in SLE

The evolution of the glomerular lesion in SLE is of importance in relation to prognosis and to concepts 01 pathogenesis. Ultrastructurai studies have contribu, ted to our understanding of these processes. It was suggesled (Comerford and Cohen, 1967) because of certain morpholeglcal findings, that Group II and pe~'haps some GroL~p t Iesions might result from the resolution of acute Group Ill lesions, Alternatively, the three types of resion might occur independently as a consequence of variabre involvement by a single pathogenic process or due to three separate iniurious processes.

to ,I

I,

Fig. 5--Group Ill SLE lesion. A glomerula[ caplrlary loop and mesangial area lhe capillary [s hoed with ex[en~,ve subenoothelialdense deposils 8n0 there a r e large mesanglaJdupes its. Thus find,rigs a,e lhe UllfaSlruotural equlvalenl of I n e {ignJ microscopic "wlre-loop". CL. capillary leUmen: M mesangial region; US, ,uri~ew space. X 15000.

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Fig ~--Groop III SLE lesion. The subendothelial dense deposit may be dlstingulshed from the basement membrane and is several times thicker. Epit~el,al foot processes are well preserved A tubuleret,cular structure (arrow) is present in endothelial cytoplasm. CL, ca#illary lumen; D. subendotbelial dense deposit; BM. capillary basemen~ mem~3rane;EP. epit~el,al cell toot process. 75.000 X An animal model of SLE, New Zealand Black {NZB) mouse disease is characterized by immunologic abnormal;lies which include antlnuclear antibodies and positive lupus erythematosus cell tesls, autoimmune haernolytic anaemia and nephritis (Heyler and Howie, 1963). The palhogenesis of the nephritis is similar to that of human lupus nephritis (Lambert and Dixon, 1968). Electron microscopic sludie~ of the evolution of the glomerular lesion in NZ8 mouse disease (Comerford et ah, 1968; Comerford and Cohen, 1971a) revealed a sequential process represented in diagramatio form in Fig. 7. Mesangial deposits were present in some animals at 12 weeks of age and in all at 24 weeks. Subendothel[al dense deposits occurred only in older animals at 32 to 52 weeks of age. These findings suggested that a given injurious process might be expressed in di#erent patterns of glomerular

pathology at different times during its evolution. Recent studies of human Iupus ttephri6s have provided further information. Hecht et al. (1976) described the progression of Group III lesions to Group 11 and Group I lesions in some patients, when biopsy was repeated one to two years after treatment with azathioprine and low doses of prednisone. This dissolution of subendothelial dense deposits had favourable prognostic impliCalions. Baldwin et al, (9177) presented data on a large series of patients whose renal lesions were categorized primarily by light microscopic criteria (Baldwin et al., 1970). They suggested that in two OUt of every thre3 patients with 8LE, renal disease develops early in the course of the disease and thal the particular variety occuring tends to persisl in a given patient They also noted variable glomerular sclerosis in the different

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Tubulot'etlcular s|tuctutes and organized dense deposits in lupus nephr Gyorkey et al. (1969) described struc~ tures resembling myxovirus in the glom* erular endotheliurn of kidney biopsies from patients with SLE. Other workers confirmed these findings (Norton, 1969; Hurd e t af., 1969; Bloodwotth and Shelp, 1970, etc.). One such structure is visible in Fig. 6, with the usual appearance of intertwined tubules, measuring 20 to 25 nanometres in diameter. Further studies have shown that the presence of these structures [s no specific for SLE and they may be found in unrelated kidney diseases and in other cells and tissues, Nor have efforts to con|i[m the viral nature of the structures been successful. Garancis et al. (197!) noted a 20 per cent incidence of the structures in patients with kidney disease other than lupus nephritis but concruded that the presence of many large clusters in glomerular endothegum was of significance in the diagnosis of SLE.

