APOE 4 and hip fracture risk in a community-based study of older adults

OBJECTIVES

To investigate whether the APOE 4 allele was associated with increased risk of hip fracture in an older community-based sample and whether such an increased risk was independent of dementia and history of falling.

DESIGN

Case-control study nested within a prospective community study.

SETTING

The Monongahela Valley Independent Elders Survey (MoVIES), an ongoing prospective community study of older adults in southwestern Pennsylvania.

PARTICIPANTS

A total of 899 MoVIES participants (63.9% women; mean age, 76.2 years, SD = 4.9 years), who provided both information on hip fractures and blood samples for genotyping.

MEASUREMENTS

Interview questions regarding hip fractures and falls, polymerase chain reaction to determine APOE genotype, and clinical assessment using a standardized protocol to determine the presence or absence of dementia.

RESULTS

Twenty-five subjects reported having hip fractures in the year preceding screening interviews. Subjects with one or two APOE 4 alleles were twice as likely as subjects without an APOE 4 allele to report hip fractures (age-adjusted OR = 2.1, 95% CI: 0.9-4.7). Based on multivariate analysis, subjects with a history of falling were more likely to report hip fractures (OR = 4.7, 95% CI: 2.1-10.8). After adjusting for history of falls and diagnosis of dementia, subjects with an APOE 4 allele were still twice as likely to report hip fractures (adjusted OR = 2.1, 95% CI: 0.9 - 4.7).

CONCLUSIONS

The APOE 4 allele appears to be a risk factor for hip fracture, independent of the effect of dementia and falling. Theoretically, this may be mediated by alterations in vitamin K metabolism. Caution should be used in interpreting these results, because the 95% confidence intervals for the odds ratios include 1.

Inhibitory effect of interleukin-8 on the secretion of platelet-activating factor acetylhydrolase by human decidual macrophages

OBJECTIVE

To determine whether interleukin-8 (IL-8) regulates platelet-activating factor acetylhydrolase (PAF-AH) secretion by decidual cells in vitro.

METHODS

Decidual macrophages were obtained from human term decidual tissue by enzymic digestion and Ficoll-Paque centrifugation. The effect of IL-8 and phorbol esters on the secretion of PAF-acetylhydrolase by these cells was examined.

RESULTS

IL-8 inhibited PAF-AH secretion by decidual macrophages in a dose-dependent manner. The inhibition was reversed partially by antibodies against tumor necrosis factor-alpha and IL-1 beta. IL-8-induced inhibition was blocked partially by the protein kinase C (PKC) inhibitors, sphingosine, and H-7 1-(5-isoquinoline sulfonyl)-2-methylpiperazine. A PKC activator, 12-O-tetradecanoyl phorbol 13-acetate, decreased PAF-AH secretion.

CONCLUSION

IL-8 may increase the PAF concentration in the decidua via its inhibitory effect on PAF-AH secretion by decidual macrophages. IL-8-induced inhibition of enzyme secretion may have been mediated in part by PKC-dependent signal transduction.

Depressive symptoms, cognitive impairment and functional impairment in a rural elderly population in India: a Hindi version of the geriatric depression scale (GDS-H)

OBJECTIVE

To measure depressive symptomatology in a largely illiterate elderly population in India, using a new Hindi version of the Geriatric Depression Scale (GDS-H), and to examine its distribution and associations with age, gender, literacy, cognitive impairment and functional impairment.

DESIGN

A Hindi version of the Geriatric Depression Scale was developed and administered to participants along with measures of demographic characteristics, cognitive functioning and functional ability.

SETTING

The rural community of Ballabgarh in northern India.

PARTICIPANTS

A community sample of 1554 mostly illiterate Hindi-speaking residents of Ballabgarh aged 55+.

MEASURES

The Hindi version of the Geriatric Depression Scale (GDS-H); the Hindi Mental State Exam (HMSE); the Everyday Abilities Scale for India (EASI); age, gender and literacy.

