Aluminum-induced generation of lipopolysaccharide (LPS) from the human gastrointestinal (GI)-tract microbiome-resident Bacteroides fragilis

Gram-negative bacteria of the human gastrointestinal (GI) tract microbiome: (i) are capable of generating a broad-spectrum of highly neurotoxic, pro-inflammatory and potentially pathogenic molecules; and (ii) these include a highly immunogenic class of amphipathic surface glycolipids known as lipopolysaccharide (LPS). Bacteroides fragilis (B. fragilis), a commensal, Gram negative, non-motile, non-spore forming obligatory anaerobic bacillus, and one of the most abundant bacteria found in the human GI tract, produces a particularly pro-inflammatory and neurotoxic LPS (BF-LPS). BF-LPS: (i) is known to be secreted from the B. fragilis outer membrane into the external-medium; (ii) can damage biophysiological barriers via cleavage of zonula adherens cell-cell adhesion proteins, thereby disrupting both the GI-tract barrier and the blood-brain barrier (BBB); (iii) is able to transit GI-tract barriers into the systemic circulation and cross the BBB into the human CNS; and (iv) accumulates within CNS neurons in neurodegenerative disorders such as Alzheimer's disease (AD). This short communication provides evidence that the incubation of B. fragilis with aluminum sulfate [Al₂(SO₄)₃] is a potent inducer of BF-LPS. The results suggest for the first time that the pro-inflammatory properties of aluminum may not only be propagated by aluminum itself, but by a stimulation in the production of microbiome-derived BF-LPS and other pro-inflammatory pathogenic microbial products normally secreted from human GI-tract-resident microorganisms.

Early insight into the potential contribution of aluminum to neurodegeneration - A tribute to the research work of Robert D. Terry, Igor Klatzo, Henryk M. Wisniewski and Donald R.C. Mclachlan

The first successful attempt to obtain purified aluminum metal was accomplished by the Danish physicist and chemist Hans Christian Orsted in 1824, however it was not until about ~140 years later that aluminum's capacity for neurological disruption and neurotoxicity was convincingly established. The earliest evidence of the possible involvement of this biosphere-rich metallotoxin in Alzheimer's disease (AD) originated in the early-to-mid-1960's from animal and human research investigations that arose almost simultaneously from independent laboratories in the United States and Canada. This short communication pays tribute to the pioneering research work on aluminum in susceptible species, in AD animal models and in AD patients by the early investigators Drs. Robert D. Terry, Igor Klatzo and Henryk M. Wisniewski with special acknowledgement to the late Dr. Donald RC McLachlan, and their contemporary physician-scientist colleagues and collaborators. Together these researchers established the groundwork and foundation towards our understanding of the potential contribution of aluminum to progressive, age-related and lethal neurodegenerative diseases of the human central nervous system.

Chromosome 21-Encoded microRNAs (mRNAs): Impact on Down's Syndrome and Trisomy-21 Linked Disease

Down's syndrome (DS; also known as trisomy 21; T21) is caused by a triplication of all or part of human chromosome 21 (chr21). DS is the most common genetic cause of intellectual disability attributable to a naturally-occurring imbalance in gene dosage. DS incurs huge medical, healthcare, and socioeconomic costs, and there are as yet no effective treatments for this incapacitating human neurogenetic disorder. There is a remarkably wide variability in the 'phenotypic spectrum' associated with DS; the progression of symptoms and the age of DS onset fluctuate, and there is further variability in the biophysical nature of the chr21 duplication. Besides the cognitive disruptions and dementia in DS patients other serious health problems such as atherosclerosis, altered lipogenesis, Alzheimer's disease, amyotrophic lateral sclerosis (Lou Gehrig's disease), autoimmune disease, various cancers including lymphoma, leukemia, glioma and glioblastoma, status epilepticus, congenital heart disease, hypotonia, manic depression, prostate cancer, Usher syndrome, motor disorders, Hirschsprung disease, and various physical anomalies such as early aging occur at elevated frequencies, and all are part of the DS 'phenotypic spectrum.' This communication will review the genetic link between these fore-mentioned diseases and a small group of just five stress-associated microRNAs (miRNAs)-that include let-7c, miRNA-99a, miRNA-125b, miRNA-155, and miRNA-802-encoded and clustered on the long arm of human chr21 and spanning the chr21q21.1-chr21q21.3 region.

The sweet thing about Type 1 diabetes: A cryoprotective evolutionary adaptation

The reasons for the uneven worldwide distribution of Type 1 diabetes mellitus have yet to be fully explained. Epidemiological studies have shown a higher prevalence of Type 1 diabetes in northern Europe, particularly in Scandinavian countries, and Sardinia. Recent animal research has uncovered the importance of the generation of elevated levels of glucose, glycerol and other sugar derivatives as a physiological means for cold adaptation. High concentrations of these substances depress the freezing point of body fluids and prevent the formation of ice crystals in cells through supercooling, thus acting as a cryoprotectant or antifreeze for vital organs as well as in their muscle tissue. In this paper, we hypothesize that factors predisposing to elevated levels of glucose, glycerol and other sugar derivatives may have been selected for, in part, as adaptive measures in exceedingly cold climates. This cryoprotective adaptation would have protected ancestral northern Europeans from the effects of suddenly increasingly colder climates, such as those believed to have arisen around 14,000 years ago and culminating in the Younger Dryas. When life expectancy was short, factors predisposing to Type 1 diabetes provided a survival advantage. However, deleterious consequences of this condition have become significant only in more modern times, as life expectancy has increased, thus outweighing their protective value. Examples of evolutionary adaptations conferring selection advantages against human pathogens that result in deleterious effects have been previously reported as epidemic pathogenic selection (EPS). Such proposed examples include the cystic fibrosis mutations in the CFTR gene bestowing resistance to Salmonella typhi and hemochromatosis mutations conferring protection against iron-seeking intracellular pathogens. This paper is one of the first accounts of a metabolic disorder providing a selection advantage not against a pathogenic stressor alone, but rather against a climatic change. We thus believe that the concept of EPS should now include environmental factors that may be nonorganismal in nature. In so doing we propose that factors resulting in Type 1 diabetes be considered a result of environmental pathogenic selection (EnPS).

Are hereditary hemochromatosis mutations involved in Alzheimer disease?