Fig. 7--Diagrammatic representation of the major abnormalities in NZB nephritis. A, epilhelial nodules. B, mesangiaf dense deposits present in some animals at 12 wee~s ot age and in all at 24 weeks. C, supepitheiial dense deposits, first seen in 24 week mice D, subendethelial dense deposits, seen on~y in 32 and 52 week animals. EP, epJthelJar toot processes; EN, endolhelial cerr; Grishman et al. (1967) described an CL, capillary lumen; BM. peripheral basement uncommon variety of glemerular pathmembrane; MEg, mesangial region. ology in lupus nephritis. Dense deposits, in contrast to the usual finely granular types of lupus nephritis and, in some appearance, had an organized pattern patients, an increassd percentage of of alternating dark and light parallel bands. Comerfo[d and Cohen (197fb, sclerotic glomeruli wifh time. 1971c) found similar and equally rare A progression from minor {o more deposits in NZB nephritis. severe renal involvement is thought to be uncommon after the first year of SLE, but has been documented in a minority Conclusions of patients (Ginzler et af., 1974; ZimOver the past 26 years, a series of merman et al., 1975). studies has been of value in delineating In summary, these studies suggest that ultrastructural findings in the renal lesa progression or evolution of glemerular ions of systemic lupus erythematosus, lesions in SLE is readily detected at an More recentry, increasing attention has ultrastructural level but is less apparent been directed at the evolution of the by light microscopy. In NZB nephritis, lesions and their clinicopathologic imthere is a relenf~ess progression of renal p{ications. pathologic changes with age. The more variable findings in human SLE may reIlect an intermittent activity of injurious processes over a longer period of time,

Any form of crinical investigation must be evaluated in terms of its utility in providing information ol prognostic value.

Fig. 8--Large mesangial dense deposits in a 24 week old NZ8 mouse. CL, capillary lumen; ~, mesang{a~ region; EP. epl)hemial cytoplasm. X 7,OgO, T h e r e is e v i d e n c e t h a t t h e c l a s s i f i c a t i o n of g l o m e r u l a r a b n o r m a l i t i e s in S L E discussed in t h i s r e v i e w m a y b e of clinical value Figures 1, 4 and 5 reproduced from Comer, ford, F, P. and Cohen, A S. "The Nephropathy of Systemic Lupus E~ylhematosis" Medicine (Baltimore) 46 : 425, 1967 with the permission of the copyright holders, the Williams and Wilkins Company Figures 7 and 8 are reproduced from Comen'ord. F R., Cohen, A. S. and DesaL R. G. "The Evolution of the GIomeruIar Lesion in NZB mice', Laboratory Investigation 19: B43, 1988 with Ihs permission ef the copyright holders, 1he United States-Canadian Division of the International Academy of Pathology, Figures 1 and 7 were drawn originally by Mr. David Feigenbaum and Figure 1 was modiEed by Mr. M~ehae[ Kelly,

Re~e~e~r

Baldwin D. S., Lowensteln, J, Rothfield, N F, G~IIIO, G, and McClusky, R. T. 1970. The clinical course of the proliferative and membranous forms of lupus nephrB[s Ann, Inl. Med. 7~}, 929.

Baldwin, D. S, Gluck, M. C.. LowensteJn, J and Gallo, Gtoria R 1977. Lupus nephritis: Clinical course as related to morpholegic forms and their transition. A m J. Med, 62, 12 B(oodworth, J. M B. d t and She[p, w. D 1970 Endothelial cytoplasmic inclusions Arch, Path, s 25Z Comerford, F R., Cohen, A. S 1967. The nephropathy of systemic lupus erythematosus. An assessment by cl;n[eal, light and electron microscopic criteria. Medicine ( a a l t ) 47, 425. Comerford, F R., Cohen, A S, and Desai, R. G. 1988, The evolution of the glomerular lesion in NZB mice Lab. Invest. 19, 643, Comerford, F, P. and Cohen, A S. 1971a. Fine structure of the kidney in NZB meuse disease. Prec. Conf. on atypical virus infections. Ed. C. L. Christian. Arthritis Foundation, p. 80, Comerford, F, R. and Cohen, A, S, 1971b. Two hitherto undescrlbed intraglomeruJar deposits in NZB mouse disease Arthritis Rheum. 14 155. Comerford, F R and Cohen. A. S. 1971c. Organized intraglomerular deposits ~n NZB mouse disease. 2gth Ann. Prec. Electron Microscopy Soc A m e r p 544.