RESULTS

The GDS-H had high internal consistency and a factor structure comparable to the original English language version. The overall distribution of scores was higher than reported from other populations. Greater numbers of depressive symptoms, as measured by higher scores on the GDS-H, were associated with older age and illiteracy. Among the illiterate, there was no gender difference while among the literate, higher GDS-H scores were found among women. Cognitive impairment and functional disability were independently associated with higher scores on the GDS-H after adjustment for age, gender and literacy.

CONCLUSION

A reliable and valid Hindi version of the GDS has been developed. Depressive symptoms as measured by the GDS-H were prominent in this elderly illiterate northern Indian population and strongly associated with both cognitive and functional impairment.

Small head size is related to low Mini-Mental State Examination scores in a community sample of nondemented older adults

The objective of this analysis was to determine the relationship, if any, of head size to performance on a cognitive screening test among elderly nondemented adults participating in a community-based survey. The study sample included 825 subjects (533 women, 292 men), age 70 to 95 years. Multivariate analyses, with adjustment for age and education, revealed that smaller head size was associated with low Mini-Mental State Examination (MMSE) scores (i.e., below the 10th percentile) in both men and women. For every 1-centimeter increment in head size, there was a corresponding reduction of approximately 20% in the probability of a low MMSE score.

Plasma platelet-activating factor acetylhydrolase activity is not associated with premature coronary atherosclerosis

Platelet-activating factor acetylhydrolase activity in plasma was compared between 72 subjects with angiographically normal coronary arteries and matched controls with clinically significant obstruction. No difference was seen, and we conclude that variation in plasma platelet-activating factor acetylhydrolase activity is not a risk factor for coronary artery disease.

An immortalized, type-1 astrocyte of mesencephalic origin source of a dopaminergic neurotrophic factor

Rat embryonic d 14 (E14) mesencephalic cells, 2.5% of which are glioblasts, were incubated in medium containing 10% of fetal bovine serum for 12 h and subsequently expanded in a serum-free medium using basic fibroblast growth factor (bFGF) as the mitogen. On a single occasion, after more than 15 d in culture, several islets of proliferating, glial-like cells were observed in one dish. The cells, when isolated and passaged, proliferated rapidly in either a serum-free or serum-containing growth medium. Subsequent immunocytochemical analysis showed that they stained positive for GFAP and vimentin, and negative for A2B5, O4, GalC, and MAP2. Serum-free conditioned medium (CM) prepared from these cells caused a fivefold increase in survival and promoted neuritic expansion of E14 mesencephalic dopaminergic neurons in culture. These actions are similar to those exerted by CM derived from primary, mesencephalic type-1 astrocytes. The pattern of expression of the region-selective genes; wnt-1, en-1, sis showed that 70% of the cells were heteroploid, and of these, 50% were tetraploid. No apparent decline in proliferative capacity has been observed after 25 passages. The properties of this cell line, named ventral mesencephalic cell line one (VMCL1), are consistent with those of an immortalized, type-1 astrocyte. The mesencephalic origin of the cell line, and the pattern and potency of the neurotrophic activity exerted by the CM, strongly suggest that the neurotrophic factor(s) identified are novel, and will likely be strong candidates with clinical utility for the treatment of Parkinson's disease.

Increased survival of dopaminergic neurons by rasagiline, a monoamine oxidase B inhibitor

Both deprenyl and rasagiline (R(+)-N-propargyl-1-aminoindane mesylate), at a concentration of 1-10 microM, increased survival in vitro of rat E14 mesencephalic dopaminergic neurons that had been primed with 10% serum for 12 h (p < 0.05). Rasagiline, but not deprenyl, also increased total neuronal (MAP2-positive) survival (p < 0.05) Under serum-free conditions, rasagiline, but not deprenyl, retained its neuroprotective action on dopaminergic neurones. GABAergic neurons were not affected by either deprenyl or rasagiline. Clorgyline, an MAO-A inhibitor, did not exert any of these effects. The protective action of rasagiline on dopaminergic neurons, even under stringent serum-free conditions, is striking, and warrants further investigation for a role in the treatment of Parkinson's disease.

