Faculty Bibliography

The molecular basis of fibril formation in Alzheimers disease was explored by electron micrographic and x-ray diffraction analysis of a series of synthetic peptides corresponding to portions of the amino acid sequence of beta protein and that of its putative precursor. A minimum 14 residue peptide was identified that formed typical amyloid fibrils under physiological conditions. Of these 14 residues, 10 were sufficient to give an identical 4.76 A and 10.6 A diffraction pattern as that recently described for isolated neurofibrillary tangles, amyloid plaque cores and leptomeningeal amyloid fibrils

Hereditary CNS amyloid angiopathy occurring in Icelanders is the first human disorder known to be caused by deposition of cystatin C amyloid fibrils in the walls of the brain arteries leading to single or or multiple strokes with fatal outcome. One or more affected members have been verified by histological examination in 8 families containing 127 affected. These originated from the same geographic area. Abnormally low value of cystatin C found in the cerebrospinal fluid of those affected can be used to support or make diagnosis of this disease, also in asymptomatic relatives. By amino acid sequence analysis the amyloid fibrils in the patients are found to be a variant of cystatin C (gamma-trace), a major cysteine proteinase inhibitor. The variant protein has an amino acid substitution (glutamine for leucine) at position 58 in the amyloid molecule. It is postulated that a point mutation has occurred leading to production of amyloidogenic protein causing the disorder

Hereditary cerebral hemorrhage with amyloidosis in Dutch patients is an autosomal dominant form of vascular amyloidosis restricted to the leptomeninges and cerebral cortex. Clinically the disease is characterized by cerebral hemorrhages leading to an early death. Immunohistochemical studies of five patients revealed that the vascular amyloid deposits reacted intensely with an antiserum raised against a synthetic peptide homologous to the Alzheimer disease-related beta-protein. Silver stain-positive, 'senile plaque-like' structures were also labeled by the antiserum, yet these lesions lacked the dense amyloid cores present in typical plaques of Alzheimer disease. No neurofibrillary tangles were present. Amyloid fibrils were purified from the leptomeningeal vessels of one patient who clinically had no signs of dementia. The protein had a molecular weight of approximately equal to 4000 and its partial amino acid sequence to position 21 showed homology to the beta-protein of Alzheimer disease and Down syndrome. These results suggest that hereditary cerebral hemorrhage with amyloidosis of Dutch origin is pathogenetically related to Alzheimer disease and support the concept that the initial amyloid deposition in this disorder occurs in the vessel walls before damaging the brain parenchyma. Thus, deposition of beta-protein in brain tissue seems to be related to a spectrum of diseases involving vascular syndromes, progressive dementia, or both.

Evidence implicates cells belonging to the mononuclear phagocytic system (MPS) in the development of some forms of amyloidosis (10, 22). Whether or not the MPS is involved in central nervous system amyloidosis is not known. As a first step to address this issue, microglial and astroglial cells isolated from mouse brains were cultured and characterized as to the properties they may share with other members of the MPS. It was shown by light and electron microscopy that both cell types phagocytose latex particles, but that only microglial cells engulf immunoglobulin sensitized erythrocytes. By means of immunohistochemical, immunofluorescence, and immunoblotting techniques, it was established that the cells contain and secrete lysozyme as well as the proteinase inhibitor cystatin-C (-gamma trace). Cystatin-C was distributed in the cytoplasm and the nucleus and was strikingly associated with filaments and bundles of fibrils. Another enzyme, commonly used to distinguish cells belonging to the MPS, is alpha-naphthyl butyrate esterase. Shortly after their isolation, only the microglial cells were positive, but on continued culturing, increasing numbers of astroglial cells became positive for alpha-naphthyl butyrate esterase. By day 22, almost all of the cells were positive. Freshly isolated cells were negative for the monocyte-specific antigen Mac-1. However, after 4 days, cells with the morphology of microglia had become positive, whereas astroglia failed to exhibit this antigen with up to 22 days in culture. Thus, both astroglia and microglia have properties in common with cells of the MPS which may be useful for future studies. However, on fresh isolation only microglia were indistinguishable from monocytes for all features tested.

The primary structure of a 38 kDa heparin-binding domain from human plasma fibronectin has been determined. This domain contains 380 residues arranged in three type-III homology regions of approx. 90 residues each, and a 67-amino-acid C-terminal segment. This segment has been shown to be encoded by certain mRNA species only, due to alternative splicing [Kornblihtt, Vibe-Pedersen & Baralle (1984) Nucleic Acids Research 12, 5853-5868], and therefore represents a region of heterogeneity in fibronectin. Our data indicate that at least one of the constituent polypeptide chains contains this region.

The relationship between the immunoglobulin kappa light chain allotypes and autoantibodies was studied in a series of seven human monoclonal kappa-bearing IgM antibodies with Rheumatoid Factor (RF) activity, two IgM anti-low density lipoprotein (LDL) antibodies, and one IgM anti-intermediate filament (IF) antibody. Residues at amino acid positions 153 and 191 related to the Km allotypes in human kappa chains were determined by an HPLC tryptic fingerprint and corroborated by amino acid sequence analysis. All the autoantibodies shared similar variable regions derived from the V kappa IIIb gene(s). The seven RF and the anti-IF were associated with the Km(3) constant region allotype whereas the two anti-LDL were associated with the Km(1,2) allotype. Thus, monoclonal autoantibodies showed the same Km allotypic distribution as the normal population. However, although the number of samples is small, it seems likely that a preferential association may exist between particular V kappa genes and Km alleles in the generation of autoantibodies with different specificities

The amino acid sequence of the L-CDR2 (complementarity-determining region) of Bla mRF (monoclonal rheumatoid factor) is identical to that of the Wa mRFs. The PSL2-CRI (crossreactive idiotype), as determined by anti-PSL2, which has been shown to be present on all Wa mRFs, is also present on the Bla mRF and other monoclonal autoantibodies. PSL2-CRI is, therefore, not unique to Wa mRFs and may be present on most IgM kappa monoclonal autoantibodies. Whether PSL2-CRI is a crossidiotype (XId) that is selectively present on autoantibodies or represents an allotypic marker for a V kappa III gene is undetermined.