Deficiencies of early components of the classical complement pathway, particularly C1q, are strongly associated with susceptibility to systemic lupus erythematosus. Recent data link this predisposal to autoimmunity to an inappropriate clearance of apoptotic cells, which could lead to a loss of self-tolerance. In the present study, we demonstrate that opsonization of apoptotic cells with C1q and mannose-binding lectin allows and facilitates their uptake not only by macrophages but also by human immature dendritic cells (DCs). Both C1q and mannose-binding lectin enhance the uptake of apoptotic cells by DCs in a dose-dependent way. The uptake of C1q-opsonized apoptotic cells, but not nonopsonized apoptotic cells, by DCs stimulated the production of IL-6, IL-10, and TNF-α, without an effect on IL-12p70. We conclude that these recognition molecules of the complement system do not sequester apoptotic cells from DCs, but rather promote their uptake by immature DCs. Therefore, we propose that early complement components support safe clearance of cellular debris by facilitating phagocytosis and possibly by immunomodulatory mechanisms, thus preventing autoimmunity.

These results indicate that PTX3 is expressed and released by PTECs and that in proinflammatory conditions PTX3 production is up-regulated. Local expression of PTX3 may play a role in the innate immune response and inflammatory reactions in the kidney.

Chronic rejection is the leading cause of late renal transplant failure. Various structural lesions are observed in grafts undergoing chronic rejection including glomerular basement membrane (GBM) duplications. The well-established Fisher (F344) to Lewis (LEW) rat renal transplant model for chronic rejection was used to assess the presence and role of the humoral immune response against graft antigens during chronic rejection. LEW recipients of F344 allografts develop transplant glomerulopathy and produce IgG1 antibodies directed against F344 GBM preparations that are detectable 3 weeks after transplantation. Glomerular IgG1 deposition was observed that in vitro co-localized with a rabbit anti-rat GBM antiserum in rejecting F344 grafts; elution experiments of isolated glomeruli yielded IgG1 antibodies reactive in vitro with F344 GBM, but not LEW GBM. 1 The glomeruli may show a myriad of lesions, including chronic transplant glomerulopathy, which is characterized by duplication of the glomerular basement membrane (GBM) with interposition of electron-lucent material.2,3 Transplant glomerulopathy is observed in up to 20% of kidney grafts with CR. 4 It has been postulated that CR results from immune reactions of the recipient against yet poorly defined antigens exposed in the graft. 5 Nonimmune factors, such as hypertension or ischemia/reperfusion injury, may lead to unmasking or alteration of graft antigen(s).1 In syngeneic transplants with comparable degrees of nonimmune injury, CR does not develop within the same time span compared with allogeneic grafts, underlining the importance of immunological mechanisms.6 -8 We hypothesize that immune reactions such as antibody formation after previous damage play a role in the perpetuation of CR in renal allografts. In a mouse model of chronic cardiac graft rejection, antibodies are crucial for disease development.7 Immunoglobulin heavy chain (IGH) knockout mice that receive a cardiac allograft do not develop CR in contrast to immunoglobulin heavy chain wild-type mice.7 Moreover, transfer of posttransplantation (Tx) IgG antibodies or antigen-reactive immune serum into transplanted SCID mice results in transplant atherosclerosis. 6,8 A well-established model to study CR in renal allografts is the F344 to LEW rat model. All LEW recipients of F344 grafts develop acute rejection at approximately day 30 resulting in 50% graft loss. The surviving animals show histopathological and functional characteristics of CR from day 50. The reverse combination, ie, LEW kidneys transplanted into F344 rats all exhibit long-term surviving kidney grafts in the absence of histological abnormalities, despite early acute rejection episodes. In this model, antibody responses specific for lymph node-derived lymphocytes have been described. 9 These antibodies disappeared at 8 weeks after Tx and were described to

Cellular senescence has been suggested to play a role in the deterioration of renal graft function and has been linked to telomere shortening. We have investigated markers of cellular senescence in the F344 to LEW rat model of chronic renal transplant rejection. Syngeneic and LEW to F344 transplants were used as controls. Substantial telomere shortening was observed in all transplants, including allogeneic and syngeneic grafts from day 7 post-transplant onwards. Ischemia of native F344 kidneys was already sufficient to induce telomere shortening. It is known that shortened telomeres can activate cell cycle regulators, such as p21 and p16. Accordingly, all cases showed a transient p21 increase, with a maximum at day 7 and a sustained expression of p16. Importantly, senescence-associated ␤-galactosidase staining, a cytological marker for senescence, was only observed in tubular epithelial cells of chronically rejecting F344 allografts from day 30 post-transplantation onwards. Long-term surviving LEW allografts or syngeneic F344 grafts were negative for senescence-associated ␤-galactosidase. In conclusion, ischemia during transplantation results in telomere shortening and subsequent activation of p21 and p16, whereas senescence-associated ␤-galactosidase staining is only present in chronically rejecting kidney grafts.

Abstract. Progressive renal failure is accompanied by uncontrolled accumulation of extracellular matrix in glomeruli and tubulointerstitium, eventually resulting in glomerulosclerosis. Although glomerulosclerosis occurs secondary to various renal diseases, the fact that not all patients develop progressive glomerulosclerosis suggests that genetic factors may underlie the tendency to progress, or not to progress. Identified were two Lewis rat substrains with small genetic differences but with considerable difference in resolution of glomerulonephritis after anti-Thy-1 administration. In the Lewis/Møllegard rat strain, anti-Thy-1 glomerulonephritis spontaneously resolves within 4 wk. In contrast, Lewis/Maastricht rats develop progressive glomerulosclerosis after induction of this disease. The involvement of bone marrowderived cells and kidney cells in the development of glomerulosclerosis was determined. In the first study, exchange of bone marrow between these substrains did not affect the course of anti-Thy-1 nephritis. Lewis/Møllegard rats recovered rapidly, but Lewis/Maastricht rats showed progressive disease regardless of the genotype of the bone marrow they received. In the second study, kidneys were exchanged between the substrains. After transplantation, anti-Thy-1 nephritis was induced and glomerular damage assessed at day 21. Severe damage was observed in Lewis/Maastricht glomeruli independent of whether the kidney had been transplanted or not. Similarly, Lewis/Møllegard glomeruli, whether transplanted or not, revealed no residual histopathologic abnormalities. The inherited differences between the two substrains with regard to their insusceptibility to develop progressive glomerulosclerosis after mesangial injury are governed by genes expressed by the kidney, but not by bone marrow-derived cells.