Determinants of plasma platelet-activating factor acetylhydrolase: heritability and relationship to plasma lipoproteins

Plasma platelet-activating factor acetylhydrolase (PAF-AH) is the enzyme that inactivates PAF (1-alkyl-2-acetyl-sn-glycero-3-phosphocholine). We determined the relative contributions of genetic and environmental factors to variation in plasma PAF-AH activity in 240 individuals from 60 nuclear families. Regression of mean-offspring PAF-AH activity on the mid-parent value indicated that 62% of the variation in plasma PAF-AH activity was heritable. Spousal values were weakly negatively correlated, indicating that familial aggregation of PAF-AH activity is due to genetic rather than to environmental factors. Among normolipidemic individuals, plasma PAF-AH activity was strongly correlated with the plasma concentration of low density lipoprotein cholesterol (LDL-C), and treatment with lovastatin resulted in proportional decreases in plasma PAF-AH activity and LDL-C concentrations. To further elucidate the relationship between PAF-AH and plasma concentrations of LDL, plasma PAF-AH activity was measured in families with well-defined, monogenic disorders of LDL metabolism. Plasma PAF-AH activity cosegregated with plasma LDL-C concentrations in familial hypercholesterolemia, but not in familial hypobetalipoproteinemia. We speculate that the rate of removal of LDL from the circulation may determine the clearance rate of PAF-AH, thereby modulating the activity of PAF-AH in blood.

The central role of PAF in necrotizing enterocolitis development

We have addressed two critical questions concerning NEC development. 1) Why is the neonatal intestine particularly susceptible to necrosis? and 2) Does PAF play a critical role in NEC development? We have found that intestinal tissue of the newborn has the highest specific activity for the acetyltransferase of the de novo pathway. It is suggested that the high capacity of this tissue to synthesize PAF may contribute to the fact that the necrosis of the newborn is more prevalent in this tissue. We have previously reported that dexamethasone lowers the activity of acetyl-CoA:lyso-PAF acetyltransferase in liver and spleen. This hormone also cause an increase in plasma PAF-acetylhydrolase activity and an increased secretion of PAF-acetylhydrolase by various macrophages. It would, therefore, appear that the beneficial effects of glucocorticoids on the prevention of NEC may be due to both increased inactivation of PAF as caused by the increase in PAF-acetylhydrolase as well as a decrease in PAF synthesis. We are presently investigating the effect of glucocorticoids on acetyl-CoA: alkyl-lyso-sn-glycero-3-phosphate acetyltransferase. The reported studies in which NEC was prevented by intravenous infusion of recombinant PAF-acetylhydrolase provides further documentation as to the importance of PAF in the development of NEC. The specific activity of PAF-acetylhydrolase required for protection by dexamethasone was similar. This finding would be suggestive of the fact that the mechanisms by which dexamethasone causes a complete protection against NEC may be mediated by increasing the plasma activity. Other mechanisms have been proposed such as facilitating the maturation of the small bowel. As discussed, other factors such as hypoxia, endotoxins, TNF alpha, and enternal feeding have been suggested to be contributing agents of NEC development. Many of these factors and procedures are known to increase in PAF. We have suggested a mechanism to explain the increase in PAF formation as caused LPS, TNF alpha, and interleukins being the inhibition of the secretion of PAF-AH by macrophages. Our previous reports on the mechanisms involve in the prevention of NEC by glucocorticoids and the reported findings that human recombinant PAF-acetylhydrolase can prevent NEC provide further support for a central role for PAF in NEC development. Furthermore, the presence of a high PAF biosynthetic activity in the neonatal intestine affords an explanation as to why this tissue is highly susceptible to this disease.