Mutations in the class I-like major histocompatibility complex gene called HFE are associated with hereditary hemochromatosis (HHC), a disorder of excessive iron uptake. We screened DNA samples from patients with familial Alzheimer disease (FAD) (n = 26), adults with Down syndrome (DS) (n = 50), and older (n = 41) and younger (n = 52) healthy normal individuals, for two HHC point mutations-C282Y and H63D. Because the apolipoprotein E (ApoE) E4 allele is a risk factor for AD and possibly also for dementia of the AD type in DS, DNA samples were also ApoE genotyped. Chi-squared analyses were interpreted at the 0.05 level of significance without Bonferroni corrections. In the pooled healthy normal individuals, C282Y was negatively associated with ApoE E4, an effect also apparent in individuals with DS but not with FAD. Relative to older normals, ApoE E4 was overrepresented in both males and females with FAD, consistent with ApoE E4 being a risk factor for AD; HFE mutations were overrepresented in males and underrepresented in females with FAD. Strong gender effects on the distribution of HFE mutations were apparent in comparisons among ApoE E4 negative individuals in the FAD and healthy normal groups (P < 0.002). Our findings are consistent with the proposition that among ApoE E4 negative individuals HFE mutations are predisposing to FAD in males but are somewhat protective in females. Further, ApoE E4 effects in our FAD group are strongest in females lacking HFE mutations. Relative to younger normals there was a tendency for ApoE E4 and H63D to be overrepresented in males and underrepresented in females with DS. The possibility that HFE mutations are important new genetic risk factors for AD should be pursued further.

Search for a Caenorhabditis elegans FMR1 homologue: identification of a new putative RNA-binding protein (PRP-1) that hybridizes to the mouse FMR1 double K homology domain

A mixed stage lambdagt10 Caenorhabditis elegans cDNA library was screened with a probe derived by polymerase chain reaction from the double K homology (KH) domain of mouse FMR1 cDNA, a region that is highly conserved in the human, mouse, chicken, and frog FMR1 proteins. Four positively hybridizing cDNAs were cloned and characterized by sequencing. The overlapping sequences map to cosmid R119 from C. elegans linkage group (chromosome) I, and encode a novel proline-, polyglutamine-, and RGG box-rich putative RNA-binding protein. While the cDNA has two regions with similarity to the mouse double KH domain probe at the nucleotide level, there is no significant similarity of the amino acid sequence with human FMR1, FXR1 or FXR2, nor with KH amino acid motifs. The R119 protein, therefore, does not represent an FMR1 homologue.

Iron metabolism and human ferritin heavy chain cDNA from adult brain with an elongated untranslated region: new findings and insights

Ferritin is a ubiquitous protein which plays a major role in iron sequestration, detoxification and storage. In this paper we highlight the role of ferritin in iron homeostasis and describe factors and diseases that affect its expression. We also describe new studies which further characterize the structure and expression of a novel form of ferritin heavy (H) chain mRNA that was identified in brain and discuss possible implications of these findings. Human fetal and adult brain cDNA libraries previously were screened with cDNA for well-characterized liver ferritin H. In addition to 'liver-like' brain ferritin H cDNA, novel ferritin H cDNAs with an additional 279 nucleotide sequence at the 3'untranslated region (UTR) were identified in both libraries (see refs. 1 and 2; Dhar, M., Chauthaiwale, V., and Joshi, J. G., Gene, 1993, 126, 275 and Dhar, M., and Joshi, J. G., J. Neurochem., 1993, 61, 2140). However, relative to liver ferritin H cDNA, these novel cDNAs were incomplete at their 5'ends [see ref. 3; Joshi, J. G., Fleming, J. T., Dhar, M. S., and Chauthaiwale, V., J. Neurol Sci., 1995, 134, (Suppl.), 52]. In the present paper, by sequencing of cDNAs using reverse transcriptase polymerase chain reaction, we show that the 279 nt 3'UTR sequence, a coding sequence identical to that in human liver ferritin H, and a full-length 5'UTR that includes one mRNA regulatory iron-response element sequence, co-exist in at least one species of ferritin H transcript in six normal human adult and six late-onset, sporadic Alzheimer disease (AD) brains. This sequence is the same in the normal and AD brains. Dot-blot analysis of poly A+ RNAs from different human tissues indicates that relative to the coding sequence of ferritin H, expression of the 279 nt 3'UTR sequence varies among different tissues, is highest in the adult brain, and is very low in fetal brain. In normal adult hippocampus, ferritin H RNA with the novel 279 nt sequence localizes strongly to small non-neuronal cells, capillary endothelial cells, and to selected populations of neurons (granule cells of the dentate gyrus). Significant homology was observed between a region in the 279 nt 3'UTR segment of ferritin H RNA and the 3'UTR of cyclooxygenase-2 mRNA (an inducible iron-containing enzyme involved in prostaglandin synthesis). Possible functions for ferritin H protein derived from the novel message and for the elongated 3'UTR and 5'UTR are discussed.

Alzheimer's disease associated with mutations in presenilin 2 is rare and variably penetrant

Missense mutations in the presenilin 2 (PS-2) gene on chromosome 1 were sought by direct nucleotide sequence analysis of the open reading frame of 60 pedigrees with familial Alzheimer's disease (FAD). In the majority of these pedigrees, PS-1 and beta-amyloid precursor protein (beta APP) gene mutations had been excluded. While no additional PS-2 pathogenic mutations were detected, four silent nucleotide substitutions and alternative splicing of nucleotides 1338-1340 (Glu325) were observed. Analysis of additional members of a pedigree known to segregate a Met239Val mutation in PS-2 revealed that the age of onset of symptoms is highly variable (range 45-88 years). This variability is not attributable to differences in ApoE genotypes. These results suggest (i) that, in contrast to mutations in PS-1, mutations in PS-2 are a relatively rare cause of FAD; (ii) that other genetic or environmental factor modify the AD phenotype associated with PS-2 mutations; and (iii) that still other FAD susceptibility genes remain to be identified.

Accumulation of S100 beta mRNA and protein in cerebellum during infancy in Down syndrome and control subjects

S100 protein is a 20 kDA calcium-binding protein that accumulates during CNS maturation in mammals. The human gene coding for the beta subunit of S100 protein (S100 beta) is located on chromosome 21, in a subtelomeric position in 21q22.3. In order to investigate the effect of trisomy 21 on S100 beta gene expression, we performed Southern, Northern and Western blot analysis on DNA, RNA and protein, respectively, extracted from the cerebellum of control and Down syndrome (DS) subjects aged 1-18 months. Southern blot analysis revealed a novel EcoRI polymorphism in the S100 beta gene in two of 15 DNA samples examined, and a 1.5 gene dosage for S100 beta in DS. Northern and Western blot analysis showed an approximately 10-fold increase in S100 beta mRNA and protein levels between 1 and 18 months. No differences in the rates of accumulation of S100 beta mRNA and protein were observed between DS and normal subjects. These results demonstrate an increase in S100 beta mRNA and protein levels during infancy indicative of postnatal astrocytic maturation and show that there is no gross deregulation in the expression of the S100 beta gene in DS as a consequence of trisomy 21.