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Dillard, M, G., Tillman, R, L, and Samson, C. C, 1975. Lupus nephritis. Correlations between the cJinical course and presence of e i ~ t r o n dense deposits. Lab. ~nvest. 32, 261. Suiovne, I., Porlak, M, E., Piranl, C. L. and Diliard, M. G. 1972. The distribution and character o1 glomerular deposits in systemic lupus erythematosus. Kid. Internat, 2, 33. Estes, D. and Chdstianr C, L. 1971. The natural history of systemic lupus erythem~tosus by prospecbve analysis. Medicine (Bait.) 50, 85, Garancis, J. C., Kemorowski, R. A,, Bernhard, G. C. and 9tralimfjord, J. V. 1971. Significance of cytoplasmic microtubules in lupus nephritis. Am. J, Path. 64, 1. Ginz~er, E. M., Nicaetri, A. D., Chen, C. K., Friedman, E, A., Diamond, H. S. and Kaplan, D. 1974. Progression o1 mesangial and focal to diffuse lupus nephritis. New Eng. J. Mad. 291, 693. Grishman, E., Porush, J, C., Rosen, S. M. and Churg, J. 1967. Lupus nephritis with organised deposits in the kidneys. Lab. Invest. 16, 717. Grishman, E,, Porush, J. G., Lee, S. L. and Churg, J. 1973. Renal biopsies in lupus nephritis. Correlation of electron microscopic findings with clinical aourse. Nephron. 16, 25. Gyorkey, F., Min, K. W., SFncovic, J G. and Gyorkey, P. 1969. Systemic lupus erythematosus and myxcvirus, New Eng. J. Med. 280, 333. Hayslett, J. P., Kashgarian, M., Cook, C. D. and Spargo, S H. 1972. The effect of azathieprine on lupus glomerulonephr(3is Medicine (Bait.) 51, 393.

Hecht, B., SJegal, N., Adler, M., Kashgarian, M. and Hayslett, J. D. 1976. Prognostic indices in lupus nephritis Medicine ((3a(3.) 55, 163. Helyer, (3. J. and Howie, J. (3, 1963. Renal di~ ease associated With positive lupus erythematosus tests in a cross bred strain of mice. Nature 197, 197. Hurd, (3. R., Eigenbrodt, E., Ziff, M. and Strunk, S. W. 1969. Cytoplasmic tubular structures in kidney biopsies in SLE. Arthritis Rheum, 12, 541. Lambert, P. H., Dixon, F, d, 1968, Pathegenesis of the elomerulonephritis of NZB/W mice. J. Exp. Mad. 74, 369. Norton, W. I. 1969. Endothelial inc[usion~ in active lesions of SLE. Journal Lab. Clin, Mad. 74, 369. SheJp, W. D,, Bloodworth, J. M. S. and RieSelbach, R. E, 1971 Effect of azathioprine on renal histology and function in" lupus nephritis. Arch Int. Med. 125, 566. Sinniah, R. and Fang, P. H, 1976. Lupus nephritis: correlation between light, electron microscopic and immunofluerescence findings and renal function. Clin. Neph, 6, 340. Wagner, L, 1976 Immunosuppress/ve agents in lupus nephritis: A cStica] analysis, Medicine (BalL} 55, 239. ZJmmerman, S. W., Jenkins, P, G., SheJp, W. D., Bloodworth, J, M. B. Jr., (3urhholder, P. M. 1975. Progression from minimal or focal to diffuse proliferative lupus nephritis. Lab. Invest, 32, 666