Subcutaneous administration of CAMPATH-1H: clinical and biological outcomes

OBJECTIVE

A 24 week study of subcutaneous (sq) dosing with titration of CAMPATH-1H (C1H) dose against the circulating CD4+ T cell count in patients with rheumatoid arthritis (RA) was undertaken to examine the safety, biologic activity, and clinical efficacy of this approach.

METHODS

All patients met American Rheumatism Association (ARA) criteria for active RA. Patients received either 0.5 or 1.0 mg of C1H subcutaneously twice per week; dosing could be doubled after the first 8 weeks of treatment and subsequently following 4 week dose intervals for lack of clinical efficacy, but was discontinued any time the CD4+ T cell count fell below 400/mm3. Patients were evaluated weekly for 2 weeks and then biweekly for clinical and laboratory variables of safety, biological activity, and disease activity.

RESULTS

Ten patients were treated, 6 in the 0.5 mg cohort and 4 in the 1.0 mg cohort. Four of ten patients had a 20% modified Paulus response (2 in each cohort) while taking drug; there were minimal side effects, primarily limited to local reaction at the injection site. All patients had a > 50% drop in circulating CD4+ T cells within the first 2 weeks of therapy, with no further significant reduction; only 1/6 patients in the 0.5 mg cohort had dose limiting CD4+ T cell depression vs 2/4 in the 1.0 mg cohort. All patients developed antibodies to C1H. Appearance of anti-C1H was temporarily associated with a halt in further reduction of CD4+ T cell count despite continued C1H administration.

CONCLUSION

Subcutaneous administration of C1H in low doses (0.5 mg biweekly) was well tolerated and did not result in dose limiting CD4+ T cell depletion in 5 of 6 patients. Clinical efficacy was observed in some patients but could not be maintained, possibly due to the production of anti-C1H antibodies.

Effects of transforming growth factors on dopaminergic neurons in culture

It was recently reported that TGF-beta 1 either had no significant effect on or increased the survival of dopaminergic neurons in culture. TGF-beta 2 and TGF-beta 3 were reported to cause increased survival or to greatly inhibit survival. The transforming growth factors are a highly pleiotropic group of compounds, and the above results suggest that their actions may be critically dependent on the conditions of the assay. We have therefore tested these compounds under optimal conditions of culture, in a medium containing a low (2.5%) concentration of fetal bovine serum. TGF-beta 2 and 3 inhibited neuronal (MAP2-pos) survival only at the highest concentration (10 ng/ml) tested, while inhibition of survival of dopaminergic neurons was observed at 1.0 and 10 ng/ml. These results therefore suggest that the inhibitory action of TGF-beta 2 and 3 on the survival of dopaminergic neurons in culture, under the experimental conditions outlined, may be relatively specific.

Platelet-activating factor (PAF) and PAF acetylhydrolase activity in rat uterus and placenta during the late stages of pregnancy

We evaluated the roles of platelet-activating factor (PAF) and PAF-acetylhydrolase (PAF-AH) activity in late pregnancy. Uterine and placental concentrations of PAF were determined by the washed rabbit platelet aggregation bioassay. Uterine, placental, and plasma PAF-AH activities were also assayed. PAF concentration in the uterus increased 4-fold between Days 15 and 21 of pregnancy. PAF was also determined in the placenta on Days 15 and 21. In contrast to findings in the uterus, the concentration in the placenta was decreased by 75%. Platelet aggregation caused by uterine and placental PAF was inhibited by the PAF receptor antagonists CV-3988 and TCV-309. Plasma and uterine PAF-AH activities decreased significantly between Days 15 and 21. In contrast, the placental PAF-AH activity significantly increased during this same time period. On the basis of these findings, it is suggested that the PAF concentration in the uterus and placenta may be regulated by intracellular PAF-AH and/or plasma PAF-AH activities. Increased PAF activity in the pregnant rat uterus may be related to the initiation of labor due to its known effect on myometrial contraction. Decreased PAF concentration in the placenta may contribute to the fetoplacental circulation due to its known hypotensive activity and the increase in vascular permeability.