The transmission of phoneme-level information by multichannel tactile speech perception aids

Current research on the effectiveness of tactile aids for speech perception by hearing-impaired persons suggests that substantial training, lasting over months or years, is necessary for users to achieve maximal benefits from a tactile device. A number of studies have demonstrated the usefulness of training programs that include an analytic component, such as phoneme training, together with more synthetic tasks such as sentence identification and speech tracking. However, particularly in programs for children, it is desirable to structure training experiences so that easy distinctions are trained first, and more difficult distinctions are approached only later in training. In the present study, a systematic evaluation of phoneme-level information provided by the Tactaid VII, a multichannel tactile aid, was performed. Adult subjects were tested in minimal pairs and closed set phoneme discrimination and identification tasks under tactile aid alone, speechreading alone, and speechreading plus tactile aid conditions, to provide an inventory of stimulus identifiability and permit ranking of discriminations as easy or more difficult. Because these rankings might differ as a function of coarticulation effects, three different vowel contexts were tested for consonant stimuli. Results indicated that there were indeed considerable differences across vowel contexts, and that the /ae/ vowel context yielded the most identifiable stimuli. These data could be used by teachers and therapists to construct viable stimulus sets for training programs for tactile aid users.

Assessing preferences about the DNR order: does it depend on how you ask?

Despite increasing emphasis on advance directives, there has been little methodologic work to assess preferences about the "do not resuscitate" (DNR) order. This developmental work assessed, in a non-patient group, the performance of a probability-trade-off task designed to assess DNR attitudes, in terms of framing effects and stability of preferences. 105 female nursing students each completed one of two versions of the task. In version I (n = 58), the trade-off moved to increasingly negative descriptions of the outcomes of resuscitation (decreasing chance of survival and increasing risk of brain death), whereas in version II (n = 47), the trade-off moved to increasingly positive descriptions. One week later, repeat assessments were obtained for versions I (n = 35) and II (n = 28). The DNR preference scores were lower and more stable when the task moved to increasingly positive descriptions; perhaps this version of the task tends to weaken risk aversion. These results imply that care should be used in applying a probability trade-off task to the assessment of DNR preferences, since artefactual effects could be induced.

Localization of a new ferritin heavy chain sequence present in human brain mRNA to chromosome 11

Two types of ferritin heavy (H) chain clones have been isolated from cDNA libraries of human fetal and adult brain: one corresponds to the ferritin H chain mRNA that is abundant in liver and is called "liver-like" brain cDNA; the other contains an additional 279 nucleotide (nt) sequence in the 3' untranslated region and is called brain ferritin H chain cDNA. To map the 279-nt sequence, polymerase chain reaction (PCR) amplification was carried out using DNA from rodent x human hybrid cell lines containing single human chromosomes as templates, and oligomeric primers homologous to the 3' end of the 279-nt sequence (primer A) and to a coding sequence just 5' to the 279-nt sequence. Significant PCR product of the size expected from analysis of the brain ferritin H chain cDNA clones and a genomic ferritin H chain clone (487 bp) was generated only from hybrid-cell DNA containing human chromosome 11. This PCR product and the "liver-like" brain cDNA (lacking the 279-nt sequence) both hybridized to chromosome 11 fragments that are known to define the well-characterized functional liver ferritin H chain gene and a putative pseudogene. Preliminary data indicate that primer A (and thus the 279-nt sequence) maps to the functional ferritin H chain gene fragments, but binding to the pseudogene has not been ruled out.

Copper/zinc superoxide dismutase mRNA levels are increased in sporadic amyotrophic lateral sclerosis motorneurons

Mutations of the Cu/Zn superoxide dismutase (SOD-1) gene were recently implicated in the pathogenesis of familial amyotrophic lateral sclerosis (ALS). We measured SOD-1 mRNA levels in motorneurons of the more common sporadic form of the disease and found a 42% increase in ALS motorneurons (P = 0.058) as compared with controls. These results suggest that oxidative stress may also play a role in the pathogenesis of sporadic ALS.

Analysis of the functional effects of a mutation in SOD1 associated with familial amyotrophic lateral sclerosis

Mutations in the Cu, Zn superoxide dismutase (SOD1) gene have been reported in some pedigrees with Familial Amyotrophic Lateral Sclerosis (FALS). We have investigated the functional and structural effects of a Gly-->Ser mutation at codon 41 of SOD1 in a pedigree with FALS and the topography of SOD1 expression in the mammalian CNS. These analyses show that the 41Gly-->Ser mutation causes a 27% reduction in Cu, Zn SOD activity. SOD1 is transcribed at high levels in rat motoneurons and four other types of neurons homologous to upper motoneurons that degenerate in human ALS. However, SOD1 is transcribed at lower levels in other types of neurons, such as cerebellar Purkinje cells, which are not usually involved significantly in human ALS. On the other hand, immunocytochemical studies indicate that most types of rat neurons contain similar levels of Cu, Zn SOD immunoreactive protein. Nevertheless, these results suggest that the essential feature causing this subtype of ALS is either a reduction in Cu, Zn SOD activity in cell types that presumably critically require Cu, Zn SOD for protection against oxidative damage or the fact that the mutation in SOD1 associated with FALS results in a novel gain of function that is particularly deleterious to those cell types expressing SOD1 at high levels.

Neurofilament light and polyadenylated mRNA levels are decreased in amyotrophic lateral sclerosis motor neurons

The presence of large neurofilamentous accumulations in the perikaryon and proximal axon of motor neurons in amyotrophic lateral sclerosis (ALS) suggests that the expression of this abundant cytoskeletal protein may be altered. We performed quantitative in situ hybridization for the low molecular weight neurofilament subunit (NF-L) messenger RNA in six cases of sporadic ALS and six controls. We found a 41% decrease (p < 0.02) in the NF-L mRNA levels in anterior horn cells in ALS, with a 60% decrease (p < or = 0.01) in alpha motor neurons. This alteration may represent a non-specific response to axonal or neuronal injury or, alternatively, reflect the regenerative activity of residual normal motor neurons. NF-L mRNA levels were consistently low (in the third and fourth quartiles) in spheroid-bearing motor neurons, indicating that the neurofilamentous accumulations observed in ALS are not likely the result of overexpression of the NF-L gene. Total neuronal polyadenylated mRNA levels were also 50% lower (p = 0.02) in anterior horn cells and 48% lower (p < or = 0.05) in alpha motor neurons in ALS, possibly reflecting a decrease in selected mRNA species in diseased motor neurons.

