Defective immunoglobulin A (IgA) glycosylation and IgA deposits in patients with IgA nephropathy.

Defective glycosylation and immune complex (IC) formation may be of primary importance in immunoglobulin A nephropathy (IgAN) pathogenesis. The aim of this study was to determine whether defective IgA1 glycosylation might support renal deposition of IgA and disease activity. IgA was isolated from the serum of 44 IgAN patients and 46 controls and glycosylation analysed by ELISA using glycan-specific lectins. IgA was measured by immunodiffusion and immune complexes by ELISA. IgA subclasses in IC deposits in kidney glomeruli were identified by immunohistochemical methods. A significant increase in N-acetylgalactosamine (GalNAc) in terminal position (p = 0.02) observed in some of the IgAN patients, became more pronounced when sialic acid was removed from IgA1, indicating enhanced expression of α-2,6-sialyltransferase in patients compared with controls (p < 0.0001). Patients with defective galactosylation had lower serum IgA than other IgAN patients (p = 0.003). IgAN patients with both IgA1 and IgA2 glomerular deposits (21.7%) had increased GalNAc in terminal position (p = 0.003). Taken together, our results show that increased IgA glycosylation in IgAN associates with low levels of IgA, concomitant IgA1 and IgA2 glomerular deposits and poor clinical outcome.

Low complement C4B gene copy number predicts short-term mortality after acute myocardial infarction.

BACKGROUND AND OBJECTIVES: Some recent data indicate that risk of death after acute coronary syndrome is under genetic control. Previously, we found that the C4B*Q0 genotype (low copy number of the C4B gene that encodes the fourth component of complement) is strongly associated with morbidity and mortality of cardiovascular diseases (CVD). The +252 G allele of the lymphotoxin-alpha (LTA) gene encoded close to the C4B gene was also reported to be related to CVD-related mortality in an Oriental population. METHODS: The relationship between the copy number of the genes encoding the fourth component of complement (C4A and C4B) and LTA 252 single-nucleotide polymorphism (SNP) on the one hand and mortality after acute myocardial infarction (AMI) was studied in 142 Icelandic patients. The number of the C4A and C4B genes was determined in genomic DNA samples by a newly developed real-time PCR-based method; lymphotoxin-alpha (LTA) +252 A>G polymorphism was determined by PCR-restriction fragment length polymorphism analysis. RESULTS: The C4B*Q0 genotype was found to be strongly associated with 1-year mortality, with a hazard ratio of 3.50 (1.38-8.87) (P = 0.008) (adjusted Cox regression analysis). This association was, however, restricted to ever-smoking patients. By contrast, neither C4A gene copy numbers nor LTA 252 SNP did confer increased risk of mortality after AMI. CONCLUSIONS: This observation indicates that low C4B copy number is a strong risk factor for short-term mortality after AMI in smoking Icelandic patients, whereas LTA 252 G allele is not a risk factor in Caucasian population.

Vaccinia virus complement control protein diminishes formation of atherosclerotic lesions: complement is centrally involved in atherosclerotic disease.

Complement is known to be activated in atherosclerotic lesions, but the importance of this event in disease pathology is a matter of debate. Studies of rabbits fed a high-fat diet have indicated complement activation as a rate-limiting step, whereas results from genetically modified mouse strains (ApoE-/- or LDLR-/-) have failed to support this finding. To resolve whether this reflects differences between species or between genetically driven and diet-induced disease, we studied the effect of a complement inhibitor, vaccinia virus complement control protein (VCP), on C57BL/6 mice, the background strain of ApoE-/- and LDLR-/- mice. Atherosclerosis was induced by a high-fat diet, and VCP (20 mg/kg) was injected once per week after the eighth week. Fatty streak development was monitored at 15 weeks by microscopic examination of oil red-O-stained sections from the root of the aorta. VCP injections led to significant (50%) reduction of lesion size (P = 0.004). Lesions were marked by gradual accumulation of lipids and macrophages but did not develop beyond the fatty streak stage. VCP activity disappeared from serum in 4 days, and the possibility therefore exists that a higher level of protection may be achieved by more frequent injections. We conclude that the development of fatty streaks in diet-induced atherosclerotic disease can be significantly retarded by prophylactic treatment with a complement inhibitor. These results support previous findings from complement-deficient rabbits and suggest that the pathogenesis of atherosclerosis in diet-induced disease differs from that induced by major defects in lipid metabolism.