Metabolism of platelet-activating factor in rat epididymal spermatozoa

A role for platelet-activating factor (PAF) in sperm function has been proposed. In the present investigation the metabolism of PAF was examined in sperm and epididymal tissue. The major regulatory enzymes for the synthesis of PAF via the de novo pathway have been established in spermatozoa; these include acetyltransferase and cholinephosphotransferase specific for PAF biosynthesis. De novo acetyltransferase activity for PAF biosynthesis in spermatozoa was significantly higher than that of the acetyltransferase of the remodeling pathway. A metabolic pathway was described for the catabolism of PAF in sperm, involving PAF-acetylhydrolase (-AH), lysophospholipase D, and a phosphohydrolase. An isozyme of PAF-AH similar to that reported in sera was also demonstrated in epididymal fluid and tissue. This isozyme was distinctly different from that found in the spermatozoa. The partial inactivation of PAF-AH by the vaginal pH, and/or its detachment from sperm during migration to the site of fertilization, may allow increased motility and migration to the site of fertilization. It is suggested that a decapacitation factor previously described may be related to PAF-AH.

Effect of dexamethasone on rat plasma platelet activating factor acetylhydrolase during the perinatal period

It has been previously reported that the administration of dexamethasone (DEX) to adult rats increases the activity of plasma platelet-activating factor acetylhydrolase (PAF-AH) and prevents the development of intestinal necrosis caused by platelet activating factor (PAF) injection. In this report, we examined the effect of DEX administration on plasma PAF-AH activity during the perinatal period. Timed-pregnant rats received DEX (0.2-1.0 mg/kg/d) or normal saline (controls) on days 16-18 (early group) or days 18-20 (late group) of gestation. Maternal plasma PAF-AH activity was lower in late gestation than in postpartum period (P < 0.001). Fetal and neonatal plasma PAF-AH activity was higher than maternal values (P < 0.05). No changes of PAF-AH activity were seen in maternal, fetal or neonatal plasma after prenatal DEX administration at the aforementioned doses. A higher dose of DEX (1.3 mg/kg/d x 4d) or cortisone (200 mg/kg/d) produced an elevation of maternal plasma PAF-AH activity (DEX 79.2+/-3.0, cortisone 70.5+/-1.9 vs. controls 49.4+/-2.3 nmol/min/ml, P < 0.01), but resulted in a high fetal mortality. Treatment of newborn rats with DEX (0.5 mg/kg/d) on days 1-3 after birth, increased plasma PAF-AH activity on day 4 (DEX 292+/-5 versus controls 140+/-9 nmol/min/ml, P < 0.001) and day 6 (DEX 302+/-12 versus controls 136+/-6 nmol/min/ml, P < 0.001). Postnatal administration of DEX increases the plasma PAF-AH activity in the rat. Only high doses of prenatal corticosteroids that cause fetal death can elevate maternal plasma PAF-AH activity.

Identification and neuron specific expression of the S182/presenilin I protein in human and rodent brains

Many individuals with familial Alzheimer disease (FAD) have mutations in a gene termed S182 or presenilin I (PS-I). Currently, the PS-I gene product has not been identified and its function remains unknown. Here we report that affinity purified antibodies against the predicted amino acid sequence of the PS-I gene product detected in homogenates of human, mouse, and rat brains a single antigen of approximately 48 kDa. This antigen was also present in immortalized human and mouse neuronal cell cultures. Brain tissue fractionation showed that all PS-I antigen was found in the membrane fraction. In stained tissue sections of mouse central nervous system (CNS), PS-I antigen was found only in neurons throughout brain and spinal cord and was located within cell bodies, axons, and dendrites. Remarkably the relative partition among these three compartments varied dramatically. A striking feature of PS-I expression was its intense concentration in some (but not all) dendrites, at levels substantially above those in the parent perikarya. In most of the cerebrum, PS-I staining in axons was very weak or undetectable. By contrast, many axons in portions of the brainstem and in the spinal cord showed marked PS-I immunoreactivity. Similarly, staining of sections from human temporal cortex showed that PS-I was present mainly in neuronal cell bodies and dendrites. These data show that in the CNS, PS-I is expressed mainly in neurons and suggests that this protein may perform a neuron specific function. The pattern of PS-I expression in the CNS would suggest that the premature neurodegeneration associated with PS-I mutations involves a primary neuronal process rather than a secondary effect of PS-I produced in non-neuronal cells.