Molecular genetic predictive testing for Alzheimer's disease: deliberations and preliminary recommendations

Forty-one participants representing diverse professional back-grounds attended a workshop on genetic predictive testing for familial Alzheimer's disease (FAD) on January 23, 1993 at Surrey Place Centre in Toronto, Canada. Rapidly emerging molecular genetic findings in AD indicate that predictive testing is now technologically feasible for selected individuals, although defining eligibility criteria remains problematic. Legal, ethical, biomedical, and psychosocial issues related to establishing predictive testing programs for AD were discussed at the workshop. This article reflects these discussions, provides the current biomedical background for them and examines the Huntington's disease (HD) predictive testing experience. Observations concerning molecular genetic predictive testing for AD in light of its genetic heterogeneity and clinical characteristics, such as usual later age of onset than HD, are presented. It is proposed that predictive testing for AD can now be cautiously offered in a research setting primarily according to the recommendations contained within the Ethical Issues Policy Statement on Huntington's Disease Molecular Genetics Predictive Test. However, in their application to AD, some points in the statement are considered to require emphasis, modification, or currently to be of uncertain applicability. This represents an initial step in an on-going process of debate concerning AD that will be required as new advances occur in genetic and clinical research and in bioethics.

Family with 22-derived marker chromosome and late-onset dementia of the Alzheimer type: II. Further cytogenetic analysis of the marker and characterization of the high-level repeat sequences using fluorescence in situ hybridization

We have further characterized an unusual 22p+ marker chromosome with a double nucleolus organizer region (dNOR) previously identified in a family with late-onset dementia of the Alzheimer type. G-banding and morphology of the marker's q arm were typically normal. However, the p+ arm had a terminal cytological satellite and a GT-positive region at the midpoint. Standard C-banding documented 2 C-positive regions: one was associated with the primary centromere; the other, which was at the midpoint of the p arm, was not associated with a constriction. With replication-banding, there was a darkly staining region in the middle of the p+ arm that resembled the pericentromeric region of a chromosome 21 or 22. Fluorescence in situ hybridization with pXlr 101, a probe recognizing the full repeating unit of rDNA, indicated that the marker had an unusually larger rDNA region; with pU 1.2, a probe recognizing the human rDNA promoter, the signal was a doublet. The marker had 2 signals with a beta-satellite probe, and a second signal in addition to that present at the primary centromere under low stringency with alpha-satellite probes and a classic satellite probe. Immunostaining of chromosome spreads after R-banding and ultraviolet (UV) denaturation showed that the major portion of the marker's p arm was highly methylated.

Immunoglobulin G subclasses in older persons with Down syndrome

IgG subclasses were measured in sera from 33 persons with Down syndrome (DS) (mean age 55 +/- 7 years) and 33 age- and sex-matched control individuals using a mouse monoclonal antibody based sandwich enzyme linked immunosorbent assay. Significantly higher levels of IgG1 and IgG3 and lower levels of IgG2 and IgG4 subclasses were found in the DS group compared to the control individuals. The higher levels of IgG1 and IgG3 subclasses found in DS persons were consistent with those seen in patients with autoimmune diseases and chronic viral infections; the lower levels of IgG2 and IgG4 subclasses were consistent with those seen in patients with recurrent infections. Our findings are similar to those reported in children with DS. We speculate that the subclass levels may have little or no relationship to the development of brain lesions typical of Alzheimer disease in older persons with DS. There were no significant differences between the levels of IgG subclasses of persons with DS showing signs of dementia of the Alzheimer type compared to those without such manifestations.

Age-associated chromosome 21 loss in Down syndrome: possible relevance to mosaicism and Alzheimer disease

We previously observed low level mosaicism (2-4% normal cells) in phytohemagglutinin-stimulated peripheral blood lymphocytes (PBL) in 29% of a small group of elderly persons with Down syndrome (DS). An analysis of cytogenetic data on 154 trisomy 21 cases (age 1 day to 68 years) showed that the proportion of diploid cells in such cultures significantly increased (P < 0.005) with advancing age. Thus, the "occult" mosaicism in PBL of the elderly persons with DS is likely due to the accumulation of cells that have lost a chromosome 21. A consequence of chromosome 21 loss could be uniparental disomy of the 2n cells, a factor that might have significant biological consequences if some chromosome 21 genes are imprinted. Loss of a chromosome 21 from trisomic cells might result in tissue-specific mosaicism and "classical" mosaicism in different age groups. Chromosome 21 loss might also be relevant to the development of Alzheimer-type dementia in DS and in the general population.

Methylation of the 5' flanking sequences of the ribosomal DNA in human cell lines and in a human-hamster hybrid cell line

In a human lymphoblastoid cell line (Z83) in which rDNA genes on chromosome 22 are amplified but transcribed at a low level, immunocytological studies with antibodies to 5 methylcytidine provided evidence for hypermethylation of the rDNA. The extent of methylation of the 5' flanking sequences of the ribosomal DNA was examined by comparing the size of restriction fragments obtained by digestion of genomic DNA with EcoRI and HpaII or EcoRI and MspI. Southern blots indicated hypermethylation of the 5' flanking sequences of many copies of rRNA genes in these cells, but not in a control lymphoblastoid cell line without rDNA amplification. Results obtained with a somatic hybrid human-hamster cell line, in which the rRNA genes on the single human chromosome 22 are inactive, showed that only a small fraction of the CCGG sites in the 5' flanking sequences of the transcriptionally silent rRNA genes in this hybrid were methylated. Since inactive rRNA genes can show such a minimal level of methylation, it is likely that the extreme hypermethylation of the amplified rRNA genes in Z83 occurred in association with their inactivation rather than following it.

Monozygotic twins concordant for late-onset probable Alzheimer disease with suspected Alzheimer disease in four sibs

Probable Alzheimer disease (AD) is described in 79-year-old male twins with monozygosity confirmed by DNA examination. The first twin to be affected began to show signs of intellectual deterioration at age 70. In the other, onset was at age 72. Four of their living sibs (current age range = 75-92) are also suspected to have AD. The possible roles of genetic and environmental factors in the development of AD in this sibship are discussed.

