The origin of antigenicity of pig islets is mainly N-linked sugars including sialic acid antigens, but not the alpha-Gal, and pig islets can be injured by both the classical and the alternative complement pathway in human serum.

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Since complement activation is recognized as a common response of the host defense system when an artificial medical device is applied to a patient, great effort has been devoted to studies on the interaction of the complement system with artificial materials. However, some uncertainties remain, partially because of the lack of well characterized surfaces and suitable analytic methods for study of the surface phenomena that occur on artificial materials under physiologic conditions. In this study, we employed self-assembled monolayers (SAMs) and the surface plasmon resonance (SPR) technique to study interactions of the serum complement with well characterized surfaces. Self-assembled monolayers carrying various concentrations of hydroxyl groups were prepared using 11-mercapto-1-undecanol (C11-OH) and one of n-nonanethiol, n-dodecanethiol, and n-hexadecanethiol. The amount of NHS deposition on the SAMs increased with increasing C11-OH content of the SAMs, and the amount of anti-C3b antibody immobilization formed on the NHS deposition layers increased with increasing C11-OH content of the SAMs. These results clearly demonstrate that a large amount of C3b, produced through the activation of the complement system, binds covalently to and is adsorbed by hydroxyl-group-rich surfaces. The combination of SAMs and the SPR technique is suitable for studying the interaction of the complement system with solid surfaces, and the results should give basic information needed for a rational design of biocompatible surfaces on synthetic materials.

A 14-year-old girl presented with acute glomerulonephritis. Tests revealed hypocomplementemia and elevated Antistreptolysin-O titers, and renal biopsy revealed endocapillary and mesangial proliferative glomerulonephritis with double contours of the glomerular basement membrane (GBM). Despite methylprednisolone pulse therapy and the administration of oral prednisolone, overt proteinuria and hypocomplementemia persisted. A second renal biopsy 6 months later confirmed the initial diagnosis of dense deposit disease (DDD) based on electron-dense deposits in the GBM. C3 nephritic factor (C3NeF) and a deficiency of complement factor H (CFH) were not evident. A nephritis-associated plasmin receptor (NAPlr), nephritogenic group A streptococcal antigen, and the plasmin activity by in situ zymography were been in both the first and second biopsy specimens. The patient received combined immunomodulatory therapy with prednisolone and mizoribine, and the urinary protein decreased to a mild level at 27 months after disease onset. These findings suggest that persistent glomerular NAPlr deposition may be associated with the pathogenesis of DDD in some patients without the involvement of C3NeF or CFH mutation and that DDD patients of this type may respond to immunomodulatory treatment.

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