Standardized methods to bioassay neurotrophic factors for dopaminergic neurons

The search for specific neurotrophic factors that will eventually be used to reduce or arrest the rate of degeneration of dopaminergic neurons in Parkinson's disease is being pursued by first testing the ability of putative compounds to increase the survival of dopaminergic neurons in primary cultures of the fetal, ventral mesencephalon. This research has intensified in recent years. The experimental procedures used by different laboratories in these studies differ widely, and meaningful comparisons of the results obtained are accordingly difficult to make. Some important experimental variables include the age of the fetal tissue used; the dissection technique used to isolate the ventral mesencephalon; the percentage of dopaminergic neurons present in the culture initially; handling of the tissue during dissection; the technique used to disperse the cells; the use of serum; the technique of plating the cells; the attachment factors used; detachment and loss of cells during the staining procedure; the age of the cultures at the time of analysis; the uneven distribution of cells at the time of analysis and the use of imaging techniques in the analysis. We show that when the E14 rat embryo is used, it is possible to consistently obtain a culture with 20% of tyrosine hydroxylase-positive neurons. Neither the plating density in the range of 7.8 x 10(3) to 1.25 x 10(5) cells/cm2, nor the percentage of serum in the growth medium affected the percentage of cells that expressed TH initially, at 4 or 12 h after plating. When the cells were plated as 25 microliters droplets, called microislands (area approximately 12.5 mm2), and allowed to attach before additional growth medium was added, cell density remained uniform at the center of the microisland for the duration of the culture. Restriction of the analysis of cell survival to the center of the microisland therefore helped to decrease the variability in counting that could occur when cells are dispersed over a larger area. In contrast, in an 8-well chamber slide or 35 mm petri dish, in which the whole area is plated, cell density was consistently higher at the edge (edge effect), versus the centre, by a factor of about three. The use of microisland cultures also has the additional benefit of increasing by a factor of about five the number of individual cultures that can be set up per liter, and a proportionate reduction in the number of animals used per experiment. When the percentage of serum in the growth medium was 0% always, or 10% for the first 12 h, and 0% thereafter, or 10% always, the number of TH-pos neurons per field (using a x 20 objective, column factor 1.25; area 320 microns2) after 5 days in culture (DIV5) was < 1,3-8 and 14-22, respectively. Under the same experimental conditions, the number of neurons (MAP2-positive) per field was 5-8, 18-30 and 45-65 (N = 10 in all cases), respectively. Serum deprivation therefore has a highly deleterious effect on neuronal survival in culture. We suggest that cultures that were exposed to serum at any stage of the experiment, should not be referred to as "serum-free', since even a brief exposure to serum exerts a protective effect on neurons, and especially on dopaminergic neurons. Instead, the percentage and kind of serum used, the exact usage, and the duration of exposure of the cells to serum should be stated. Finally, it is suggested that where possible, an imaging system with manual count and journaling capabilities be used in the analysis. The methods described are illustrated by dose-response curves of the neurotrophic effects of BDNF, NGF-beta and IL-6 versus percentage survival on dopaminergic neurons, when grown in serum-free medium throughout.