Molecular and prospective phenotypic characterization of a pedigree with familial Alzheimer's disease and a missense mutation in codon 717 of the beta-amyloid precursor protein gene

We present prospective clinical and neuropathologic details of a pedigree segregating familial Alzheimer's disease (FAD) associated with a mutation (G----A substitution) at nucleotide 2149 in exon 17 of the amyloid precursor protein (APP) gene. This mutation, which is predicted to cause the missense substitution of isoleucine for valine at codon 717 of APP, cosegregated perfectly with the FAD trait (lod score = 3.49 at theta = 0.00). The earliest clinical manifestations of the disease relate to deficits in memory function, cognitive processing speed, and attention to complex cognitive sets. These changes occurred in the absence of changes in nonmemory language and visuospatial functions. The neuropathologic features of FAD associated with the APP717 mutation in this family include severe neuronal loss, abundant neurofibrillary tangles, amyloid plaques, and amyloid angiopathy. These results provide independent confirmation that mutations in the APP gene are linked to the FAD trait in some families.

A family with multiple instances of definite, probable and possible early-onset Alzheimer's disease

A family with a multigenerational history of proven or suspected early-onset Alzheimer's disease (AD) consistent with autosomal-dominant inheritance is described. To date, the pedigree comprises five generations in which there are 13 known affected individuals. The mean age of onset of cognitive deficits in those for whom data are available (n = 11) is 47.6 (s.d. 3.0) years and the mean age of death (n = 10) is 58.8 (s.d. 4.0) years. The variability in the extent and quality of available data illustrates the diagnostic difficulties encountered in ascertaining such an extended pedigree, and the need for caution in interpreting the evidence.

Anomalous gene expression in Alzheimer disease: cause or effect

Altered chromatin conformation and increased amounts of aluminum have been observed in the brains of patients with Alzheimer disease. These factors have been shown to affect gene regulation. In this report, we describe how these changes may selectively alter the pool size of the human light chain neurofilament gene and play a fundamental role in the expression of this disease.

Family with 22-derived marker chromosome and late-onset dementia of the Alzheimer type: I. Application of a new model for estimation of the risk of disease associated with the marker

We have identified 2 sisters with probable dementia of the Alzheimer type who have an unusual 22-derived marker chromosome with a greatly elongated short arm containing 2 well-separated nucleolus organizer regions. A marker chromosome similar in appearance is uncommon in the general population. Eleven of 24 of their biological relatives were also found to have the marker. The known pedigree of this family encompasses 6 generations in 2 of which there is evidence of 10 cases of dementia of the Alzheimer type. The average age-at-onset of dementia is 65.8 +/- 5.5 years; the average age-at-death among those apparently affected is 74.9 +/- 8.3 years. A new model for the estimation of risk was applied to the family data. Persons in this family with the marker were found to be 4 times more likely to develop dementia than those without the marker, the 95% confidence interval for this risk being 1-50. The probability that the association of dementia and the marker is due to chance alone is .05 (1 in 20).

Localization and quantitation of 68 kDa neurofilament and superoxide dismutase-1 mRNA in Alzheimer brains

The technique of in situ hybridization with tritiated RNA probes was used to study the expression of the 68 kDa neurofilament (NF68) gene and the superoxide dismutase-1 (SOD-1) gene in the brains of Alzheimer's disease (AD) patients. Messenger RNA (mRNA) for these proteins was localized and quantified in single cells of formalin-fixed, paraffin-embedded sections of 4 pairs of AD and Huntington's disease (HD) brains from patients matched for age at death and autopsy interval. The cerebellar cortex and hippocampal CA1 and CA2 regions were compared in these two groups of subjects, since in AD the CA2 region of the hippocampus and the cerebellum have been found to be relatively unaffected by the Alzheimer process in comparison to the hippocampal CA1 region. The amount of NF68 mRNA was reduced by approximately 50% in pyramidal cells of both the CA1 and CA2 of AD hippocampus (P less than 0.001), and by 15% in the Purkinje cells of AD cerebellum (P less than 0.05) relative to that of the HD individuals. SOD-1 mRNA was reduced by about 22% in the CA1 of AD brains (P less than 0.001) with no corresponding reduction in the CA2, and by only 5% in the AD cerebellum (P greater than 0.5). The paired design of the study suggests that these results are not simply attributable to the effects of autopsy interval or the agonal process in each patient's death.

Autoimmune thyroiditis associated with mild "subclinical" hypothyroidism in adults with Down syndrome: a comparison of patients with and without manifestations of Alzheimer disease

Serum tests of thyroid function were compared in Down syndrome (DS) patients with and without manifestations of Alzheimer disease (AD). Relative to control individuals, DS patients had, overall, lower mean total T4 (P = 0.070) and T3f (P = 0.015), higher T3U (P = 0.013) and TSH (P = 0.020), no difference in free T4, and higher thyroid antithyroglobulin (ATA) (P = 0.033) and antimicrosomal autoantibody (AMA) titres (P = 0.0097). Similar trends were apparent in DS males and females, and in DS patients off all drugs. In an analysis of case/control pairs with corrections for age and sex, DS patients with AD manifestations (n = 9) had significantly lower T3 (P = 0.029) and higher AMA (P = 0.043) than paired control individuals, whereas DS patients without AD manifestations (n = 20) had significantly lower T3 (P = 0.013) but higher ATA (P = 0.0065). T3 was significantly lower in the DS patients with AD manifestations than in the unaffected (P = 0.0013). These data suggest that autoimmune thyroiditis associated with a mild "subclinical" form of hypothyroidism is common in adult DS patients and more pronounced in patients with AD manifestations than in those without. This "subclinical" hypothyroidism may contribute to cognitive deficits in ageing DS patients.

Red cell superoxide dismutase, glutathione peroxidase and catalase in Down syndrome patients with and without manifestations of Alzheimer disease

The activities of red blood cell enzymes that scavenge the superoxide radical and hydrogen peroxide were measured in severely to profoundly retarded adult Down syndrome (DS) patients with and without manifestations of Alzheimer disease (AD), and control individuals matched for sex, age, and time of blood sampling. Cu,Zn superoxide dismutase (SOD-1) and glutathione peroxidase (GSHPx) activities were significantly elevated (1.39-fold and 1.24-fold, respectively) in DS individuals without AD. When an adjustment was made for the SOD gene dosage effect, DS patients with AD manifestations had significantly lower SOD levels than the matched control individuals. In contrast, DS patients with and without AD had a similar elevation in GSHPx (an adaptive phenomenon). The mean catalase (CAT) activity was no different in DS and control individuals; however, in a paired regression analysis, DS patients without AD had marginally lower CAT activity than control individuals, whereas DS patients with AD had slightly but not significantly higher CAT activity. Thus, AD manifestations in this DS population are associated with changes in the red cell oxygen scavenging processes.

