A fibril-specific, conformation-dependent antibody recognizes a subset of Aβ plaques in Alzheimer disease, Down syndrome and Tg2576 transgenic mouse brain

Beta-amyloid (Aβ) is thought to be a key contributor to the pathogenesis of Alzheimer disease (AD) in the general population and in adults with Down syndrome (DS). Different assembly states of Aβ have been identified that may be neurotoxic. Aβ oligomers can assemble into soluble prefibrillar oligomers, soluble fibrillar oligomers and insoluble fibrils. Using a novel antibody, OC, recognizing fibrils and soluble fibrillar oligomers, we characterized fibrillar Aβ deposits in AD and DS cases. We further compared human specimens to those obtained from the Tg2576 mouse model of AD. Our results show that accumulation of fibrillar immunoreactivity is significantly increased in AD relative to nondemented aged subjects and those with select cognitive impairments (p < 0.0001). Further, there was a significant correlation between the extent of frontal cortex fibrillar deposit accumulation and dementia severity (MMSE r = −0.72). In DS, we observe an early age of onset and age-dependent accumulation of fibrillar OC immunoreactivity with little pathology in similarly aged non-DS individuals. Tg2576 mice show fibrillar accumulation that can be detected as young as 6 months. Interestingly, fibril-specific immunoreactivity was observed in diffuse, thioflavine S-negative Aβ deposits in addition to more mature neuritic plaques. These results suggest that fibrillar deposits are associated with disease in both AD and in adults with DS and their distribution within early Aβ pathology associated with diffuse plaques and correlation with MMSE suggest that these deposits may not be as benign as previously thought

The heritability and genetics of complement C3 expression in UK SLE families.

As the central component of the complement system, C3 has sensory and effector functions bridging innate and adaptive immunity. It is plausible that common genetic variation at C3 determines either serum C3 level or susceptibility to systemic lupus erythematosus (SLE), but only a single, Japanese, study has currently showed genetic association. In a cohort of 1371 individuals from 393 UK white European SLE families, we quantified serum C3 and genotyped C3 tagSNPs. Using a Bayesian variance components model, we estimated 39.6% serum C3 heritability. Genotype/serum C3 association was determined by mixed linear models. Single nucleotide polymorphism (SNP) rs344555, located in a haplotype block incorporating the 3' end of C3, was associated with serum C3 (P=0.007), with weaker associations observed for other SNPs in this block. In an extended cohort of 585 SLE families the association between C3 variants and SLE was assessed by transmission disequilibrium test. SNP rs3745568 was associated with SLE (P=0.0046), but not with serum C3. Our disease associated SNP differs from that highlighted in the Japanese study; however, we replicate their finding that genetic variants at the 3' end of C3 are associated with serum C3. Larger studies and further fine mapping will be required to definitively identify functional variants