Changes in glycerophospholipid profile in experimental nephrotic syndrome

We investigated changes in the glycerophospholipids in kidney tissue and its various intracellular fractions in rats with nephrotic syndrome induced by puromycin aminonucleoside. The ethanolamine plasmalogen, 1-O-alk-1'-enyl-2-acyl-GPE (EP), was increased in kidney tissue obtained from the puromycin-treated animals. A similar increase was found in the mitochondria and endoplasmic reticulum (microsomes) of this tissue. These increases were not found in the liver. Since platelet-activating factor (PAF) is known to be produced in increased amounts in inflammatory disorders, it is suggested that the higher plasmalogen found in rat kidneys during experimental nephrotic syndrome might be derived from increased levels of this autacoid. The increase in PAF may also result in the elevation of plasma PAF-acetylhydrolase (AH) activity observed in these animals.

The biochemical role of platelet-activating factor in reproduction

The presence of Co-A independent transacylase activity in amnion cells and the preferential transfer of arachidonic acid to acceptor-ethanolamine plasmalogen provide a satisfactory explanation to the questions raised by the observation that arachidonate-enriched ethanolamine plasmalogen increases in amnion late in gestation without alteration in the total amount of ethanolamine glycerophospholipids. The proposed mechanism also serves as a link between the observed changes in glycerophospholipid composition and the generation of PAF. We have emphasized a role for PAF in fetal lung maturation, the initiation and maintenance of parturition, and in certain complications associated with a premature delivery. Although PAF is known to be the most potent lipid mediator yet described and its importance in reproductive biology is well documented, it is our view that these events cannot be attributed solely to PAF and in all likelihood a number of autacoids participate in these processes.

Analysis of hypermutation in immunoglobulin heavy chain passenger transgenes

Somatic hypermutation of immunoglobulin (Ig) genes plays a critical role in the maturation of the human antibody response. The molecular basis of this important process is, however, unknown. To identify cis-acting sequences that initiate and target hypermutation, we have made three minitransgenes containing different portions of an Ig heavy chain (IgH) locus. Each transgene is a passenger, bearing a nonsense mutation preventing its translation; thus, transgene mutations reflect the endogenous mutational process and are not subject to affinity selection. To study transgenes after their circulation through the compartment associated with hypermutation in vivo, we rescued B cells as hybridomas after hyperimmunizing mice with the hapten 4-hydroxy-3-nitrophenyl acetyl (NP). Hybridoma transgene and endogenous variable regions were amplified by polymerase chain reaction, subcloned, and sequenced. Endogenous anti-NP VDJ regions show the expected, at times extensive degree of base substitution. In mice bearing the smallest construct, which includes 2.4 kb of 5' IgH sequences, a rearranged VDJ region, the 5' matrix attachment region, and the intron enhancer, one of four evaluable hybridomas demonstrates two base substitutions in the V segment of one transgene copy. The two larger constructs include additional 3' IgH sequences (an alpha constant region and the 3' enhancer) and either the original VDJ segment or a substituted T cell receptor beta segment. Ten hybridomas derived from mice bearing these larger constructs demonstrate no evidence of targeted mutation, despite demonstrable transgene transcription in all hybridomas. In our system, mutation of a rearranged VDJ segment and surrounding promoter/enhancer regions is not increased by the juxtaposition of a constant region segment and the IgH 3' enhancer.

Repopulation of blood lymphocyte sub-populations in rheumatoid arthritis patients treated with the depleting humanized monoclonal antibody, CAMPATH-1H