Human papillomavirus infection of morphologically normal cervical epithelium adjacent to squamous dysplasia and invasive carcinoma

We have begun a systematic study of human papillomavirus (HPV) infection in colposcopically and/or morphologically normal epithelium of the uterine cervix. Paired biopsies were taken from the lesions (cervical intraepithelial neoplasia [CIN], condyloma, invasive carcinoma) and from the normal-appearing adjacent epithelium 3 to 5 mm from the edge of the lesion. Myometrium or ectocervical epithelium from patients who had undergone hysterectomy for reasons other than genital dysplasia or malignancy served as controls. One biopsy was examined histologically. DNA from the second biopsy was digested with Pst I, and the presence or absence of HPV was determined by Southern blotting using HPV-16 DNA as a probe. HPV was not detected in any of the 12 control samples. Of 30 patients with CIN and/or condyloma, five of 18 who were HPV-positive had either HPV-16 (three cases) or virus resembling HPV-31 (two cases) in the lesion and adjacent epithelium. Of seven patients with invasive carcinoma, four had HPV in the lesion and adjacent epithelium; two of these four patients had typical HPV-16. Such infection of apparently normal epithelium has major implications for our understanding of the pathogenesis, treatment, and follow-up of patients with cervical neoplasia.

Carrier detection in hemophilia A: ABO blood group, multiple measurements, and application of logistic discrimination

In healthy 20- to 50-year-old women, the ABO blood group has a significant effect on levels of von Willebrand factor (VWF:Ag, formerly VIIIR:Ag) and on factor VIII activity (F.VIII:C). However, there is no significant effect of ABO group or subject age on the ratio log e(F.VIII:C/VWF:Ag). Multiple measurements of the "ratio" on possible carriers of hemophilia A may be combined with pedigree information using logistic discrimination to yield final risk assessment. To reduce misclassification of carriers as normal women, a lower limit, specified by the logistic model, is set on the logistic carrier probabilities. In this study, the proportion of blood group A for a population of obligate carriers was significantly higher than that expected for the general population (60% vs. 42%); for a population of control women it was lower than expected (22.5 vs. 42%). The effect for the carriers came primarily from daughters of affected fathers, as 81.3% were of blood group A. These observations indicate that a "universal" discriminant should be applied with caution.

Localization of the 68,000-Da human neurofilament gene (NF68) using a murine cDNA probe

A recent investigation, using a human genomic probe, has indicated that the 68,000 dalton neurofilament gene (NF68) is on the short arm of chromosome 8. We have used a murine cDNA probe on 65 metaphase spreads in situ to localize the human NF68 gene to 8p21 (20/370 grains; p less than 0.0001). In addition, we have found secondary hybridization sites at the centromeric region of chromosome 2 and the long arm of chromosome 7, which are putative loci for other intermediate filaments.

Making the most of multiple measurements in estimating carrier probability in Duchenne muscular dystrophy: the Bayesian incorporation of repeated measurements using logistic discrimination

In carrier detection studies, females-at-risk are usually tested several times if the results are ambiguous, whereas subjects in the control and obligate carrier reference groups may not be tested as often. The question is how to incorporate the multiple measurements most effectively with information in the family pedigree into combined carrier risks. Sets of measurements on individuals are not independent, but are related with the correlation coefficient 0 less than rho less than 1. We have developed a procedure for incorporating repeated measurements on individuals and their a priori chance of having the disease into logistic models. This procedure utilizes the set of measurements and an estimate of rho. We describe application of this procedure to carrier detection in Duchenne muscular dystrophy (DMD) using serum creatine kinase (CK) measurements as the biochemical indicator of carrier status. Estimates of rho for controls and obligate DMD carriers did not differ significantly from 0.5. Repeated testing with use of rho = 0.5 significantly decreased the median logistic carrier probability for controls and increased it for carriers. In some cases four to six rather than the three CK tests conventionally used in genetic counseling were necessary to obtain a stable logistic carrier probability for a subject.

DUCHEN: an interactive computer program for calculating heterozygosity (carrier) risks in X-linked recessive lethal diseases, and its application in Duchenne muscular dystrophy

The program DUCHEN calculates the probability that a woman is a carrier of an X-linked, lethal recessive disease on the basis of information in the woman's family and any available biochemical data. It is easily used by persons without computer knowledge or experience. The present version can accommodate families consisting of up to 100 people in seven generations. Risks may be estimated on the basis of pedigree information only, or with the inclusion of one or more types of biochemical test results. Biochemical data are incorporated with pedigree information into final risks using the powerful statistical technique of logistic discrimination, a procedure particularly suited for the separation of non-normal populations on the basis of overlapping quantitative characteristics. Mutation rates are specified separately for males and females. DUCHEN is available in FORTRAN 77, IBM BASIC, and Applesoft BASIC, and may be used on a variety of mainframe or microcomputers. The model was used to calculate risks for 375 girls and women in 46 families with Duchenne muscular dystrophy (DMD); serum creatine kinase tests had been carried out on 167 of these subjects who were of reproductive age. Carrier probabilities equal to or lower than the population risk (0.0004) were obtained for 21% of the aunts and 43% of the cousins of affected boys from families with an isolated case of DMD and for 14% of the cousins of affected boys from families with a known DMD history. DUCHEN should assist counsellors in determining which members of large families should be further examined using either standard biochemical carrier detection methods or DNA marker studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Catalase: an old enzyme with a new role?

Although animal catalase has been studied for decades, its physiological role has remained perplexing. It has two enzymatic functions, not only catalyzing the breakdown of H2O2 into O2 and H2O, but also in the presence of low concentrations of H2O2 catalyzing the oxidation of electron donors such as ethanol or phenols. In this article, I have summarized some well-known properties of the enzyme and have also described several recently discovered features. Of particular interest is the finding that, although catalase has been regarded as an intracellular enzyme, there is published evidence for its association with the plasma membrane of the erythrocyte. Moreover, recent work from my laboratory indicates that in vitro at alkaline pH in the presence of Mg2+, the biologically active diphenols (beta-3,4-dihydroxyphenylalanine and the beta-adrenergic agonists isoproterenol, norepinephrine, and epinephrine) appear to function as electron donor substrates for human erythrocyte catalase and inhibit the production of O2 from H2O2 at micromolar concentrations. The beta-adrenergic antagonist propranolol inhibits O2 production much less effectively and appears to competitively inhibit the reaction of catalase with epinephrine. These observations suggest an analogy between catalase and the beta-adrenergic hormone receptor and raise many questions of interest to basic science, health, and disease.

Serum myoglobin in Duchenne muscular dystrophy carrier detection: a comparison with creatine kinase and hemopexin using logistic discrimination

Logistic discrimination was used to assess the effectiveness of serum myoglobin (Mb), creatine kinase (CK), and hemopexin (H) measurements in identifying Duchenne muscular dystrophy (DMD) carriers. Subjects included 36 obligate carriers, 46 age-matched control women, 30 mothers of isolated cases, and 14 DMD patients. The percentages of obligate carriers with logistic carrier probabilities exceeding the upper normal 95th centile (or 97.5th centile) were: CK alone, 63% (50%); Mb alone, 65% (62%); CK and Mb, 66% (62%); CK and H, 78% (65%); CK H and Mb, 72% (65%). In this study, Mb identified more carriers than CK at the 97.5% level, but there was no advantage in using Mb measurements with CK. CK provided slightly better overall separation of the control and carrier groups than Mb. CK, Mb, and H in combination provided significantly better separation than CK and H, or CK alone.

Duchenne muscular dystrophy carrier detection using logistic discrimination: serum creatine kinase, hemopexin, pyruvate kinase, and lactate dehydrogenase in combination

In the absence of an unambiguous test for identifying Duchenne muscular dystrophy (DMD) heterozygotes, methods are needed for combination of the results of individually equivocal tests as effectively and rationally as possible. Tw used logistic discrimination to assess the effectiveness of measurements of serum creatine kinase, hemopexin, pyruvate kinase, and lactate dehydrogenase alone and in various combinations in identifying DMD carriers. We analyzed 127 serum samples from 63 normal female controls (20-40 years old) and 67 from 38 obligate DMD carriers. The best two tests to use in combination were creatine kinase and hemopexin, and these two, with lactate dehydrogenase, were the best three. t the 95% level (with 5% of controls misclassified), 54% of the carriers were identified by CK alone, whereas 88% were identified by means of the four tests. Although a small proportion of known carriers still cannot be identified, application of the four tests to a group of 45 possible carrier mothers of isolated cases of DMD resolves the population into fairly discrete "normal" and "abnormal" subgroups. Thus, if bias of selection can be eliminated, application of logistic discrimination may permit a direct estimate of the proportion of mothers of affected boys who are homozygous normal.

Serum creatine kinase in the detection of Duchenne muscular dystrophy carriers: effects of season and multiple testing

The usefulness of serum creatine kinase (CK) activity in the detection of Duchenne muscular dystrophy (DMD) carriers is dependent upon a reliable control distribution. In controls there is a small but reproducible seasonal variation in CK activity, with a statistically significant variation in the upper 95th percentile (78 IU/liter in May, 53 IU/liter in November, as compared with 67 IU/liter for the whole calendar year). Because CK values in DMD heterozygotes are higher in November than in May, the carrier detection rate may be highest in November. Failure to consider this seasonal variation in controls may cause misclassification of too many normal subjects. If tests are conducted throughout the year, however, the seasonal influence can be reduced by serial testing at intervals of several months. In this case, use of the highest of the results obtained in 3 tests compared with the normal range of single measurements misclassifies too many normal subjects. Use of the mean of 3 determinations provides more accurate classification.

Creatine kinase isozyme transition in chicks with hereditary muscular dystrophy

In both normal chicks and chicks with hereditary muscular dystrophy the BB (brain) and MB (hybrid) isozymes were the predominant forms of creatine kinase (CK) activity in embryonic skeletal muscle. As myogenesis progressed, activity due to the MM (muscle) isozyme progressively increased, and by 1 week ex ovo, the MM isozyme accounted for approximately 97% of total muscle activity in both genotypes. During this time, the proportion of the MM isozyme was slightly but significantly lower in dystrophic muscles. After hatching the proportion of the MB isozyme and its total activity decreased in normal muscle, but increased in dystrophic pectoral muscle, and by 5 months ex ovo, the MB isozyme accounted for 10% of total CK activity. Prior to hatching there was no consistent difference in total CK activity between normal and dystrophic tissues, but by 1 week after hatching and thereafter, total CK activity was significantly lower in dystrophic pectoral muscle.

Duchenne muscular dystrophy carrier detection using logistic discrimination: serum creatine kinase and hemopexin in combination

Creatine kinase (CK) activity and hemopexin concentration were measured in 208 serum samples from 104 normal females and 22 obligate carriers of Duchenne muscular dystrophy (DMD) 20-40 years old. Logistic discrimination was used to assess the effectiveness of the parameters alone or in combination in identifying DMD carriers. In this approach, a serum sample with particular CK, hemopexin, or a combination of CK and hemopexin values is given a probability that if drawn at random from a defined mixture of controls and carriers, it comes from a carrier. The carrier probability based on the biochemical tests can be directly combined with the carrier probability determined from a woman's pedigree to yield a final posterior probability that she is a carrier. When CK and hemopexin were considered individually, 65 and 27% of the carriers, respectively, could be distinguished from 95% of the controls. When the two tests were used in combination, 82% of the carriers could be distinguished from 95% of the controls. When the two-test method was applied to 93 possible carriers, 35 women were classified as carriers, whereas only 29 were identified using CK alone. This method can be extended to include other variables in order to further improve the identification of DMD carriers. It can also be applied to carrier detection in other genetic disorders.

Serum creatine kinase and pyruvate kinase in Duchenne muscular dystrophy carrier detection

The incidence of elevated serum creatine kinase (CK) and pyruvate kinase (PK) activities was compared in 20 definite carriers of Duchenne muscular dystrophy (DMD), 47 possible carriers, and 42 female controls. When adult age was not regarded as a variable, 70% of the definite carriers had elevated PK, 55% had elevated CK, and 75% had elevated PK or elevated CK or both, 38% of the possible carriers had elevated PK, 19% had elevated CK, and 40% had elevated PK or elevated CK or both. The detection efficiency of the CK test was influenced by the age of the subjects: the upper normal limit of serum CK in the adult controls was at the minimum between 21 and 35 years of age, and CK activity in some carriers declined from elevated to normal levels with increasing age. With these considerations, 70% of definite carriers had elevated CK and 80% had elevated PK and/or CK; 34% of the possible carriers had elevated CK and 43% had elevated PK and/or CK. On the basis of the PK and CK measurements, only 16 of 24 possible carrier mothers were likely to be DMD carriers, implying that the other 8 were non-carrier mothers of new mutant sons.