Patients with severe rheumatoid arthritis who had failed treatment with conventional therapies were treated with a course of five or 10 daily intravenous infusions of CAMPATH-1H, a humanized antibody against the CD52 antigen, resulting in profound depletion of peripheral blood mononuclear cells. During the subsequent 18 months, lymphocytes were analysed for sub-populations by fluorescence-activated cell sorter (FACS) and for proliferation in response to polyclonal T-cell stimulation with anti-CD3 or staphylococcal enterotoxin B (SEB). Treatment resulted in almost complete depletion of lymphocytes from the blood followed by gradual repopulation. CD16+ natural killer (NK) cells and CD14+ monocytes returned to pretreatment levels within 1-2 months. CD19+ B cells returned to within 50% of pre-treatment levels by day 66 and to within normal range by day 150, whereas CD8+ T cells recovered to 50% of pretreatment levels by day 66, but did not show any further increase during the rest of the study period. The most profound effects were on the CD4+ T lymphocyte sub-population, as the mean CD4+ count did not increase above 20% of pre-treatment level at any time during the study period (550 days), at all the doses tested. The T cells which initially repopulated the blood 1-2 months after treatment, nearly all expressed the activation markers human leucocyte antigen (HLA)-DR and CD45RO, although the percentage of T cells expressing these molecules gradually declined to normal levels over time. Proliferative responses to polyclonal T-cell stimulation (anti-CD3 and SEB) were also significantly reduced in the first few months after treatment, but recovered to pre-treatment levels by day 250. The relationship between these observations and the clinical response is discussed.

CAMPATH-1H in rheumatoid arthritis--an intravenous dose-ranging study

Forty-one patients with active and refractory rheumatoid arthritis(RA) received a total of 100, 250 or 400 mg of CAMPATH-1H (CAMPATH is a trademark of Glaxo-Wellcome group companies, registered in the US Patent and Trademark Office) over 5 or 10 days in an open, uncontrolled study. Following therapy, patients were monitored for adverse effects and disease activity for 6 months. Therapy was associated with prolonged peripheral blood lymphopenia in all dosing cohorts. During the month immediately following therapy, lymphopenia was most profound in the 400 mg cohorts. The first dose of monoclonal antibody (Mab) was associated with a 'flu'-like syndrome, more pronounced at higher initial doses. One patient developed haemolytic-uraemic syndrome. There were a number of dose-related infections during the early post-treatment period and one fatal opportunistic infection which followed additional immunosuppressive therapy. Antiglobulin responses developed in 9 of 31 patients tested. The majority of patients showed symptomatic improvement following therapy and 20% of patients maintained a 50% Paulus response at 6 months, all of whom were in the 250 or 400 mg cohorts. CAMPATH-1H appears to be an effective treatment for RA. Allowing for the small number of patients treated, infections were more common with higher doses, although this was not true for adverse events overall, and therapeutic responses were more sustained at higher dosing levels. The broad specificity of CAMPATH-1H may be appropriate for the immunotherapy of RA and future studies should aim to define a dose with an optimal therapeutic ratio.

The absence of ongoing immunoglobulin gene hypermutation suggests a distinct mechanism for c-myc mutation in endemic Burkitt's lymphoma

PURPOSE

Burkitt's lymphoma is a malignancy of mature, immunoglobulin (Ig)-bearing B cells characterized by translocation between c-myc and Ig gene loci. A role for the juxtaposed Ig genes in the mutation and deregulation of c-myc expression typical of endemic Burkitt's lymphoma (eBL) has been proposed, but never proven. Our objective was to determine whether Ig gene hypermutation is ongoing in eBL.

METHODS

We isolated Ig heavy-chain sequences from K962 eBL tumor cells using reverse transcription and polymerase chain reaction (PCR) amplification. The PCR product was ligated into Bluescript II vectors. Multiple subclones were sequenced and the variable regions were compared for evidence of ongoing Ig hypermutation.

RESULTS

Six total single base substitutions were observed within four of the nine subclones studied. Four substitutions resulted in amino acid changes and two were silent. There was no clustering of mutations in hypervariable regions, or a high incidence of amino acid replacement or link substitutions, all of which are characteristic of Ig hypermutation. The observed mutations occurred at a rate consistent with Taq polymerase error.

CONCLUSIONS

Our data indicate that in the eBL tumor sample K962, the mechanism underlying c-myc mutation is distinct from that which gives rise to Ig hypermutation.