The kinetics of in vitro reoxidation and reduction of the inter heavy--light chain disulfide bond in an unusual murine immunoglobulin G myeloma protein lacking inter-heavy chain disulfide bonds

After 5 years of subcutaneous transfer in Balb/C mice, our MOPC 173 myeloma tumour line (originally an IgG2a,κ H2L2-producer) exclusively synthesized an unusual IgG2b,κ protein lacking inter-heavy (H) chain disulfide bonds. This protein was designated MOPC 173B. On sodium dodecyl sulfate – polyacrylamide gel electrophoresis, it migrated with an apparent molecular weight of 77 000; following complete reduction and alkylation, the mobilities of its constituent H and light (L) chains were found to differ slightly from those of MOPC 173 H2L2. MOPC 173B was serologically identical to another typical IgG2b,κ myeloma protein, MOPC 195, and peptide mapping studies showed that it possessed only the inter H–L disulfide bond characteristic of typical IgG2b,κ proteins. In a nondissociating solvent, the sedimentation coefficient of the protein was 6.3S even at concentrations as low as 0.2 mg/ml, indicating that noncovalent interactions existed between two half-molecule subunits. Since this unusual IgG myeloma protein contained only a single category of interchain disulfide bridge, the inter H–L bond, it was an ideal model system for characterization of the kinetics of formation and reduction of interchain disulfide bonds. The kinetics of the glutathione-catalyzed reoxidation of the inter H–L disulfide bridge in MOPC 173B followed an apparent second-order rate equation. In contrast, reduction of its inter H–L bridge under anaerobic conditions with dithioerythritol in excess, was strictly a first-order process and not a simple reversal of the reoxidation. These studies provide the basis for the more complex mathematical models that describe the reoxidation and reduction of typical immunoglobulin molecules.

The covalent assembly of MOPC 104 E immunoglobulin M. Identification of a heavy chain dimer, a complex of two heavy chains and one light chain, and a distinctive form of monomer as intracellular intermediates

The covalent assembly of MOPC 104E immunoglobulin M (IgM) was studied in mouse myeloma tumour cells producing a twofold molar excess of light chains (L's), using pulse-chase and continuous-label experiments with radioactive amino acids. In previous experiments with myeloma tumour cells which produced a large excess of L's, the half molecule (HL) was the only intermediate identified as a precursor of the intracellular monomer (LHHL). In the current experiments, heavy chain dimer (HH) and a disulfide-bonded intermediary containing two H chains and one L chain (HHL) also functioned as precursors of the monomeric subunit. These experiments indicate that the degree of excess L production by the tumour cells appears to influence the amounts of intracellular intermediates, and that MOPC 104E IgM assembles via the same pathways which are utilized in the assembly of mouse immunoglobulin G (IgG). On sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS–PAGE), the radiolabelled intracellular monomer which was synthesized by the mouse myeloma tumour cells in culture migrated slightly more slowly than the monomeric subunit liberated from MOPC 104E IgM by reduction with low concentrations of dithiothreitol. The distinctive mobility of the intracellular monomer did not result from the presence of radiolabelled, disulfide-bonded joining (J) chain. In addition, the apparent molecular weights of the constituent heavy IgM chain (μ) and L's of the intracellular monomer, as judged by SDS–PAGE, were not significantly different from those of secreted μ and L.

Human thymus-leukemia-associated antigen: isolation and partial characterization

Human thymus-leukemia-associated antigen (HThy-L), a saline-soluble antigen, was previously detected by immunodiffusion (but not on the cell surface) in significant quantity in extracts of normal thymocytes, cells from cultured T-cell lines, and erythrocyte-rosette-positive leukemia blasts. Two species of HThy-L were identified and isolated from normal human thymus tissue after extraction in tris buffer, ammonium sulfate fractionation, acid precipitation of inactive fractions, DEAE-cellulose (DE-52) chromatography, Sephadex G-100 gel filtration, and carboxymethyl-cellulose (CM-52) chromatography; On Sephadex G-100, both HThy-L species had a similar molecular weight (40,000--50,000), but they eluted in different positions on DE-52 and CM-52. Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that each of the 2 HThy-L species contained 2 components with molecular weights of approximately 43,000 and 23,000. Further purification of HThy-L on Sephadex G-50 showed that the 43,000-dalton component possessed HThy-L activity.

Functional differentiation of B lymphocytes in congenital agammaglobulinemia. I. Generation of hemolytic plaque-forming cells

Despite the absence of B lymphocytes, peripheral blood lymphocytes (PBL) from four of five patients with congenital agammaglobulinemia (cAgamma) generated a specific hemolytic plaque-forming cell (HcPFC) response in vitro to sheep red blood cells and ovalbumin. The kinetics, antigenic, and cellular requirements were similar to normals, but significantly less HcPFC were found in patient cultures. Normal but not patient HcPFC-precursor cells were inactivated by treatment with anti-mu antisera whereas generated HcPFC in both controls and patients were sensitive to treatment with anti-mu. Pokeweed mitogen (PWM) and dextran sulfate (DXS) enhanced the HcPFC-response of normal PBL; cAgamma-cells were unresponsive to DxS and, in the presence of PWM, the development of HcPFC was inhibited. These findings indicate the presence of B lymphocyte precursors in the majority of patients with cAgamma investigated.

Functional differentiation of B lymphocytes in congenital agammaglobulinemia. II. Immunochemical analysis of the in vitro primary immune response

Cultures of peripheral blood lymphocytes (PBL) in which specific hemolytic plaque-forming cells (HcPFC) had been induced were labeled with 14C-amino acids. Antigen-specific products in the culture supernatants were characterized by using indirect immune precipitation in conjunction with specific immunoabsorbents and/or gel filtration followed by SDS-polyacrylamide gel electrophoresis. After 5 days of culture with antigen (sheep red blood cells or ovalbumin) newly synthesized IgM and specific IgM antibody were demonstrated in culture supernatants from normal donors and from four out of five patients with congenital agammaglobulinemia (cAgamma). Secreted products bound specifically to antigen and pretreatment of labeled supernatants with anti-mu and anti-L chain antisera, but not with anti-gamma antiserum, prevented binding. Typical mu- and L chains constituted only a proportion of the anigen-binding peptides recognized by the anti-mu reagents. Induction of IgM antibody synthesis was dependent on the presence of antigen and was correlated with the generation of HcPFC. No major differences between the antigen-induced products of cAgamma and normal PBL were observed. These findings suggest that in the absence of terminal B cell differentiation in vivo, certain patients with cAgamma possess precursor cells that can respond to antigen in vitro with the synthesis of specific humoral products, including IgM antibody.